Tom Andersen

Utvalgte publikasjoner:

Persson, Jonas; Wojewodzic, Marcin; Hessen, Dag Olav & Andersen, Tom (2011). Increased risk of phosphorus limitation at higher temperatures for Daphnia magna. Oecologia.  ISSN 0029-8549.  165(1), s 123- 129 . doi: 10.1007/s00442-010-1756-4

Ptacnik, Robert; Andersen, Tom; Brettum, Pål; Lepistö, Liisa & Willén, Eva (2010). Regional species pools control community saturation in lake phytoplankton. Proceedings of the Royal Society of London. Biological Sciences.  ISSN 0962-8452.  277(1701), s 3755- 3764 . doi: 10.1098/rspb.2010.1158

Ptacnik, Robert; Andersen, Tom & Tamminen, Timo (2010). Performance of the Redfield Ratio and a Family of Nutrient Limitation Indicators as Thresholds for Phytoplankton N vs. P Limitation. Ecosystems (New York. Print).  ISSN 1432-9840.  13(8), s 1201- 1214 . doi: 10.1007/s10021-010-9380-z

Spilling, K; Tamminen, Timo; Andersen, Tom & Kremp, Anke (2010). Nutrient kinetics modeled from time series of substrate depletion and growth: dissolved silicate uptake of Baltic Sea spring diatoms. Marine Biology.  ISSN 0025-3162.  157(2), s 427- 436 . doi: 10.1007/s00227-009-1329-4

Andersen, Tom; Carstensen, Jacob; Hernández-Garcia, Emilio & Duarte, Carlos M. (2009). Ecological thresholds and regime shifts: approaches to identification. Trends in Ecology & Evolution.  ISSN 0169-5347.  24(1), s 49- 57 . doi: 10.1016/j.tree.2008.07.014

Elser, James J.; Andersen, Tom; Baron, Jill S.; Bergström, Ann-Kristin; Jansson, Mats; Kyle, Marcia; Nydick, Koren R. et al. (2009). Shifts in Lake N:P Stoichiometry and Nutrient Limitation Driven by Atmospheric Nitrogen Deposition. Science.  ISSN 0036-8075.  326(5954), s 835- 837 . doi: 10.1126/science.1176199

Hessen, Dag Olav; Andersen, Tom; Larsen, Søren; Skjelkvåle, Brit Lisa & Wit, Heleen A. de (2009). Nitrogen deposition, catchment productivity, and climate as determinants of lake stoichiometry. Limnology and Oceanography.  ISSN 0024-3590.  54(6), s 2520- 2528

Moller, JK; Carstensen, J; Madsen, H & Andersen, Tom (2009). Dynamic two state stochastic models for ecological regime shifts. Environmetrics.  ISSN 1180-4009.  20(8), s 912- 927 . doi: 10.1002/env.962

Halvorsen, Rune; Andersen, Tom & Moen, Asbjørn (2008). Kunnskapsgrunnlaget for økoklinen akkumulering av organisk materiale (AO): Betingelser for akkumulering av organisk materiale og for forekomst av organisk mark/bunn, I: Rune, Halvorsen (red.),  Artikkelsamling.  Artsdatabanken.  ISBN 978-82-92838-09-9.  Artikkel 20.  s 82 - 85

Ptacnik, R; Lepisto, L; Willen, E; Brettum, P; Andersen, Tom; Rekolainen, S; Solheim, AL et al. (2008). Quantitative responses of lake phytoplankton to eutrophication in Northern Europe. Aquatic Ecology.  ISSN 1386-2588.  42 . doi: 10.1007/s10452-008-9181-z

Sterner, Robert W.; Andersen, Tom; Elser, James J.; Hessen, Dag Olav; Hood, James M.; McCauley, Edward & Urabe, Jotaro (2008). Scale-dependent carbon:nitrogen:phosphorus seston stoichiometry in marine and freshwaters. Limnology and Oceanography.  ISSN 0024-3590.  53(3), s 1169- 1180

Andersen, Tom; Færøvig, Per-Johan & Hessen, Dag Olav (2007). Growth rate versus biomass accumulation: Different roles of food quality and quantity for consumers. Limnology and Oceanography.  ISSN 0024-3590.  52, s 2128- 2134

Andersen, Tom; Saloranta, Tuomo M & Tamminen, T (2007). A statistical procedure for unsupervised classification of nutrient limitation bioassay experiments with natural phytoplankton communities. Limnology and Oceanography : Methods.  ISSN 1541-5856.  5

Blikstad, Camilla; Rohrlack, Thomas; Andersen, Tom; Skulberg, Olav & Edvardsen, Bente (2007). Seasonal dynamics and depth distribution of Planktothrix spp. in Lake Steinsfjorden (Norway) related to environmental factors. Journal of Plankton Research.  ISSN 0142-7873.  29, s 471- 482 . doi: 10.1093/plankt/fbm036

Olsen, Yngvar; Andersen, Tom; Gismervik, Ingrid & Vadstein, Olav (2007). Protozoan and metazoan zooplankton-mediated carbon flows in nutrient-enriched coastal planktonic communities. Marine Ecology Progress Series.  ISSN 0171-8630.  331, s 67- 83

Saloranta, Tuomo M & Andersen, Tom (2007). MyLake - A multi-year lake simulation model code suitable for uncertainty and sensitivity analysis simulations. Ecological Modelling.  ISSN 0304-3800.  207, s 45- 60 . doi: 10.1016/j.ecolmodel.2007.03.018

Tamminen, T & Andersen, Tom (2007). Seasonal phytoplankton nutrient limitation patterns as revealed by bioassays over Baltic Sea gradients of salinity and eutrophication. Marine Ecology Progress Series.  ISSN 0171-8630.  340, s 121- 138

Andersen, Tom; Bjørndalen, Knut & Brabrand, Åge (2006). Foregår det interngjødsling i Vansjø?. Vann.  ISSN 0042-2592.  41(4), s 396- 407
Hessen, Dag Olav; Faafeng, Bjørn; Brettum, Pål & Andersen, Tom (2006). Nutrient enrichment and planktonic biomass ratios in lakes. Ecosystems (New York. Print).  ISSN 1432-9840.  9, s 516- 527

Olsen, Yngvar; Agusti, Susana; Andersen, T.; Duarte, Carlos; Gasol, J. M.; Gismervik, Ingrid; Heiskanen, Anna-Stiina. et al. (2006). A comparative study of responses in planktonic food web structure and function in contrasting European coastal waters exposed to experimental nutrient addition. Limnology and Oceanography.  ISSN 0024-3590.  51, s 488- 503

Donali, Espen Bang; Brettum, P; Kaste, O; Lovik, J; Lyche-Solheim, A & Andersen, Tom (2005). Pelagic response of a humic lake to three years of phosphorus addition. Canadian Journal of Fisheries and Aquatic Sciences.  ISSN 0706-652X.  62

Andersen, Tom (2004). Dynamic energy budget representations of stoichiometric constraints on population dynamics. Ecology.  ISSN 0012-9658.  85(5), s 1230- 1243

Andersen, Tom; Elser, JJ & Hessen, Dag Olav (2004). Stoichiometry and population dynamics. Ecology Letters.  ISSN 1461-023X.  7, s 884- 900

Andersen, Tom (2003). Is phosphorus limitation of planktonic heterotrophic bacteria and accumulation of degradable DOC a normal phenomenon in phosphorus-limited systems? A microcosm study. FEMS Microbiology Ecology.  ISSN 0168-6496.  46(3), s 307- 316

Andersen, Tom & Gismervik, Ingrid (2003). Beyond bulk properties: Responses of coastal summer plankton communities to nutrient enrichment in the northern Baltic Sea. Limnology and Oceanography.  ISSN 0024-3590.  48(1), s 189- 209

Hessen, Dag Olav; Andersen, Tom; Brettum, Pål & Faafeng, Bjørn Andreas (2003). Phytoplankton contribution to sestonic mass and elemental ratios in lakes. Limnology and Oceanography.  ISSN 0024-3590.  48, s 1289- 1296

Vadstein, Olav; Olsen, Lasse Mork; Busch, A.; Andersen, Tom & Reinertsen, Helge (2003). Is phosphorus limitation of heterotrophic bacteria and accumulation of degradable DOC a normal phenomenon in phosphorus limited systems? A microcosm study. FEMS Microbiology Ecology.  ISSN 0168-6496.  46, s 307- 316

Stabell, T.; Andersen, Tom & Klaveness, Dag (2002). Ecological significance of endosymbionts in a mixotrophic ciliate - an experimental test of a simple model of growth coordination between host and symbiont.. Journal of Plankton Research.  ISSN 0142-7873.  24(9), s 889- 899

Olsen, Yngvar; Reinertsen, Helge; Andersen, Tom; Gismervik, Ingrid; Duarte, Carlos; Agusti, Susana; Stibor, Herwig et al. (2001). Comparative analysis of food webs based on flow networks: effects of nutrient supply on structure and function of coastal plankton communities. Continental Shelf Research.  ISSN 0278-4343.  (21), s 2043- 2053

Gismervik, Ingrid; Andersen, Tom & Vadstein, Olav (1996). Pelagic Food Webs and Eutrophication of Coastal Waters: Impact of Grazers on Algal Communities.. Marine Pollution Bulletin.  ISSN 0025-326X.  33(1-6), s 22- 35  

• Eliassen, Lasse Krøger; Garvang, Even Sletteng; Andersen, Tom; Riemann, Lasse & Titelman, Josefin (2026). Metabarcoding and biomass quantification reveal seasonal parasite associations in copepods. Limnology and Oceanography. ISSN 0024-3590. 71(2). doi: 10.1002/lno.70327. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Parasites are important members of ecosystems, and recent metabarcoding efforts have revealed an abundance of microbial eukaryotic parasites in copepods. However, a putative linkage to host community biomass and composition has not been addressed. We performed zooplankton tows monthly for 2 yr at five stations in the Oslofjord, Norway. The samples were cleared of larger, non‐copepod zooplankton and contained mainly copepods and are henceforth referred to as copepod community samples. Metabarcoding was used to detect microbial eukaryotic parasites in the copepod community samples. We also metabarcoded water samples from one of the stations. Copepods were identified and their biomasses were estimated at three of the stations for 1 yr. Calanus spp. dominated biomass in winter, whereas Temora longicornis and other smaller, short‐lived coastal copepods prevailed during summer. Seasonality in the copepod community was less apparent in the deep waters (200 m) where larger, long‐lived copepods abound. The alveolate parasites Hematodinium and Chromidina were detected at most stations throughout the year and occupied a large proportion of the total reads. Although the microbial eukaryotic community in the copepod community samples reflected the seasonal copepod dynamics, common alveolate parasites (e.g., Syndinium , Blastodinium , and apostome ciliates) appeared year‐round. Co‐occurrence analysis suggested several pair‐wise associations between taxa of microbial eukaryotes and copepods. Parasites are a universal component of copepods in this fjord system and seem well‐adapted to seasonal fluctuations in host community composition. We hypothesize that the parasites may have host ranges that incorporate perennial copepods to maintain their presence in seasonally fluctuating environments.

• Berezovski, Aleksandr; Hessen, Dag Olav; Børseth, Hanne Halkjelsvik & Andersen, Tom (2025). Optical properties of dissolved organic matter along a salinity gradient from a boreal river estuary to open coastal waters. Marine and Freshwater Research. ISSN 1323-1650. 76(11). doi: 10.1071/mf24244. Fulltekst i vitenarkiv Vis sammendrag

  Context Water darkening is an increasingly relevant problem affecting many coastal ecosystems, and it is exacerbated by human activity and climate change. Aims To determine the spectral, isotopic, and quantitative changes in coloured dissolved organic matter (CDOM) across a salinity gradient from the Glomma River to the outer Oslofjord. Methods CDOM absorbance was measured on a spectrophotometer and organic carbon in the water column was analysed using stable isotopes. Key results Spectral slope and CDOM absorption at 443 nm decreases linearly with an increasing salinity. CDOM absorption exhibited significant variations, with low-salinity samples showing higher light absorption per unit of carbon, but little seasonal variations. δ13C of TOC analysis showed a strong positive correlation with salinity. Conclusion Dissolved organic matter optical characteristics of coastal waters are tightly linked to CDOM. The distance to the river mouth and to the shore are some of the most important factors affecting water clarity. The δ13C of TOC analysis indicated a linear transition from terrestrial to marine carbon sources. Implications The study has shown how coastal darkening can be an important ecological issue mainly in near-coastal areas and describes valuable diagnostic tools for tracking it.

• Berezovski, Aleksandr; Hessen, Dag Olav & Andersen, Tom (2025). Photon budgets and the relative effects of CDOM and pigment absorptions on primary production along a coastal salinity gradient. Frontiers in Photobiology. 2. doi: 10.3389/fphbi.2024.1452747. Fulltekst i vitenarkiv Vis sammendrag

  The study highlights the critical role of CDOM in coastal light attenuation and its impact on primary production (PP). We investigated the spectral attenuation of light due to water, phytoplankton pigments, detritus and coloured dissolved organic matter (CDOM) along a salinity gradient in the outer Oslofjord, Norway. By examining the effects of these components across different seasons, we aimed to elucidate their relative contributions to light absorption and PP. The findings suggest that increased terrestrial CDOM inputs, driven by climate, changed atmospheric deposition and land-use changes, could significantly affect coastal ecosystems by altering light attenuation and consequently PP and potentially leading to other ecological pressures. CDOM consistently dominated light absorption across all stations and seasons, contributing 50%–80% of the total absorption of photosynthetically active radiation. The absorption by CDOM and detritus decreased with increasing salinity, while phytoplankton absorption followed a seasonal succession. PP estimates show high seasonal variability from maximums in June to minimums in November, mainly attributed to, changes in seasonal light availability and phytoplankton biomass, followed by light attenuation by CDOM and differences in quantum yields of photosystem II (PSII). Nutrient analysis showed a seasonal pattern, with the highest nitrogen concentrations in November and depletion during more productive seasons, as well as conservative mixing throughout the salinity gradient. CDOM absorption played substantial, albeit not leading, role in influencing PP estimates, derived from a bio-optical model. CDOM was the main determinant of light attenuation across most wavelegnths.

• Garvang, Even Sletteng; Heuschele, Jan David; Konestabo, Heidi Sjursen; Andersen, Tom; Riemann, Lasse & Titelman, Josefin (2025). Parasite infection shapes the pathobiome and behavior of marine zooplankton. Limnology and Oceanography Letters. 11(1). doi: 10.1002/lol2.70078. Fulltekst i vitenarkiv Vis sammendrag

  When assessing the total impact of disease in a host, it is important to consider not only the disease‐carrying agent but also all symbionts, as they affect and are affected by the course of disease. This concept of a pathobiome is increasingly recognized in disease ecology, but is not well‐investigated in natural systems. Copepods are key organisms in marine ecosystems and host a variety of symbionts, including bacteria and eukaryotic parasites. We investigated the impact of a taxonomically uncertain yellow‐hyphal parasite (YHP) on its copepod host Calanus helgolandicus with an incubation experiment, comparing survival, behavior, and microbiomes of uninfected and infected hosts. Infected hosts suffered higher mortality, and altered behavior which can increase predation risk. The microbiomes differed between infected and uninfected hosts, likely caused by a combination of direct effects of infection, and environmental effects driven by parasite‐induced behavioral change. We identified several potential contributing taxa to the Calanus ‐YHP pathobiome using model‐based ordination.

• Eliassen, Lasse Krøger; Altin, Dag; Andersen, Tom; Riemann, Lasse; Dunthorn, Micah & Titelman, Josefin (2025). Long Term Copepod Culture Houses a Rich Microbial Eukaryotic Community Including New and Known Symbionts. Journal of Eukaryotic Microbiology. ISSN 1066-5234. 72(6). doi: 10.1111/jeu.70053. Fulltekst i vitenarkiv Vis sammendrag

  Copepods, dominant marine zooplankton, are hosts to microbial eukaryotic symbionts, but the copepod eukaryome remains largely unexplored. We used 18S rRNA gene primers with reduced metazoan amplification to identify microbial eukaryotes in a culture of Calanus finmarchicus (Copepoda). Samples were taken from the inlet water (99.5% of reads from non‐copepod sources) and the contents of the culture, which included ambient water (99.7%), bulk (many crushed copepods, 60.2%), individual copepods (1%–41%, mean = 7.4), and bulk fecal pellets (74%). The microbial eukaryotic community in the culture differed from the inlet water. The culture contained saprotrophs and bacterivores typical of eutrophic aquacultures and known parasites of copepods. Individual copepod eukaryomes varied in richness (8–33 operational taxonomic units, mean = 16.1) and revealed variation in non‐copepod read yields related to specific taxa. Perkinsea, not previously reported in copepods, as well as Ascomycota and Basidiomycota (Fungi), formed the core eukaryome (found in > 90% of individuals), indicating potentially important symbiosis. The small eukaryome, relative to reported microbiomes in C. finmarchicus , suggests that ecological inferences from microbiomes, which largely address bacteria, are not readily applicable to the eukaryotic microbes. The study underpins the need for investigations of eukaryomes.

• Vindenes, Yngvild; Broch, Catharina; Andersen, Tom; Hessen, Dag Olav & Ergon, Torbjørn (2025). Understanding the role of ageing in the thermal responses of life history and fitness in Daphnia magna. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 292(2051). doi: 10.1098/rspb.2025.0430. Fulltekst i vitenarkiv Vis sammendrag

  The current climate warming has raised concerns that increased rates of ageing will lead to reduced fitness and population viability in ectotherms. However, it is currently not known whether temperature effects on the rate of ageing mainly reflect a change in pace of life or changes in the strength of ageing in the life history. Evaluating this question requires that ageing in different temperatures is compared on the same intrinsic pace-standardized time scale. We present results from a laboratory experiment with Daphnia magna , recording complete life histories of 240 individuals from four clonal lines at six temperatures (5°C to 30°C). For each clone and temperature, we calculated measures of pace and shape of ageing in survival and reproduction. Fitness (long-term population growth rate) and mean lifetime reproduction were calculated using matrix population models. Our results highlight three main points: (i) lifespan is not a good predictor of temperature effects on ageing; (ii) there is no strong consistent effect of temperature on shape of ageing; and (iii) within temperature, the shape of ageing was positively correlated with fitness. Hence, lower fitness and population viability of ectotherms in warmer environments may be driven by factors other than increased ageing rates.

• Fon, Mathias; Supraha, Luka; Andersen, Tom; Uhlig, Silvio & Edvardsen, Bente (2024). Optimal growth conditions of the haptophyte Chrysochromulina leadbeateri causing massive fish mortality in Northern Norway. Harmful Algae. ISSN 1568-9883. 139. doi: 10.1016/j.hal.2024.102709. Fulltekst i vitenarkiv Vis sammendrag

  The haptophyte Chrysochromulina leadbeateri formed the most devastating fish-killing algal bloom ever recorded in Norway, in May and June 2019. The bloom resulted in the death of 14,500 tons of farmed salmon in Nordland and Troms Counties and large economic losses to the aquaculture industry in the region. Fish mortalities due to blooms of this species have occurred before in this region in 1991. Environmental conditions promoting bloom formation and growth of C. leadbeateri are, however, still poorly understood. Here we investigated growth as a function of temperature, salinity and irradiance in combinations using a high throughput experimental set-up. Three strains of C. leadbeateri isolated from the 2019 event and an earlier bloom in 1991 were examined. The highest maximal specific growth rate was found at salinities 28–30 and temperatures between 13 and 15 °C, with growth rate generally increasing with irradiance. The upper temperature tolerance for growth for all strains was at 17–19 °C. Further, analyses of the geographical distribution of C. leadbeateri in previous DNA-based studies compiled in the metaPR2 database revealed several ribotypes, and that a cold-water ribotype of C. leadbeateri caused both the 1991 and 2019 blooms.

• Garvang, Even Sletteng; Eliassen, Lasse Krøger; Titelman, Josefin & Andersen, Tom (2024). Outbreak conditions and impacts of parasites in copepod populations. Ecosphere. 15(12), s. 1–18. doi: 10.1002/ecs2.70093. Fulltekst i vitenarkiv
• Volpe, Charlotte; Nymark, Marianne; Andersen, Tom; Winge, Per; Lavaud, Johann & Vadstein, Olav (2024). Skeletonema marinoi ecotypes show specific habitat-related responses to fluctuating light supporting high potential for growth under photobioreactor light regime. New Phytologist. ISSN 0028-646X. 243(1), s. 145–161. doi: 10.1111/nph.19788. Fulltekst i vitenarkiv Vis sammendrag

  * Diatoms are a diverse group of phytoplankton usually dominating areas characterized by rapidly shifting light conditions. Because of their high growth rates and interesting biochemical profile, their biomass is considered for various commercial applications. This study aimed at identifying strains with superior growth in a photobioreactor (PBR) by screening the natural intraspecific diversity of ecotypes isolated from different habitats. We investigated the effect of PBR light fluctuating on a millisecond scale (FL, simulating the light in a PBR) on 19 ecotypes of the diatom Skeletonema marinoi isolated from the North Sea–Baltic Sea area. * We compare growth, pigment ratios, phylogeny, photo-physiological variables and photoacclimation strategies between all strains and perform qPCR and absorption spectra analysis on a subset of strains. * Our results show that the ecotypes responded differently to FL, and have contrasting photo-physiological and photoprotective strategies. The strains from Kattegat performed better in FL, and shared common photoacclimation and photoprotection strategies that are the results of adaptation to the specific light climate of the Kattegat area. * The strains that performed better with FL conditions had a high light (HL)-acclimated phenotype coupled with unique nonphotochemical quenching features. Based on their characteristics, three strains were identified as good candidates for growth in PBRs.

• Giebichenstein, Julia; Andersen, Tom; Varpe, Øystein; Gabrielsen, Geir W. & Borgå, Katrine (2024). Little seasonal variation of mercury concentrations and biomagnification in an Arctic pelagic food web. Progress in Oceanography. ISSN 0079-6611. 231. doi: 10.1016/j.pocean.2024.103381. Fulltekst i vitenarkiv Vis sammendrag

  Despite numerous studies on mercury in Arctic biota, data from inaccessible, ice-covered regions − especially during the polar night and late winter − remain scarce. This scarcity results in poor understanding of the seasonal dynamics of mercury within the food web. From the Northern Barents Sea, we quantified total mercury and the dietary descriptors δ15N and δ13C as long-term dietary signals (weeks to months) in biota to a) investigate the seasonal pelagic food web structure, b) seasonality in total mercury concentration, c) and its biomagnification in the food web. Mercury and dietary descriptors were analyzed in copepods, macrozooplankton (krill, amphipods, arrow worms and pteropods) and the fishes, Atlantic cod (Gadus morhua), polar cod (Boreogadus saida) and capelin (Mallotus villosus) during spring, late summer, early,and late winter. Seasonal changes were observed in δ15N values in some macrozooplankton and capelin, and some seasonal variation was observed across the food web with depleted δ13C values in spring and enriched δ13C values in late summer. Mercury concentrations were lower (range: 2.49 ng/g dw in the krill Thyssanossa sp. – 70.55 ng/g dw in the pelagic pteropod Clione limacina) than reported from other parts of the Arctic. We found a positive linear relationship between mercury and relative trophic position represented by δ15N, i.e., biomagnification, during all seasons, except in early winter. As Clione limacina likely had different turnover rates for mercury and stable isotopes resulting in low δ15N, but high mercury concentrations in early winter, compared to the other species in the food web, the pteropod was omitted from the regression. By omitting Clione limacina, biomagnification was similar across all seasons (R2adj = 0.45). Thus, we saw clear mercury biomagnification with consistent and little seasonal variation in this high Arctic marine food web despite large seasonal fluctuations in abiotic and biotic conditions.

• Côté, Marianne; Englund, Göran; Andersen, Tom; Hessen, Dag Olav; Finstad, Anders Gravbrøt & Bélanger, Claude [Vis alle 7 forfattere av denne artikkelen] (2024). Towards modeling data-poor lakes at the regional scale using parameters from data-rich lakes and relationships to lake characteristics. INLAND WATERS. ISSN 2044-2041. 13(3), s. 388–401. doi: 10.1080/20442041.2023.2265798. Fulltekst i vitenarkiv Vis sammendrag

  Lakes pivotal for recreation and economically relevant activities are often remote and not well studied, which hinders the application of predictive lake models for their management. Here, we provide an approach to simulate—by means of the process-oriented model MyLake—water temperature, ice cover duration, dissolved oxygen, and light attenuation in 198 data-poor lakes based on parameters obtained for a subgroup of 12 data-rich lakes and morphometric data. Specifically, the model is first calibrated using a genetic algorithm on well-studied lakes. Simple relationships between the fitted parameters and lake-catchment morphometric properties are then derived, and the results of simulations using fitted and derived parameters are compared. The loss in goodness-of-fit, expressed as root mean square error (RMSE) incurred by using estimated rather than calibrated parameters, is 0.17 °C for water temperature and 0.82 mg L−1 for dissolved oxygen. These general relationships are then used to provide the model parameters for 198 data-poor lakes distributed throughout Sweden and to model these lakes. Overall, this proof of concept allows simulating lakes selected based on their relevance for lake management rather than based on the availability of extensive field datasets.

• Opdal, Anders Martin Frugård; Lindemann, Christian; Andersen, Tom; Hessen, Dag Olav; Fiksen, Øyvind & Aksnes, Dag Lorents (2024). Land use change and coastal water darkening drive synchronous dynamics in phytoplankton and fish phenology on centennial timescales. Global Change Biology. ISSN 1354-1013. 30(5). doi: 10.1111/gcb.17308. Fulltekst i vitenarkiv Vis sammendrag

  At high latitudes, the suitable window for timing reproductive events is particularly narrow, promoting tight synchrony between trophic levels. Climate change may disrupt this synchrony due to diverging responses to temperature between, for example, the early life stages of higher trophic levels and their food resources. Evidence for this is equivocal, and the role of compensatory mechanisms is poorly understood. Here, we show how a combination of ocean warming and coastal water darkening drive long-term changes in phytoplankton spring bloom timing in Lofoten Norway, and how spawning time of Northeast Arctic cod responds in synchrony. Spring bloom timing was derived from hydrographical observations dating back to 1936, while cod spawning time was estimated from weekly fisheries catch and roe landing data since 1877. Our results suggest that land use change and freshwater run-off causing coastal water darkening has gradually delayed the spring bloom up to the late 1980s after which ocean warming has caused it to advance. The cod appear to track phytoplankton dynamics by timing gonadal development and spawning to maximize overlap between offspring hatch date and predicted resource availability. This finding emphasises the importance of land–ocean coupling for coastal ecosystem functioning, and the potential for fish to adapt through phenotypic plasticity.

• Schultze, Sabrina; Langva, Hilde Kleppe; Wei, Jing; Chatzigeorgiou, Marios; Rundberget, Thomas & Hessen, Dag Olav [Vis alle 9 forfattere av denne artikkelen] (2024). Do DOM quality and origin affect the uptake and accumulation of a lipid-soluble contaminant in a filter feeding ascidian species (Ciona) that can target small particle size classes? Aquatic Toxicology. ISSN 0166-445X. 273. doi: 10.1016/j.aquatox.2024.107026. Fulltekst i vitenarkiv Vis sammendrag

  The widely reported increase of terrestrial dissolved organic matter (terrDOM) in northern latitude coastal areas (“coastal darkening”) can impact contaminant dynamics in affected systems. One potential impact is based on differences in chemical adsorption processes of the molecularly larger terrDOM compared to marine DOM (marDOM) that leads to increased emulsification of lipophilic contaminants with terrDOM. Filter feeders filter large amounts of water and DOM daily and thus are directly exposed to associated contaminants through both respiration and feeding activity. Thus, increased exposure to terrDOM could potentially lead to an increase in bioaccumulation of lipid soluble contaminants in filter feeders. To assess the effect of DOM on bioaccumulation in filter feeders, we exposed the mucous based filter feeding ascidian Ciona intestinalis (formerly known as Ciona intestinalis Type B), to the lipophilic veterinary drug teflubenzuron (log KOW: 5.39) in combination with four DOM treatments: TerrDOM, marDOM, a mix of the two called mixDOM, and seawater without DOM addition. The exposure lasted for 15 days, after which the individuals in all DOM treatments showed a trend towards higher bioaccumulation of Teflubenzuron than those in the seawater control. However, there was considerable overlap in posterior distributions. Against our expectations, marDOM resulted in the highest bioaccumulation factor (BAF), followed by mixDOM, with terrDOM resulting in the lowest BAF except for seawater (kinetic BAF L/kg median, 2.5 %–97.5 % percentile marDOM 94, 74–118; mixDOM 82, 63–104; terrDOM 79; 61-99; seawater 61, 44–79). All BAFs were below the level of concern according to the EU REACH regulation (BAF < 2000 L / kg) and, therefore, likely not environmentally problematic in the examined context. However, the results show that DOM can act as a dietary vector; thus, different combinations of contaminants, DOM, and filter feeding organisms should be tested further.

• Eliassen, Lasse Krøger; Garvang, Even Sletteng; Andersen, Tom; Engseth, Erik; Kristiansen, Kåre Andre & Wiik-Nielsen, Jannicke [Vis alle 7 forfattere av denne artikkelen] (2024). Conspicuous parasite modifies appearance and energetics of a marine copepod. ICES Journal of Marine Science. ISSN 1054-3139. 81(10), s. 2052–2064. doi: 10.1093/icesjms/fsae150. Fulltekst i vitenarkiv Vis sammendrag

  Parasitism is an important driver of ecosystem processes. Copepods are fundamental trophic links in marine food webs and harbour many microeukaryotic parasites, but unreliable access to infected individuals limits quantitative studies of parasite infection costs. Calanus spp., (helgolandicus or finmarchicus), infected with the Yellow-Hyphal Parasite become pigmented and are found near the surface, suggesting predator-mediated dispersal. Conventional markers prevented phylogenetic inference but confirmed that the parasite is not Ichthyophonus hoferi, as previously thought. We identified the pigments, quantified the pigment content and respiration rate, and derived stable isotope signatures of infected and uninfected Calanus spp. to examine costs of infection. We found that the pigments were astaxanthin and β-carotene, associated with the host and parasite, respectively. Parasitized hosts had increased astaxanthin content, reduced respiration rate, and lower lipid content. Ultrastructure imaging revealed parasitic cells associated with lipids in the haemocoel. The changes to host phenotype have detrimental impacts on energetics and the ecology of Calanus. We discuss the role of pigments in parasite-host interactions and suggest that the parasite produces β-carotene pigment for its physiological benefits. The trade-off between physiological benefits of pigments and conspicuousness for parasites is relevant in zooplankton-host systems, as zooplankton rely heavily on transparency for survival.

• Hessen, Dag Olav; Andersen, Tom; McKay, David Armstrong; Kosten, Sarian; Meerhoff, Mariana & Pickard, Amy [Vis alle 7 forfattere av denne artikkelen] (2024). Lake ecosystem tipping points and climate feedbacks. Earth System Dynamics (ESD). ISSN 2190-4979. 15(3), s. 653–669. doi: 10.5194/esd-15-653-2024. Fulltekst i vitenarkiv
• Crapart, Camille Marie; Finstad, Anders Gravbrøt; Hessen, Dag Olav; Vogt, Rolf David & Andersen, Tom (2023). Spatial predictors and temporal forecast of total organic carbon levels in boreal lakes. Science of the Total Environment. ISSN 0048-9697. 870. doi: 10.1016/j.scitotenv.2023.161676. Fulltekst i vitenarkiv Vis sammendrag

  Browning of Fennoscandian boreal lakes is raising concerns for negative ecosystem impacts as well as reduced drinking water quality. Declined sulfur deposition and warmer climate, along with afforestation, other climate impacts and less outfield grazing, have resulted in increased fluxes of Total Organic Carbon (TOC) from catchments to freshwater, and subsequently to coastal waters. This study assesses the major governing factors for increased TOC levels among several catchment characteristics in almost 5000 Fennoscandian lakes and catchments. Normalized Difference Vegetation Index (NDVI), a proxy for plant biomass, and the proportions of peatland in the catchment, along with surface runoff intensity and nitrogen deposition loading, were identified as the main spatial predictors for lake TOC concentrations. A multiple linear model, based on these explanatory variables, was used to simulate future TOC concentration in surface runoff from coastal drainage basins in 2050 and 2100, using the forecasts of climatic variables in two of the Shared Socio-economic Pathways (SSP): 1-2.6 (+2 °C) and 3-7.0 (+4,5 °C). These scenarios yield contrasting effects. SSP 1-2.6 predicts an overall decrease of TOC export to coastal waters, while SSP 3-7.0 in contrast leads to an increase in TOC export.

• Schultze, Sabrina; Andersen, Tom; Knudtzon, Nina; Ruus, Anders; Rundberget, Jan T. & Brooks, Steven J. [Vis alle 9 forfattere av denne artikkelen] (2023). Do DOM quality and origin affect the uptake and accumulation of lipid-soluble contaminants in coastal filter feeders? An experimental simulation of teflubenzuron exposure to blue mussels. Aquatic Toxicology. ISSN 0166-445X. 263. doi: 10.1016/j.aquatox.2023.106696. Fulltekst i vitenarkiv Vis sammendrag

  The increased export of terrestrial dissolved organic matter (terrDOM) to coastal marine ecosystems may affect local filter feeders and the local food web via the altered uptake of organic material and associated contaminants. To compare terrDOM to marine DOM (marDOM) as contaminant vectors to coastal biota, we exposed blue mussels (Mytilus sp.) to the different DOM types in combination with teflubenzuron, a widely applied lipophilic aquaculture medicine targeting salmon lice (Lepeophtheirus salmonis). A 16-day exposure of the blue mussels to DOM and teflubenzuron was followed by a depuration phase of 20 days without teflubenzuron. We calculated teflubenzuron adsorption rates and bioaccumulation factors (BAF) using a Bayesian model, expecting teflubenzuron uptake to be greater with terrDOM than marDOM due to the higher prevalence of large amphipathic humic acids in terrDOM. Humic acids have strong absorption properties and are able to envelope lipophilic molecules. Thus, humic acids can function as an efficient contaminant vector when taken up by filter feeders. Although there were varying degrees of overlap, the mussels tended to accumulate higher amounts of teflubenzuron in the DOM treatments than in the seawater control (bioaccumulation factor [BAF] in seawater: median 106 L/kg; 2.5 %–97.5 % percentile: 69–160 L/kg). Contrary to expectations, mussels exposed to marDOM showed a trend toward more bioaccumulation of teflubenzuron than those exposed to terrDOM (BAF marine 144 L/kg; 102–221 L/kg versus BAF terrestrial: 121 L/kg; 82–186 L/kg). The highest teflubenzuron accumulation was observed with the 50:50 mixture of marDOM and terrDOM (BAF mix: 165 L/kg; 117–244 L/kg). The slight difference in DOM-type accumulation rates observed in this experiment—especially the accumulation rate of terrDOM compared to that of the seawater-only treatment type—was not considered environmentally relevant. Further studies are necessary to see if the observed trends transfer to complex environmental systems.

• Opdal, Anders Martin Frugård; Andersen, Tom; Hessen, Dag Olav; Lindemann, Christian & Aksnes, Dag Lorents (2023). Tracking freshwater browning and coastal water darkening from boreal forests to the Arctic Ocean. Limnology and Oceanography Letters. 8(4), s. 611–619. doi: 10.1002/lol2.10320. Fulltekst i vitenarkiv Vis sammendrag

  The forest cover of Northern Europe has been steadily expanding during the last 120 years. More terrestrial vegetation and carbon fixation leads to more export to surface waters. This may cause freshwater browning, as more degraded plant-litter ends up as chromophoric (colored) dissolved organic matter. Although most freshwater ultimately drains to coastal waters, the link between freshwater browning and coastal water darkening is poorly understood. Here, we explore this relationship through a combination of centennial records of forest cover and coastal water clarity, contemporary optical measurements in lakes and coastal waters, as well as an ocean drift model. We suggest a link between forest cover in Northern Europe and coastal water clarity in the Baltic, Kattegat, and Skagerrak Sea and show how brown-colored freshwater from Northern European catchments can dictate coastal water clarity across thousands of kilometers, from the Baltic lakes to the Barents Sea.

• Heuschele, Jan David; Andersen, Tom; Walseng, Bjørn & Hessen, Dag Olav (2023). Assessing climatic and spatial variables influencing zooplankton richness for space-for-time predictions. Freshwater Biology. ISSN 0046-5070. 69(1), s. 64–73. doi: 10.1111/fwb.14193. Fulltekst i vitenarkiv Vis sammendrag

  1. The macroecological drivers of freshwater diversity are accredited geographical, spatial and climatic variables, but also to productivity, ecosystem age and landscape history. Locally diversity is also influenced by the dispersal ability of species. Here we evaluated how spatial and climatic variables influence species richness and macroecological patterns in Cladocera and Copepoda. We also discuss whether a space-for-time approach is suitable to predict the community's response to the current rapid warming of lakes. 2. We use the presence-absence of pelagic and littoral microcrustaceans in 1465 Norwegian lakes with a wide range of latitudinal, longitudinal, and altitudinal gradients, as well as a wide span in lake areas, to evaluate how spatial and climatic factors influence zooplankton diversity in two major groups: Cladocera and Copepoda. 3. Longitude and latitude per se were poor predictors of zooplankton richness, but a combination of spatial and ecological predictors gave a good spatial prediction of cladoceran and copepod richness. These two groups did, however, not differ in their spatial distribution, with a strikingly fixed proportion of copepods close to 0.3, suggesting no obvious Allee- effects regarding the mode of reproduction (asexual vs sexual). 4. Since temperature alone was a poor predictor of species richness for both groups and dispersal constraints can make it very difficult to estimate a new richness equilibrium under a future climate, space-for-time predictions may have limited value for assessing future patterns of microcrustacean diversity. 5. Based on a quite unique dataset in terms of the sheer number of sites, spatial gradients, and inclusion of littoral species, our study demonstrates that assessments on how changing climate will shape and modulate zooplankton communities in the future are problematic. biogeography, dispersal, diversity, lakes, micro-crustaceans

• Guðmundsson, Guðmundur; Cedhagen, Tomas & Andersen, Tom (2022). Taxonomy and distribution of recent species of the subfamily Nodosariinae (Foraminifera) in Icelandic waters. European Journal of Taxonomy. 824, s. 1–74. doi: 10.5852/ejt.2022.824.1827. Fulltekst i vitenarkiv Vis sammendrag

  Taxonomy of fourteen very little known species of Nodosariinae Ehrenberg, 1838 in Icelandic waters is revised. Knowledge of these species in the North Atlantic relies mainly on studies in the late 19th and early 20th centuries, using large volume samplers. Later studies have emphasized quantitative samples of a few cm3 where the Nodosariinae are very rare. This study analysed 879 dredging samples where Nodosariinae occurred in 492 samples, comprising 7598 specimens of about 415 000 of all picked foraminifera. Ordination analysis of species distributions reflects prominent temperature and salinity differences that exist in the sampling area (753 000 km2) north and south of the Greenland-Scotland Ridge (GSR). Eight species are restricted to southern temperate waters (&gt; 2°C): Dentalina mutabilis (Costa, 1855), Dentalina antarctica Parr, 1950, Dentalina antennula d’Orbigny, 1846, Dentalina filiformis (d’Orbigny, 1826), Grigelis pyrula (d’Orbigny, 1826), Grigelis guttifera (d’Orbigny, 1846) comb. nov., Grigelis semirugosus ? (d’Orbigny, 1846) and Nodosaria subsoluta Cushman, 1923. Four species (Nodosaria haliensis Eiland &amp;#38; Guðmundsson, 2004, Nodosaria incerta Neugeboren, 1856, Dentalina elegans d’Orbigny, 1846 and Dentalina frobisherensis Loeblich &amp;#38; Tappan, 1953) occur mainly north of Iceland. Two species, Dentalina obliqua (Linnaeus,1758) and Pseudonodosaria subannulata (Cushman, 1923), have wide tolerance ranges for physical variables.

• Parra, Nicolas Valiente; Eiler, Alexander; Allesson, Lina; Andersen, Tom; Clayer, Francois & Crapart, Camille Marie [Vis alle 13 forfattere av denne artikkelen] (2022). Catchment properties as predictors of greenhouse gas concentrations across a gradient of boreal lakes. Frontiers in Environmental Science. 10. doi: 10.3389/fenvs.2022.880619. Fulltekst i vitenarkiv Vis sammendrag

  Boreal lakes are the most abundant lakes on Earth. Changes in acid rain deposition, climate, and catchment land use have increased lateral fluxes of terrestrial dissolved organic matter (DOM), resulting in a widespread browning of boreal freshwaters. This browning affects the aqueous communities and ecosystem processes, and boost emissions of the greenhouse gases (GHG) CH 4 , CO 2 , and N 2 O. In this study, we predicted biotic saturation of GHGs in boreal lakes by using a set of chemical, hydrological, climate, and land use parameters. For this purpose, concentrations of GHGs and nutrients (organic C, -P, and -N) were determined in surface water samples from 73 lakes in south-eastern Norway covering wide ranges in DOM and nutrient concentrations, as well as catchment properties and land use. The spatial variation in saturation of each GHG is related to explanatory variables. Catchment characteristics (hydrological and climate parameters) such as lake size and summer precipitation, as well as NDVI, were key determinants when fitting GAM models for CH 4 and CO 2 saturation (explaining 71 and 54%, respectively), while summer precipitation and land use data were the best predictors for the N 2 O saturation, explaining almost 50% of deviance. Our results suggest that lake size, precipitation, and terrestrial primary production in the watershed control the saturation of GHG in boreal lakes. These predictions based on the 73-lake dataset was validated against an independent dataset from 46 lakes in the same region. Together, this provides an improved understanding of drivers and spatial variation in GHG saturation in boreal lakes across wide gradients of lake and catchment properties. The assessment highlights the need to incorporate multiple explanatory parameters in prediction models of GHGs for extrapolation across the boreal biome.

• Heuschele, Jan David; Lode, Torben; Konestabo, Heidi Sjursen; Titelman, Josefin; Andersen, Tom & Borgå, Katrine (2022). Drivers of copper sensitivity in copepods: A meta-analysis of LC50s. Ecotoxicology and Environmental Safety. ISSN 0147-6513. 242. doi: 10.1016/j.ecoenv.2022.113907. Fulltekst i vitenarkiv Vis sammendrag

  Copper is both an essential trace element and a potent pesticide. The use of copper as an antifoulant has increased in the last decades in line with the expanding aquaculture and shipping industries. In aquatic environments, it also affects non-target taxa. One of which are copepods, which constitute the central link in the marine food web. Despite their ecological importance, there are no systematic reviews of the lethal concentration range and drivers of copper toxicity in this taxon. Here, we combined literature data from 31 peer-reviewed articles recording the Lethal Concentration 50 (LC50) for copper in copepods and the experiments' respective environmental, developmental, and taxonomic parameters. The LC50 is a traditional endpoint for toxicity testing used in standardized toxicity testing and many ecological studies. In total, we were able to extract 166 LC50 entries. The variability in the metadata allowed for a general analysis of the drivers of copper sensitivity in copepods. Using a generalized additive modeling approach, we find that temperature increases copper toxicity when above approximately 25 ℃. Counter to our expectations; salinity does not influence copper sensitivity across copepod species. Unsurprisingly, nauplii are more susceptible to copper exposure than adult copepods, and benthos-associated harpacticoids are less sensitive to copper than pelagic calanoids. Our final model can predict sensible specific-specific copper concentrations for future experiments, thus giving an informed analytical approach to range testing in future dose-response experiments. Our model can also potentially improve ecological risk assessment by accounting for environmental differences. The approach can be applied to other toxicants and taxa, which may reveal underlying patterns otherwise obscured by taxonomic and experimental variability.

• Wang, You-Ren; Buchmann, Nina; Hessen, Dag Olav; Stordal, Frode; Erisman, Jan Willem & Vollsnes, Ane Victoria [Vis alle 8 forfattere av denne artikkelen] (2022). Disentangling effects of natural and anthropogenic drivers on forest net ecosystem production. Science of the Total Environment. ISSN 0048-9697. 839. doi: 10.1016/j.scitotenv.2022.156326. Fulltekst i vitenarkiv Vis sammendrag

  Net Ecosystem Production (NEP) of forests is the net carbon dioxide (CO2) fluxes between land and the atmosphere due to forests' biogeochemical processes. NEP varies with natural drivers such as precipitation, air temperature, solar radiation, plant functional type (PFT), and soil texture, which affect the gross primary production and ecosystem respiration, and thus the net C sequestration. It is also known that deposition of sulphur and nitrogen influences NEP in forest ecosystems. These drivers' respective, unique effects on NEP, however, are often difficult to be individually identified by conventional bivariate analysis. Here we show that by analyzing 22 forest sites with 231 site-year data acquired from FLUXNET database across Europe for the years 2000–2014, the individual, unique effects of these drivers on annual forest CO2 fluxes can be disentangled using Generalized Additive Models (GAM) for nonlinear regression analysis. We show that S and N deposition have substantial impacts on NEP, where S deposition above 5 kg S ha−1 yr−1 can significantly reduce NEP, and N deposition around 22 kg N ha−1 yr−1 has the highest positive effect on NEP. Our results suggest that air quality management of S and N is crucial for maintaining healthy biogeochemical functions of forests to mitigate climate change. Furthermore, the empirical models we developed for estimating NEP of forests can serve as a forest management tool in the context of climate change mitigation. Potential applications include the assessment of forest carbon fluxes in the REDD+ framework of the UNFCCC.

• Allesson, Lina; Parra, Nicolas Valiente; Dörsch, Peter; Andersen, Tom; Eiler, Alexander & Hessen, Dag Olav (2022). Drivers and variability of CO2:O2 saturation along a gradient from boreal to Arctic lakes. Scientific Reports. 12. doi: 10.1038/s41598-022-23705-9. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Lakes are significant players for the global climate since they sequester terrestrially derived dissolved organic carbon (DOC), and emit greenhouse gases like CO 2 to the atmosphere. However, the differences in environmental drivers of CO 2 concentrations are not well constrained along latitudinal and thus climate gradients. Our aim here is to provide a better understanding of net heterotrophy and gas balance at the catchment scale in a set of boreal, sub-Arctic and high-Arctic lakes. We assessed water chemistry and concentrations of dissolved O 2 and CO 2 , as well as the CO 2 :O 2 ratio in three groups of lakes separated by steps of approximately 10 degrees latitude in South-Eastern Norway (near 60° N), sub-Arctic lakes in the northernmost part of the Norwegian mainland (near 70° N) and high-Arctic lakes on Svalbard (near 80° N). Across all regions, CO 2 saturation levels varied more (6–1374%) than O 2 saturation levels (85–148%) and hence CO 2 saturation governed the CO 2 :O 2 ratio. The boreal lakes were generally undersaturated with O 2 , while the sub-Arctic and high-Arctic lakes ranged from O 2 saturated to oversaturated. Regardless of location, the majority of the lakes were CO 2 supersaturated. In the boreal lakes the CO 2 :O 2 ratio was mainly related to DOC concentration, in contrast to the sub-Arctic and high-Arctic localities, where conductivity was the major statistical determinant. While the southern part is dominated by granitic and metamorphic bedrock, the sub-Arctic sites are scattered across a range of granitic to sedimentary bed rocks, and the majority of the high-Arctic lakes are situated on limestone, resulting in contrasting lake alkalinities between the regions. DOC dependency of the CO 2 :O 2 ratio in the boreal region together with low alkalinity suggests that in-lake heterotrophic respiration was a major source of lake CO 2 . Contrastingly, the conductivity dependency indicates that CO 2 saturation in the sub-Arctic and high-Arctic lakes was to a large part explained by DIC input from catchment respiration and carbonate weathering.

• Schultze, Sabrina; Andersen, Tom; Hessen, Dag Olav; Ruus, Anders; Borgå, Katrine & Poste, Amanda (2022). Land-cover, climate and fjord morphology drive differences in organic matter and nutrient dynamics in two contrasting northern river-fjord systems. Estuarine, Coastal and Shelf Science. ISSN 0272-7714. 270. doi: 10.1016/j.ecss.2022.107831. Fulltekst i vitenarkiv Vis sammendrag

  Climate and land-use changes are leading to impacts on individual ecosystems as well as shifts in transfer dynamics between interconnected systems. At the land-ocean interface, changes in riverine inputs of organic matter (OM) and nutrients have the potential to lead to shifts in coastal carbon and nutrient cycling with consequences for ecosystem structure and function. In this study, we assess OM and nutrient dynamics for two contrasting Norwegian river-to-fjord systems: a boreal system with a forested catchment draining into a narrow fjord (‘narrow boreal system’), and a subarctic system where lowland forests and mountainous regions drain into a broad fjord (‘broad subarctic system’). We characterized seasonal organic carbon and nutrient concentrations and DOM absorption properties for samples collected along transects from river to outer fjord during 2015/2016. While differences in catchment properties drove contrasts in river chemistry between the two study rivers, fjord morphology and hydrodynamics as well as dissolved organic carbon (DOC) and nutrient concentrations in marine receiving waters predicted water-chemistry patterns along the transect. The narrow boreal system, with high riverine DOC and nutrient concentrations, was structured mainly by a horizontal salinity gradient from river to outer fjord, with limited impact of seasonality. In contrast, the broad subarctic system tended to be dominated by vertical salinity stratification, with strong between-date differences in surface water salinity linked to seasonality in river discharge. These dynamics were also reflected in the strong horizontal gradients in DOC, nutrients and DOM properties in the narrow boreal system, in contrast to the broad subarctic system, where strong seasonality paired with a lack of strong contrast between riverine and marine concentrations of DOC and most nutrients led to an uncoupling between salinity and other water chemistry variables. In the narrow boreal system, terrestrial OM dominated both the particulate and dissolved OM pools, while OM in the broad subarctic system was derived primarily from marine phytoplankton. Non-linear declines in NO3 + NO2 were observed consistently in the boreal system and during the productive spring season in the subarctic system, suggesting biological uptake and a potentially important role of these rivers as sources of bioavailable N to coastal ecosystems. The results from these two case studies highlight the complex and interacting effects of catchment land-cover, river water chemistry and discharge, fjord morphometry and hydrodynamics in structuring the transport, fate and potential impacts of terrestrially-derived nutrients and organic matter in northern coastal environments.

• Su, Ming; Zhu, Yiping; Andersen, Tom; Wang, Xianyun; Yu, Zhiyong & Lu, Jinping [Vis alle 11 forfattere av denne artikkelen] (2022). Light-dominated selection shaping filamentous cyanobacterial assemblages drives odor problem in a drinking water reservoir. npj Clean Water. 5(1). doi: 10.1038/s41545-022-00181-2. Fulltekst i vitenarkiv Vis sammendrag

  Filamentous cyanobacteria have substantial niche overlap, and the causal mechanism behind their succession remains unclear. This has practical significance since several filamentous genera are the main producers of the musty odorant 2-methylisoborneol (MIB), which lead to odor problems in drinking water. This study investigates the relationships between two filamentous cyanobacteria, the MIB-producing genus Planktothrix and the non-MIB-producing genus Pseudanabaena, in a drinking water reservoir. We firstly identified their niche characteristics based on a monitoring dataset, combined this information with culture experiments and developed a niche-based model to clarify these processes. The results reveal that the optimal light requirements of Pseudanabaena (1.56 mol m−2 d−1) are lower than those of Planktothrix (3.67 mol m−2 d−1); their light niche differentiation led to a fundamental replacement of Planktothrix (2013) by Pseudanabaena (2015) along with MIB decreases in this reservoir during 2013 and 2015. This study suggests that light is a major driving force responsible for the succession between filamentous cyanobacteria, and that subtle niche differentiation may play an important role in shaping the filamentous cyanobacterial assemblages that drives the MIB odor problems in drinking water reservoirs.

• Rusch, Johannes; Strand, David; Laurendz, Charlotte; Andersen, Tom; Johnsen, Stein Ivar & Edsman, Lennart [Vis alle 7 forfattere av denne artikkelen] (2022). Exploring the eDNA dynamics of the host-pathogen pair Pacifastacus leniusculus (Decapoda) and Aphanomyces astaci (Saprolegniales) under experimental conditions. NeoBiota. ISSN 1619-0033. 79, s. 1–29. doi: 10.3897/NEOBIOTA.79.82793. Fulltekst i vitenarkiv Vis sammendrag

  The oomycete Aphanomyces astaci causes crayfish plague, a disease threatening native European crayfish. It is carried and transmitted by American crayfish species, which are the original hosts of A. astaci. In recent years, environmental DNA (eDNA) methods have been successfully implemented to monitor the spread of both A. astaci and its hosts. However, still little is known about how population density and other en vironmental factors influence the detectability of this host-pathogen complex. In a mesocosm experiment, we tested the influence of crayfish density, temperature and food availability on the detectability of eDNA for A. astaci and its host, signal crayfish Pacifastacus leniusculus. We also compared eDNA results with crayfish population density measured by catch per unit effort (CPUE) from two lakes with varying crayfish density and A. astaci prevalence. The mesocosm experiment revealed that a limited set of controlled factors can substantially change the detectable amount of eDNA, even though the physical presence of the target organisms remains the same. In cold, clear water, eDNA quantities of both targets increased far more than in a linear fashion with increased crayfish density. However, the presence of food decreased the detectability of crayfish eDNA, presumably through increased microbial-induced eDNA degradation. For A. astaci, where eDNA typically represents living spores, food did not affect the detectability. However, high water temperature strongly reduced it. The increased complexity and variability of factors influenc ing eDNA concentration under natural conditions, compared to a controlled experimental environment, suggests that establishing a reliable relationship between eDNA quantities and crayfish density is difficult to achieve. This was also supported by field data, where we found minimal correspondence between eDNA quantity and CPUE data. A comparison between quantitative real-time PCR (qPCR) analysis and droplet-digital PCR (ddPCR) analysis revealed higher detection success of the targets in field samples when using qPCR. Overall, our results support eDNA as an effective tool for presence-absence monitor ing, but it seems less suited for biomass quantification and population density estimates. Detection of A. astaci and P. leniusculus is not influenced uniformly by respective environmental factors. Consequently, we recommend a strategy of monitoring both targets, where the detection of one may point towards the presence of the other.

• Fontaine, Laurent; Khomich, Maryia; Andersen, Tom; Hessen, Dag Olav; Rasconi, Serena & Davey, Marie Louise [Vis alle 7 forfattere av denne artikkelen] (2021). Multiple thresholds and trajectories of microbial biodiversity predicted across browning gradients by neural networks and decision tree learning. ISME Communications. 1. doi: 10.1038/s43705-021-00038-8. Fulltekst i vitenarkiv Vis sammendrag

  Ecological association studies often assume monotonicity such as between biodiversity and environmental properties although there is growing evidence that nonmonotonic relations dominate in nature. Here, we apply machine-learning algorithms to reveal the nonmonotonic association between microbial diversity and an anthropogenic-induced large-scale change, the browning of freshwaters, along a longitudinal gradient covering 70 boreal lakes in Scandinavia. Measures of bacterial richness and evenness (alpha-diversity) showed nonmonotonic trends in relation to environmental gradients, peaking at intermediate levels of browning. Depending on the statistical methods, variables indicative for browning could explain 5% of the variance in bacterial community composition (beta-diversity) when applying standard methods assuming monotonic relations and up to 45% with machine- learning methods taking non-monotonicity into account. This non-monotonicity observed at the community level was explained by the complex interchangeable nature of individual taxa responses as shown by a high degree of nonmonotonic responses of individual bacterial sequence variants to browning. Furthermore, the nonmonotonic models provide the position of thresholds and predict alternative bacterial diversity trajectories in boreal freshwater as a result of ongoing climate and land-use changes, which in turn will affect entire ecosystem metabolism and likely greenhouse gas production.

• Crapart, Camille Marie; Andersen, Tom; Hessen, Dag Olav; Parra, Nicolas Valiente & Vogt, Rolf David (2021). Factors Governing Biodegradability of Dissolved Natural Organic Matter in Lake Water. Water. 13(16). doi: 10.3390/w13162210. Fulltekst i vitenarkiv Vis sammendrag

  Dissolved Natural Organic Matter (DNOM) is a heterogeneous mixture of partly degraded, oxidised and resynthesised organic compounds of terrestrial or aquatic origin. In the boreal biome, it plays a central role in element cycling and practically all biogeochemical processes governing the physico-chemistry of surface waters. Because it plays a central role in multiple aquatic processes, especially microbial respiration, an improved understanding of the biodegradability of the DNOM in surface water is needed. Here the current study, we used a relatively cheap and non-laborious analytical method to determine the biodegradability of DNOM, based on the rate and the time lapse at which it is decomposed. This was achieved by monitoring the rate of oxygen consumption during incubation with addition of nutrients. A synoptic method study, using a set of lake water samples from southeast Norway, showed that the maximum respiration rate (RR) and the normalised RR (respiration rate per unit of carbon) of the DNOM in the lakes varied significantly. This RR is conceived as a proxy for the biodegradability of the DNOM. The sUVa of the DNOM and the C:N ratio were the main predictors of the RR. This implies that the biodegradability of DNOM in these predominantly oligotrophic and dystrophic lake waters was mainly governed by their molecular size and aromaticity, in addition to its C:N ratio in the same manner as found for soil organic matter. The normalised RR (independently of the overall concentration of DOC) was predicted by the molecular weight and by the origin of the organic matter. The duration of the first phase of rapid biodegradation of the DNOM (BdgT) was found to be higher in lakes with a mixture of autochthonous and allochthonous DNOM, in addition to the amount of biodegradable DNOM.

• Gundersen, Madeleine S.; Vadstein, Olav; Bakke, Ingrid; Andersen, Tom & Morelan, Ian (2021). The effect of periodic disturbances and carrying capacity on the significance of selection and drift in complex bacterial communities. ISME Communications. doi: 10.1038/s43705-021-00058-4. Fulltekst i vitenarkiv Vis sammendrag

  Understanding how periodical disturbances affect the community assembly processes is vital for predicting temporal dynamics in microbial communities. However, the effect of dilutions as disturbances are poorly understood. We used a marine bacterial community to investigate the effect of disturbance (+/−) and carrying capacity (high/low) over 50 days in a dispersal-limited 2 × 2 factorial study in triplicates, with a crossover in the disturbance regime between microcosms halfway in the experiment. We modelled the rate of change in community composition between replicates and used this rate to quantify selection and ecological drift. The disturbed communities increased in Bray–Curtis similarity with 0.011 ± 0.0045 (Period 1) and 0.0092 ± 0.0080 day−1 (Period 2), indicating that selection dominated community assembly. The undisturbed communities decreased in similarity at a rate of −0.015 ± 0.0038 day−1 in Period 1 and were stable in Period 2 at 0.00050 ± 0.0040 day−1, suggesting drift structured community assembly. Interestingly, carrying capacity had minor effects on community dynamics. This study is the first to show that stochastic effects are suppressed by periodical disturbances resulting in exponential growth periods due to density-independent biomass loss and resource input. The increased contribution of selection as a response to disturbances implies that ecosystem prediction is achievable.

• Lode, Torben; Heuschele, Jan David; Andersen, Tom; Titelman, Josefin; Hylland, Ketil & Borgå, Katrine (2021). Density-Dependent Metabolic Costs of Copper Exposure in a Coastal Copepod. Environmental Toxicology and Chemistry. ISSN 0730-7268. 40(9), s. 2538–2546. doi: 10.1002/etc.5141. Fulltekst i vitenarkiv Vis sammendrag

  Traditional ecotoxicology methods involving copepods have focused on exposure of pooled individuals and averaged responses, but there is increasing awareness of the importance of individual variation. Many biological traits are density dependent, and decisions to use single-individual or pooled exposure may affect responses to anthropogenic stressors. We investigated how conspecific density as a biotic stressor affects behavioral and respiratory responses to copper (Cu) exposure in the coastal copepod Tigriopus brevicornis. Adults were incubated at densities of 1, 2, or 4 individuals per replicate in 3.2 mL of exposure medium (23 µg Cu L–1 or control). Our results show an interaction of Cu exposure and density on respiration. The Cu exposure increased respiration, but this effect diminished with increasing density. We also found reduced swimming activity with increasing density. We propose 2 nonexclusive alternative explanations for the density-dependent respiratory increase of Cu exposure: 1) a behavioral stress response to low conspecific density, or 2) increased Cu exposure due to increased swimming activity. We emphasize the importance of considering density-dependency in responses when designing and interpreting ecotoxicology studies.

• Ringvold, Halldis; Guðmundsson, G. & Andersen, Tom (2021). Starfish (Asteroidea, Echinodermata) from Iceland; spatial distribution and abundance. Deep Sea Research Part I: Oceanographic Research Papers. ISSN 0967-0637. 176, s. 1–15. doi: 10.1016/j.dsr.2021.103605. Fulltekst i vitenarkiv Vis sammendrag

  The Benthic Invertebrates of Icelandic Waters programme (BIOICE) was conducted between 1991 and 2004, for the purpose of gathering specimens within the Icelandic Exclusive Economic Zone (59° 58′N – 69° 35‘N and 30° 52’W – 5° 34′W). In total 12961 asteroid specimens were collected from 654 sampling stations, which comprises 63% of all sampling stations. Sampling depths were between 20 and 2700 m. Total recorded asteroids for Iceland now include 64 species from 21 families and 45 genera, including 23 new species added from this study. The most abundant asteroids collected by BIOICE were Pontaster tenuispinus, Bathybiaster vexillifer and Henricia pertusa group. Maximum species richness was found at depths 100–200 m and 400–500 m, located above the cold Norwegian Sea Deep Water (−1 °C). 24 of the species were recorded at an abundance-weighted mean depth below 1300 m. The area south of the Greenland-Scotland Ridge (GS-Ridge) was more species rich than north of the ridge. Specimens within the rare Myxasteridae family were recorded. A nonmetric multidimensional scaling (NMDS) converged fast from multiple starting points with stress = 0.18. All five abiotic factors (depth, temperature, salinity, latitude and longitude) were strongly related to two of the NMDS ordination axis. The first ordination axis scores had strongest correlation with depth (r = 0.84), whereas the second ordination axis scores had strongest correlation with latitude (r = 0.71).

• Volpe, Charlotte; Vadstein, Olav; Andersen, Geir & Andersen, Tom (2021). Nanocosm: A well plate photobioreactor for environmental and biotechnological studies. Lab on a Chip. ISSN 1473-0197. 21(10), s. 2027–2039. doi: 10.1039/d0lc01250e. Fulltekst i vitenarkiv Vis sammendrag

  Phytoplankton are key primary producers at the bottom of the aquatic food chain. They are a highly diverse group of organisms essential for the functioning of our ecosystems and because of their characteristics, their biomass is considered for various commercial applications. A full appreciation of their abundance, diversity and potential is only feasible by using systems that enable simultaneous testing of strains and/or variables in a fast and easy way. A major bottleneck is the lack of a cost-effective method with the capacity for complex experimental set-ups that enable fast and reproducible screening and analysis. In this study, we present nanocosm, a versatile LED-based micro-scale photobioreactor (PBR) that allows simultaneous testing of multiple variables such as temperature and light within the same plate. Every well can be independently controlled for intensity, temporal variation and light type (RGB, white, UV). We show that our systems guarantee homogeneous conditions because of controlled temperature and evaporation and adjustments for light crosstalk. By ensuring controlled environmental conditions the nanocosm is suitable for running factorial experimental designs where each well can be used as an independent micro-PBR. To validate culture performances, we assess well-to-well reproducibility and our results show minimal well-to-well variability for all the conditions tested. Possible modes of operation and application are discussed together with future development of the system.

• Lode, Torben; Heuschele, Jan David; Andersen, Tom; Titelman, Josefin; Hylland, Ketil & Borgå, Katrine (2020). Contrasting Effects of Predation Risk and Copper on Copepod Respiration Rates. Environmental Toxicology and Chemistry. ISSN 0730-7268. 39(9), s. 1765–1773. doi: 10.1002/etc.4804. Fulltekst i vitenarkiv Vis sammendrag

  Natural biotic and anthropogenic stressors can interact to alter contaminant toxicity. Energetic restrictions are potential mechanisms causing this pattern. To identify processes underlying observed effects of predation risk and copper (Cu) on delayed copepod age at maturity, we examined how these 2 stressors affect respiration rates. We tested 2 very different copepod species: the large, pelagic calanoid Calanus finmarchicus and the small, semibenthic harpacticoid Tigriopus brevicornis. Adult individuals were exposed for 12 h to the treatments: predation risk, Cu (23 µg L−1), combined predation risk and Cu (23 µg L−1), or control. Oxygen concentrations were monitored continuously. The 2 species differed in their responses. We found no clear effects of either stressor in C. finmarchicus. In T. brevicornis, predation risk increased respiration rates, whereas Cu alone had little impact. In contrast, combined exposure to predation risk and Cu interacted to reduce respiration rates to less than expected. We further observed an effect of sex because female‐biased T. brevicornis replicates were more sensitive to both predation risk (increased respiration rates) and Cu exposure (reduced respiration rates). The present study provides further evidence that predation risk can interact with copepod responses toward Cu exposure. Interactive effects of biotic stressors ought to be considered to improve future marine environmental monitoring. Environ Toxicol Chem 2020;39:1765–1773. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

• Ershova, Victoria; Prokopiev, Andrei; Khudoley, Andrey; Andersen, Tom; Kullerud, Kåre & Kolchanov, Daniil (2020). U–Pb Age and Hf Isotope Geochemistry of Detrital Zircons from Cambrian Sandstones of the Severnaya Zemlya Archipelago and Northern Taimyr (Russian High Arctic). Minerals. 10(1). doi: 10.3390/min10010036. Fulltekst i vitenarkiv Vis sammendrag

  U–Pb and Lu–Hf isotope analyses of detrital zircons collected from metasedimentary rocks from the southern part of Kara Terrane (northern Taimyr and Severnaya Zemlya archipelago) provide vital information about the paleogeographic and tectonic evolution of the Russian High Arctic. The detrital zircon signatures of the seven dated samples are very similar, suggesting a common provenance for the clastic detritus. The majority of the dated grains belong to the late Neoproterozoic to Cambrian ages, which suggests the maximum depositional age of the enclosing sedimentary units to be Cambrian. The εHf(t) values indicate that juvenile magma mixed with evolved continental crust and the zircons crystallized within a continental magmatic arc setting. Our data strongly suggest that the main provenance for the studied clastics was located within the Timanian Orogen. A review of the available detrital zircon ages from late Neoproterozoic to Cambrian strata across the wider Arctic strongly suggests that Kara Terrane, Novaya Zemlya, Seward Peninsula (Arctic Alaska), Alexander Terrane, De Long Islands, and Scandinavian Caledonides all formed a single tectonic domain during the Cambrian age, with clastics predominantly sourced from the Timanian Orogen.

• Allesson, Lina; Koehler, Birgit; Thrane, Jan-Erik; Andersen, Tom & Hessen, Dag O (2020). The role of photomineralization for CO2 emissions in boreal lakes along a gradient of dissolved organic matter. Limnology and Oceanography. ISSN 0024-3590. 66(1), s. 158–170. doi: 10.1002/lno.11594. Fulltekst i vitenarkiv Vis sammendrag

  Many boreal lakes are experiencing an increase in concentrations of terrestrially derived dissolved organic matter (DOM)—a process commonly labeled “browning.” Browning affects microbial and photochemical mineralization of DOM, and causes increased light attenuation and hence reduced photosynthesis. Consequently, browning regulates lake heterotrophy and net CO2‐efflux to the atmosphere. Climate and environmental change makes ecological forecasting and global carbon cycle modeling increasingly important. A proper understanding of the magnitude and relative contribution from CO2‐generating processes for lakes ranging in dissolve organic carbon (DOC) concentrations is therefore crucial for constraining models and forecasts. Here, we aim to study the relative contribution of photomineralization to total CO2 production in 70 Scandinavian lakes along an ecosystem gradient of DOC concentration. We combined spectral data from the lakes with regression estimates between optical parameters and wavelength specific photochemical reactivity to estimate rates of photochemical DOC mineralization. Further, we estimated total in‐lake CO2‐production and efflux from lake chemical and physical data. Photochemical mineralization corresponded on average to 9% ± 1% of the total CO2‐evasion, with the highest contribution in clear lakes. The calculated relative contribution of photochemical mineralization to total in‐lake CO2‐production was about 3% ± 0.2% in all lakes. Although lakes differed substantially in color, depth‐integrated photomineralization estimates were similar in all lakes, regardless of DOC concentrations. DOC concentrations were positively related to CO2‐efflux and total in‐lake CO2‐production but negatively related to primary production. We conclude that enhanced rates of photochemical mineralization will be a minor contributor to increased heterotrophy under increased browning.

• Allesson, Lina; Andersen, Tom; Dörsch, Peter; Eiler, Alexander; Wei, Jing & Hessen, Dag Olav (2020). Phosphorus availability promotes bacterial DOC-mineralization, but not cumulative CO2-production. Frontiers in Microbiology. 11. doi: 10.3389/fmicb.2020.569879. Fulltekst i vitenarkiv Vis sammendrag

  The current trend of increasing input of terrestrially derived dissolved organic carbon (DOC) to boreal freshwater systems is causing increased levels of carbon dioxide (CO 2 ) supersaturation and degassing. Phosphorus (P) is often the most limiting nutrient for bacterial growth and would thus be expected to increase overall mineralization rates and CO 2 production. However, high carbon (C) to P ratios of terrestrially derived DOC could also cause elevated cell-specific respiration of the excess C in heterotrophic bacteria. Using data from a survey of 75 Scandinavian lakes along an ecosystem gradient of DOC, we estimated in situ CO 2 production rates. These rates showed a unimodal response with DOC-specific CO 2 production negatively related to DOC:total phosphorus (TP) ratio, and a turning point at 5 mg C L −1 , indicating higher DOC turnover rates in productive than in unproductive lakes. To further assess the dependency of bacterial respiration (BR) on DOC and P, we monitored CO 2 production in incubations of water with a gradient of DOC crossed with two levels of inorganic P. Finally, we crossed DOC and P with a temperature gradient to test the temperature dependency of respiration rates [as oxygen (O 2 ) consumption]. While total CO 2 production seemed to be unaffected by P additions, respiration rates, and growth yields, as estimated by ribosomal gene copy numbers, suggest increased bacterial growth and decreased cell-specific respiration under non-limited P conditions. Respiration rates showed a sigmoid response to increasing DOC availability reaching a plateau at about 20 mg C L −1 of initial DOC concentrations. In addition to these P and DOC level effects, respiration rates responded in a non-monotonic fashion to temperature with an increase in respiration rates by a factor of 2.6 (±0.2) from 15 to 25°C and a decrease above 30°C. The combined results from the survey and experiments highlight DOC as the major determinant of CO 2 production in boreal lakes, with P and temperature as significant modulators of respiration kinetics.

• Sunde, Øyvind; Friis, Henrik; Andersen, Tom; Trumbull, Robert; Wiedenbeck, Michael & Lyckberg, Peter [Vis alle 9 forfattere av denne artikkelen] (2020). Boron isotope composition of coexisting tourmaline and hambergite in alkaline and granitic pegmatites. Lithos. ISSN 0024-4937. 352-353. doi: 10.1016/j.lithos.2019.105293. Fulltekst i vitenarkiv Vis sammendrag

  The boron isotopic composition of tourmaline and hambergite (Be2BO3[OH,F]) from peraluminous (n = 12), peralkaline (n = 1), and peralkaline nepheline syenite (n = 16) pegmatites has been measured by secondary ion mass spectrometry, for which a new hambergite reference material was developed. The focus of this study is on nepheline syenite pegmatites from the Larvik Plutonic Complex (Norway) and one peralkaline pegmatite related to the nearby Eikeren-Skrim Complex (Norway), where we investigate the source of boron as being from magmatic vs. external fluids. Tourmaline-hambergite mineral pairs were also analysed from peraluminous pegmatite localities (Russia, Tajikistan, and Pakistan) to test for systematic B-isotope fractionation between these two minerals. Tourmaline and hambergite from peraluminous granitic pegmatites have light boron ratios (δ11B = −12.9to −1.0‰) associated with S-type granites, whereas peralkaline granitic and nepheline syenite pegmatites have boron ratios (δ11B = −1.7 to 11.8‰), which we interpret is a result of heavy‑boron enrichment from external fluids. Our data show that hambergite tracks isotope variations of its geochemical setting and could therefore be used as a proxy mineral in place of tourmaline when geochemical stability favours hambergite. The results suggest a slight but consistent partitioning of B-isotopes between tourmaline and hambergite, with Δ11B = δ11Btourmaline−δ11Bhambergite in the range of approximately −3‰ to −5‰. Boron is in trigonal coordination with oxygen in both of these mineral phases as verified by NMR. Single crystal XRD analyses of tourmaline and hambergite reveal consistent longer <B-O > distances of tourmaline relative to hambergite. We attribute the boron isotopic fractionation to the longer <B-O > bond-lengths in tourmaline compared with hambergite.

• Andersen, Tom; Hessen, Dag Olav; Håll, Johnny Peter; Khomich, Maryia; Kyle, Marcia & Lindholm, Markus [Vis alle 10 forfattere av denne artikkelen] (2020). Congruence, but no cascade—Pelagic biodiversity across three trophic levels in Nordic lakes. Ecology and Evolution. 10(15), s. 8153–8165. doi: 10.1002/ece3.6514. Fulltekst i vitenarkiv Vis sammendrag

  Covariation in species richness and community structure across taxonomical groups (cross‐taxon congruence) has practical consequences for the identification of biodiversity surrogates and proxies, as well as theoretical ramifications for understanding the mechanisms maintaining and sustaining biodiversity. We found there to exist a high cross‐taxon congruence between phytoplankton, zooplankton, and fish in 73 large Scandinavian lakes across a 750 km longitudinal transect. The fraction of the total diversity variation explained by local environment alone was small for all trophic levels while a substantial fraction could be explained by spatial gradient variables. Almost half of the explained variation could not be resolved between local and spatial factors, possibly due to confounding issues between longitude and landscape productivity. There is strong consensus that the longitudinal gradient found in the regional fish community results from postglacial dispersal limitations, while there is much less evidence for the species richness and community structure gradients at lower trophic levels being directly affected by dispersal limitation over the same time scale. We found strong support for bidirectional interactions between fish and zooplankton species richness, while corresponding interactions between phytoplankton and zooplankton richness were much weaker. Both the weakening of the linkage at lower trophic levels and the bidirectional nature of the interaction indicates that the underlying mechanism must be qualitatively different from a trophic cascade.

• Heuschele, Jan David; Lode, Torben; Andersen, Tom & Titelman, Josefin (2020). The Hidden Dimension: Context‐Dependent Expression of Repeatable Behavior in Copepods. Environmental Toxicology and Chemistry. ISSN 0730-7268. 39(5), s. 1017–1026. doi: 10.1002/etc.4688. Fulltekst i vitenarkiv Vis sammendrag

  In ecotoxicology and aquatic ecology, we often ignore responses of individuals and focus on average responses. However, both terrestrial and aquatic animals display consistent behavioral differences between individuals. The distribution of behavioral differences within a population contains vital information for predicting population responses to novel environmental challenges. Currently, individual data for behavioral and physiological traits of small marine invertebrates are few, partly because such variation is lost within published group means and assumed normality. We tested the combined effects of an inorganic contaminant (copper) and a biological stressor (i.e., chemical cues of a fish predator) on activity in a marine copepod. Although direct stress effects were weak, individuals behaved consistently differently, depending on the context. Individual differences in behavior were only expressed under the influence of kairomones, but not by copper exposure alone. This finding indicates that copepods express repeatable and context‐dependent behavior. We also demonstrate how large variations in behavioral data can hide consistent differences between individuals. Environ Toxicol Chem 2020;39:1017–1026. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

• Karsli, Orhan; Caran, Şemsettin; Çoban, Hakan; Şengün, Fırat; Tekkanat, Osman & Andersen, Tom (2020). Melting of the juvenile lower crust in a far-field response to roll-back of the southern Neotethyan oceanic lithosphere: the Oligocene adakitic dacites, NE Turkey. Lithos. ISSN 0024-4937. 370-371. doi: 10.1016/j.lithos.2020.105614. Fulltekst i vitenarkiv
• Eshun-Wilson, Franceen; Wolf, Raoul; Andersen, Tom; Hessen, Dag O & Sperfeld, Erik (2020). UV radiation affects antipredatory defense traits in Daphnia pulex. Ecology and Evolution. 10(24), s. 14082–14097. doi: 10.1002/ece3.6999. Fulltekst i vitenarkiv Vis sammendrag

  In aquatic environments, prey perceive predator threats by chemical cues called kairomones, which can induce changes in their morphology, life histories, and behavior. Predator‐induced defenses have allowed for prey, such as Daphnia pulex, to avert capture by common invertebrate predators, such as Chaoborus sp. larvae. However, the influence of additional stressors, such as ultraviolet radiation (UVR), on the Daphnia–Chaoborus interaction is not settled as UVR may for instance deactivate the kairomone. In laboratory experiments, we investigated the combined effect of kairomones and UVR at ecologically relevant levels on induced morphological defenses of two D. pulex clones. We found that kairomones were not deactivated by UVR exposure. Instead, UVR exposure suppressed induced morphological defense traits of D. pulex juveniles under predation threat by generally decreasing the number of neckteeth and especially by decreasing the size of the pedestal beneath the neckteeth. UVR exposure also decreased the body length, body width, and tail spine length of juveniles, likely additionally increasing the vulnerability to Chaoborus predation. Our results suggest potential detrimental effects on fitness and survival of D. pulex subject to UVR stress, with consequences on community composition and food web structure in clear and shallow water bodies.

• Heuschele, Jan David; Lode, Torben; Andersen, Tom; Borgå, Katrine & Titelman, Josefin (2019). An affordable and automated imaging approach to acquire highly resolved individual data—an example of copepod growth in response to multiple stressors. PeerJ. 7, s. 1–22. doi: 10.7717/peerj.6776. Fulltekst i vitenarkiv Vis sammendrag

  Individual trait variation is essential for populations to cope with multiple stressors and continuously changing environments. The immense number of possible stressor combinations and the influence of phenotypic variation makes experimental testing for effects on organisms challenging. The acquisition of such data requires many replicates and is notoriously laborious. It is further complicated when responses occur over short time periods. To overcome such challenges, we developed an automated imaging platform to acquire temporally highly resolved individual data. We tested this platform by exposing copepods to a combination of a biotic stressor (predator cues) and a toxicant (copper) and measured the growth response of individual copepods. We tested the automatically acquired data against published manually acquired data with much lower temporal resolution. We find the same general potentiating effects of predator cues on the adverse effects of copper, and the influence of an individual’s clutch identity on its ability to resist stress, between the data obtained from low and high temporal resolution. However, when using the high temporal resolution, we also uncovered effects of clutch ID on the timing and duration of stage transitions, which highlights the importance of considering phenotypic variation in ecotoxicological testing. Phenotypic variation is usually not acknowledged in ecotoxicological testing. Our approach is scalable, affordable, and adjustable to accommodate both aquatic and terrestrial organisms, and a wide range of visually detectable endpoints. We discuss future extensions that would further widen its applicability.

• Hagman, Camilla Hedlund Corneliussen; Skjelbred, Birger; Thrane, Jan-Erik; Andersen, Tom & Wit, Heleen A de (2019). Growth responses of the nuisance algae Gonyostomum semen (Raphidophyceae) to DOC and associated alterations of light quality and quantity. Aquatic Microbial Ecology. ISSN 0948-3055. 82(3), s. 241–251. doi: 10.3354/ame01894. Fulltekst i vitenarkiv Vis sammendrag

  In recent decades, the freshwater alga Gonyostomum semen (Ehrenberg) Diesing has increased in abundance and distribution, which has created problems regarding the use of lakes for drinking water and recreation. Increases in lake dissolved organic carbon (DOC; browning) and climate warming are among current hypotheses that explain the phenomenon of increased abundance of G. semen. A replicated, multifactorial laboratory experiment was performed in order to test the effects of DOC and light quality and irradiance on growth of G. semen in 96-well plates. Each well had a separate light source, creating a gradient of irradiance (10-140 µmol photons m-2 s-1) and wavelength (white, red, green and blue), combined with a DOC gradient (0-50 mg C l-1), all within representative ranges for the summer epilimnion in boreal waters. The experiment showed that growth of G. semen was significantly enhanced by the addition of DOC. No growth response relating to wavelengths was found, but where irradiance was inhibitory, a shading effect from DOC was evident. A composed response to increases in DOC suggests a versatility of G. semen that gives it a competitive advantage over other phytoplankton in humic lake ecosystems. Hence, further increases in abundance and bloom frequency of G. semen as browning continues in boreal lakes are to be expected.

• Su, Ming; Andersen, Tom; Burch, Michael; Jia, Zeyu; An, Wei & Yu, Jianwei [Vis alle 7 forfattere av denne artikkelen] (2019). Succession and interaction of surface and subsurface cyanobacterial blooms in oligotrophic/mesotrophic reservoirs: A case study in Miyun Reservoir. Science of the Total Environment. ISSN 0048-9697. 649, s. 1553–1562. doi: 10.1016/j.scitotenv.2018.08.307. Fulltekst i vitenarkiv Vis sammendrag

  Subsurface cyanobacterial blooms, are a significant source of odor problems in source water and have been recorded in many oligotrophic/mesotrophic drinking water reservoirs. In this study, we explored the key driving forces responsible for the succession between surface and subsurface cyanobacteria using ecological niche modelling based upon a case study in Miyun Reservoir, China. The results suggest a negative effect of water depth and surface light irradiance (I0) on subsurface Planktothrix sp. growth (p-values < 0.001), and a unimodal effect of surface water temperature (T0) with the optimum at 23 °C (p-value < 0.001). While the surface Microcystis spp. shows a strong positive relationship with temperature (T0; p-value < 0.001), and significant effects for the interaction between T0 and I0 (p- value < 0.01). In addition, we identified the extent and type of interaction between subsurface and surface cyanobacteria and conclude that the high irradiance surface water combined with sufficient nutrients at the pre-bloom stage are key factors responsible for the preferential growth of surface cyanobacteria, while the gradual decline of the surface cyanobacteria in post-bloom stage is associated with nutrient reduction. This decline and loss of surface populations enhanced underwater irradiance and thus promoted the growth and allowed for succession of subsurface cyanobacteria in deeper layers where the nutrient supply was still adequate. Based upon this, the growth potentials for the subsurface and surface cyanobacteria are different under different environmental conditions: the subsurface cyanobacteria have greater growth potential than surface cyanobacteria in shallow oligotrophic and deep eutrophic reservoirs during median light irrigation seasons.

• Hitchcock, Daniel James; Andersen, Tom; Varpe, Øystein; Loonen, Maarten; Warner, Nicholas Alexander & Herzke, Dorte [Vis alle 10 forfattere av denne artikkelen] (2019). Potential Effect of Migration Strategy on Pollutant Occurrence in Eggs of Arctic Breeding Barnacle Geese (Branta leucopsis). Environmental Science and Technology. ISSN 0013-936X. 53(9), s. 5427–5435. doi: 10.1021/acs.est.9b00014. Fulltekst i vitenarkiv Vis sammendrag

  Arctic-breeding geese acquire resources for egg production from overwintering and breeding grounds, where pollutant exposure may differ. We investigated the effect of migration strategy on pollutant occurrence of lipophilic polychlorinated biphenyls (PCBs) and protein-associated poly- and perfluoroalkyl substances (PFASs) and mercury (Hg) in eggs of herbivorous barnacle geese (Branta leucopsis) from an island colony on Svalbard. Stable isotopes (δ13C and δ15N) in eggs and vegetation collected along the migration route were similar. Pollutant concentrations in eggs were low, reflecting their terrestrial diet (∑PCB = 1.23 ± 0.80 ng/g ww; ∑PFAS = 1.21 ± 2.97 ng/g ww; Hg = 20.17 ± 7.52 ng/g dw). PCB concentrations in eggs increased with later hatch date, independently of lipid content which also increased over time. Some females may remobilize and transfer more PCBs to their eggs, by delaying migration several weeks, relying on more polluted and stored resources, or being in poor body condition when arriving at the breeding grounds. PFAS and Hg occurrence in eggs did not change throughout the breeding season, suggesting migration has a greater effect on lipophilic pollutants. Pollutant exposure during offspring production in Arctic-breeding migrants may result in different profiles, with effects becoming more apparent with increasing trophic levels.

• Poste, Amanda E; Hoel, Cathrine Skaar; Andersen, Tom; Arts, Michael T; Færøvig, Per-Johan & Borgå, Katrine (2019). Terrestrial organic matter increases zooplankton methylmercury accumulation in a brown-water boreal lake. Science of the Total Environment. ISSN 0048-9697. 674, s. 9–18. doi: 10.1016/j.scitotenv.2019.03.446. Fulltekst i vitenarkiv Vis sammendrag

  Increases in terrestrial organic matter (tOM) transport from catchments to boreal lakes can affect methylmercury (MeHg) accumulation in aquatic biota both directly by increasing concentrations of aqueous MeHg, and indirectly through effects on MeHg bioavailability and on energy pathways in the lower food web. We carried out a detailed seasonal study of water chemistry, zooplankton diet, and MeHg accumulation in zooplankton in two lakes with contrasting tOM concentrations. Between-lake differences explained 51% of the variability in our water chemistry data, with no observed effect of season or sampling depth, contrary to our expectations. Higher tOM was correlated with higher aqueous Hg concentrations, lower areal pelagic primary productivity, and an increased contribution of terrestrial particles to pelagic particulate organic matter. Based on dietary marker analysis (δ13C, δ15N, and fatty acid [FA] composition), zooplankton diet was strongly linked to feeding mechanism, with dietary reliance on phytoplankton highest in the selective-feeding calanoid copepods, and lowest in filter feeding cladocerans. Zooplankton dietary reliance on phytoplankton and their concentrations of high-quality lipids, including polyunsaturated fatty acids, were higher in the clear-water lake than in the brown-water lake, where bacterial and terrestrial food sources were more prevalent. MeHg was highest in zooplankton from the brown-water lake, with highest concentrations in the 200–500 μm zooplankton size fraction for both lakes. Contrary to our expectations, there was no effect of season on zooplankton dietary markers or MeHg. Our results suggest that, overall, higher tOM results in higher MeHg concentrations in water and zooplankton, and reduces zooplankton dietary reliance on phytoplankton. Increased tOM thus leads to a decrease in the nutritional quality of zooplankton (i.e. higher MeHg concentrations, and lower concentrations of essential fatty acids), which may cascade up the food web with negative implications for higher trophic levels.

• Hitchcock, Daniel James; Andersen, Tom; Varpe, Øystein & Borgå, Katrine (2019). Effects of Maternal Reproductive Investment on Sex-Specific Pollutant Accumulation in Seabirds: A Meta-Analysis. Environmental Science and Technology. ISSN 0013-936X. 53(13), s. 7821–7829. doi: 10.1021/acs.est.9b01296. Fulltekst i vitenarkiv
• Andersen, Tom; Elburg, Marlina Augusta; Niekerk, Herman S. van & Ueckermann, Henriette (2018). Successive sedimentary recycling regimes in southwestern Gondwana: Evidence from detrital zircons in Neoproterozoic to Cambrian sedimentary rocks in southern Africa. Earth-Science Reviews. ISSN 0012-8252. 181, s. 43–60. doi: 10.1016/j.earscirev.2018.04.001. Fulltekst i vitenarkiv
• Khomich, Maryia; Cox, Filipa; Andrew, Carrie Joy; Andersen, Tom; Kauserud, Håvard & Davey, Marie Louise (2018). Coming up short: Identifying substrate and geographic biases in fungal sequence databases. Fungal ecology. ISSN 1754-5048. 36, s. 75–80. doi: 10.1016/j.funeco.2018.08.002. Fulltekst i vitenarkiv Vis sammendrag

  Insufficient reference database coverage is a widely recognized limitation of molecular ecology ap-proaches which are reliant on database matches for assignment of function or identity. Here, we use datafrom 65 amplicon high-throughput sequencing (HTS) datasets targeting the internal transcribed spacer(ITS) region of fungal rDNA to identify substrates and geographic areas whose underrepresentation in theavailable reference databases could have meaningful impact on our ability to draw ecological conclu-sions. A total of 14 different substrates were investigated. Database representation was particularly poorfor the fungal communities found in aquatic (freshwater and marine) and soil ecosystems. Aquaticecosystems are identified as priority targets for the recovery of novel fungal lineages. A subset of the datarepresenting soil samples with global distribution were used to identify geographic locations andterrestrial biomes with poor database representation. Database coverage was especially poor in tropical,subtropical, and Antarctic latitudes, and the Amazon, Southeast Asia, Australasia, and the Indian sub-continent are identified as priority areas for improving database coverage in fungi.

• Andersen, Tom; Elburg, Marlina & Erambert, Muriel (2018). Contrasting trends of agpaitic crystallization in nepheline syenite in the Pilanesberg Alkaline Complex, South Africa. Lithos. ISSN 0024-4937. 312-313, s. 375–388. doi: 10.1016/j.lithos.2018.05.015. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Riis-Pedersen, Christine; Carlsen, Eira Catharine Lødrup; Hessen, Dag Olav; Lejzerowicz, Franck Laurent Patrick; Andersen, Tom & Dörsch, Peter [Vis alle 8 forfattere av denne artikkelen] (2025). Microbial drivers of methane cycling in meromictic as compared to holomictic lakes. Fulltekst i vitenarkiv
• Nyeggen, Margot Ulfsdatter; Christiansen, Svenja; Garvang, Even Sletteng; Andersen, Tom; Heuschele, Jan David & Titelman, Josefin (2025). Zooplankton community dynamics in Oslofjorden. Fulltekst i vitenarkiv
• Garvang, Even Sletteng; Heuschele, Jan David; Konestabo, Heidi Sjursen; Andersen, Tom; Riemann, Lasse & Titelman, Josefin (2025). Replication Data for: Parasite infection shapes the pathobiome and behavior of marine zooplankton. doi: https:/scholar.google.com/citations?view_op=view_citation&hl=sv&user=ycTVkNkAAAAJ&sortby=pubdate&citation_for_view=ycTVkNkAAAAJ%3A3s1wT3WcHBgC. Fulltekst i vitenarkiv Vis sammendrag

  We collected Calanus helgolandicus from the Oslofjord, both healthy individuals and infected with a conspicuous" yellow-hyphal" parasite that changes the host behavior. We incubated them for 7 days and measured behavior and survival. At the start and end of the incubation we sampled animals for 16S rRNA microbial community analysis. Infected Calanus had higher mortality, more risky behavior and altered microbiomes compared to the uninfected.

• Heuschele, Jan David; Markova, Yana; Striebel, Maren; Andersen, Tom & Titelman, Josefin (2025). Uferflucht - Shore avoidance and other zooplankton dynamics in a coastal ecosystem. Fulltekst i vitenarkiv
• Giebichenstein, Julia; Dupont, Nicolas; Harju, Mikael; Varpe, Øystein; Gabrielsen, Geir W. & Andersen, Tom [Vis alle 7 forfattere av denne artikkelen] (2025). Seasonal Insights into Pollutant Accumulation and Biomagnification in an Arctic Marine Food Web. Fulltekst i vitenarkiv
• Garvang, Even Sletteng; Heuschele, Jan David; Konestabo, Heidi Sjursen; Andersen, Tom; Riemann, Lasse & Titelman, Josefin (2025). Parasite infection shapes the pathobiome and behavior of copepods. Fulltekst i vitenarkiv
• Kline, Simon Hasselø; Saubrekka, Karoline; Eikrem, Wenche; Valestrand, Louise; Egge, Elianne Dunthorn & Eiler, Alexander [Vis alle 8 forfattere av denne artikkelen] (2024). Seasonal dynamics of the protist community in the Oslofjord and Skagerrak in a changing ocean. Fulltekst i vitenarkiv Vis sammendrag

  Protists and prokaryotes compose approximately 90% of the biomass in the oceans, and any changes within this microbial community are likely to have reverberating effects throughout the ecosystem. Due to climate coastal marine systems are experiencing increased freshwater discharge from land and a darkening of the water column along with changes in nutrient concentrations. The phenology is also changing and in the inner Oslofjord the spring blooms starts on average 2 weeks later that 15 years ago. The causes for this delay in unclear. In this study we examine the diversity and seasonal dynamics of the protist community by metabarcoding in the inner and outer Oslofjord, and possible changes during 14 years. Monthly plankton samples were collected at two localities and two depths during 2023 and similar samples were collected in 2009-2011, to be sequenced by current high throughput technology (Illumina). Various environmental parameters have been measured including CDOM (colored dissolved organic matter). We ask whether browning or other physico-chemical conditions can explain the delayed spring bloom and other observed changes in the protist community in the Oslofjord and Skagerrak.

• Myrann, Olav; Kline, Simon Hasselø; Andersen, Tom & Edvardsen, Bente (2024). The effects of light and salinity on growth of spring bloom diatoms in the Oslofjord. Fulltekst i vitenarkiv Vis sammendrag

  Diatoms dominate during the spring bloom in the Oslofjord, with members of the genera Skeletonema, Thalassiosira and Chaetoceros being among the most abundant. During the last 15 years there has been a recorded reduction in Skeletonema abundance during the spring bloom in the Inner Oslofjord, that may explain an overall reduction of diatom abundance. In comparison the concentration of other diatoms such as Chaetoceros spp. has remained stable in the same period. The concentration of dinoflagellates has remained stable in contrast to the decrease of diatom concentration since 2006. The main aim of this master’s project is to obtain further knowledge on the abiotic factors affecting the important spring bloom diatom genera Skeletonema, Chaetoceros and Thalassiosira, and how environmental changes may affect their growth. To reach these aims, two different growth experiments using diatom cultures isolated from the spring bloom in the Oslofjord will be employed: 1) growing strains of Skeletonema and Chaetoceros separately under a combination of varying salinity and light intensity, and 2) conducting a common garden growth experiment with cultures of two additional diatom cultures Chaetoceros and Thalassiosira resulting in 4 species in total. The common garden growth experiment will test various conditions of salinity. The project will give insight into the dynamics of the spring blooming diatoms in the Oslo fjord and how they are affected by changes in salinity along with their interactions.

• Eliassen, Sigurd, skaar; Kline, Simon Hasselø; Andersen, Tom & Edvardsen, Bente (2024). Investigating the phytoplankton spring bloom dynamics n the Oslofjord by single species and common garden growth experiments. Fulltekst i vitenarkiv Vis sammendrag

  During the last 15 years there has been a gradual decrease of diatom concentration during the spring bloom in the inner Oslofjord. A part of this decrease may be explained by decrease of the concentration of the genus Skeletonema, while other important diatom genera such as Chaetoceros and Thalassiosira have maintained a stable concentration since 2006. The reason for this is unclear. Possible causes for these changes include changes of the physical or chemical conditions. One potential driver of the observed changes can be coastal darkening due to climate change leading to shifting phytoplankton dynamics in the inner Oslofjord. An increase of light absorbing molecules of dissolved coloured organic matter (cDOM) transferred to the fjord from river input could reduce the growth of phytoplankton and potentially also shift the spring bloom to a later date. Under conditions with limited light, the phytoplankton taxa with the ability to grow at the lowest light intensity may be able to outcompete other competitors for the available light. The aim of this master’s project is to get a better understanding of the dynamics of important spring bloom diatoms in the Oslofjord and possible explanations to the observed changes. By single-species growth experiments I will determine the compensation light intensity of strains of two diatom genera Chaetoceros and Thalassiosira grown at different salinities. In a common garden experiment strains of the two diatom genera will be grown together with a strain of Skeletonema under different light conditions, to determine their competitive ability to limiting irradiance. This may contribute to a better understanding of the changes in the spring bloom dynamic observed in the Oslofjord since 2006.

• Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind; Hessen, Dag Olav; Andersen, Tom & Aksnes, Dag Lorents (2024). Land use change and coastal water darkening drive synchronous dynamics in phytoplankton and fish phenology on centennial time scales. Fulltekst i vitenarkiv
• Edvardsen, Bente; Fon, Mathias; Reitzel, Helene; Šupraha, Luka; Andersen, Tom & Uhlig, Silvio (2023). Growth preferences of the haptophyte Chrysochromulina leadbeateri forming ichthyotoxic blooms in fjords in N Norway. Fulltekst i vitenarkiv Vis sammendrag

  Microalgal flagellates of the genera Chrysochromulina and Prymnesium may form extensive blooms in marine and brackish waters causing fish kills. Chrysochromulina leadbeateri blooms caused massive fish kills in fish farms in Northern Norway in May 1991 and 2019. More than 14 500 tons of farmed salmon died in 2019. Cultures from both blooms were used in physiological experiments to investigate possible causes for the blooms. Growth experiments with varying salinity, temperature and irradiance in a facultative design were performed. Highest growth rates were obtained at temperatures 11-15 oC and salinities 25-30, and the tolerance range for growth were between 4-15 oC and salinities 20-34. Under optimal conditions, growth rates increased with irradiance (up to 100 µmol photons m-2 s-1). During the bloom in 2019, highest C. leadbeateri concentrations were found in waters with slightly reduced salinity (32-33) and sea surface temperatures around 7oC. Strains from the blooms in 1991 and 2019 were identical in the 18S rRNA gene. This ribotype appears to have a cold water-Arctic geographical distribution based on the metaPR2 metabarcoding datasets, whereas other ribotypes of C. leadbeateri in this dataset show a cosmopolitan or temperate-warm water distribution. We suggest that C. leadbeateri consists of several ribotypes with different growth preferences and that the toxic blooms in Northern Norway were formed by a ribotype adapted to cold waters with slightly reduced salinity and can tolerate rather high irradiances. Possible causes for the ichthyotoxic blooms will be discussed.

• Eliassen, Lasse Krøger; Garvang, Even Sletteng; Andersen, Tom; Engseth, Erik; Kristiansen, Kåre Andre & Wiik-Nielsen, Jannicke [Vis alle 7 forfattere av denne artikkelen] (2023). A parasite-copepod association and its effects on host pigmentation and lipids. Fulltekst i vitenarkiv
• Schultze, Sabrina; Langva, Hilde K.; Knudtzon, Nina Cathrine; Chatzigeorgiou, Marios; Rundberget, Jan Thomas & Brooks, Steven [Vis alle 11 forfattere av denne artikkelen] (2023). Increases in Terrestrial Dissolved Organic Matter Will Not Increase Feeding Related Uptake of a common Lipid Soluble Contaminant In coastal Filter Feeders. Fulltekst i vitenarkiv
• Schultze, Sabrina; Langva, Hilde K.; Knudtzon, Nina Cathrine; Chatzigeorgiou, Marios; Rundberget, Jan Thomas & Brooks, Steven [Vis alle 11 forfattere av denne artikkelen] (2023). Terrestrial dissolved organic matter is not an efficent vector for lipohilic contaminants in filter feeders. Fulltekst i vitenarkiv
• Fon, Mathias; Supraha, Luka; Andersen, Tom; Uhlig, Silvio & Edvardsen, Bente (2023). Using high-throughput techniques to understand the growth of the fish-killing haptophyte Chrysochromulina leadbeateri in northern Norway. Fulltekst i vitenarkiv
• Samdal, Ingunn Anita; Uhlig, Silvio; Solhaug, Anita; Fon, Mathias; Gilbert, Dorothea & Ivanova, Lada [Vis alle 15 forfattere av denne artikkelen] (2023). Toxic microalgae in Norwegian waters - Uncovering fish-killing mechanisms of phytoplankton from Scandinavian waters. Fulltekst i vitenarkiv
• Giebichenstein, Julia; Harju, Mikael; Varpe, Øystein; Gabrielsen, Geir Wing; Andersen, Tom & Borgå, Katrine (2023). Across the Seasons: Persistent Organic Pollutants in an Arctic Pelagic Food Web. Fulltekst i vitenarkiv
• Opdal, Anders Martin Frugård; Andersen, Tom; Hessen, Dag Olav; Lindemann, Christian & Aksnes, Dag Lorents (2023). Tracking freshwater browning and coastal water darkening from boreal forests to the Arctic Ocean. Fulltekst i vitenarkiv
• Saubrekka, Karoline; Vader, Anna; Supraha, Luka; Andersen, Tom & Edvardsen, Bente (2023). Diversity and Distribution of Arctic Protists in Pelagic and Sympagic Habitats in the Northern Barents Sea as Revealed by Metabarcoding. Fulltekst i vitenarkiv
• Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind; Hessen, Dag Olav; Andersen, Tom & Aksnes, Dag Lorents (2023). Tracking freshwater browning and coastal water darkening from boreal forests to the Arctic Ocean. Fulltekst i vitenarkiv
• Giebichenstein, Julia; Warner, Nicholas Alexander; Routti, Heli Anna Irmeli; Harju, Mikael; Varpe, Øystein & Andersen, Tom [Vis alle 8 forfattere av denne artikkelen] (2023). Emerging contaminant accumulation in an Arctic marine food web. Fulltekst i vitenarkiv
• Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind; Hessen, Dag Olav; Andersen, Tom & Aksnes, Dag Lorents (2023). Land use change and coastal water darkening drive synchronous dynamics in phytoplankton and fish phenology on centennial time scales. Fulltekst i vitenarkiv
• Garvang, Even Sletteng; Eliassen, Lasse Krøger; Titelman, Josefin & Andersen, Tom (2022). Modeling the parasites of copepods. Fulltekst i vitenarkiv
• Eliassen, Lasse Krøger; Garvang, Even Sletteng; Andersen, Tom; Engseth, Erik; Kristiansen, Kåre Andre & Wiik-Nielsen, Jannicke [Vis alle 7 forfattere av denne artikkelen] (2022). The yellow-hyphal parasite in Calanus finmarchicus. Fulltekst i vitenarkiv
• Gundersen, Madeleine S.; Morelan, Ian; Bakke, Ingrid; Andersen, Tom & Vadstein, Olav (2022). Disturbances increase selection – whereas stability promotes stochastic assembly in bacterial communities. Fulltekst i vitenarkiv
• Giebichenstein, Julia; Warner, Nicholas Alexander; Varpe, Øystein; Andersen, Tom; Gabrielsen, Geir W. & Borgå, Katrine (2022). Chlorinated paraffins in polar cod and capelin from the Barents Sea. Fulltekst i vitenarkiv
• Gundersen, Madeleine S.; Morelan, Ian; Andersen, Tom; Bakke, Ingrid & Vadstein, Olav (2022). Bacterial community assembly during disturbances. Fulltekst i vitenarkiv
• Giebichenstein, Julia; Warner, Nicholas Alexander; Varpe, Øystein; Gabrielsen, Geir W.; Andersen, Tom & Borgå, Katrine (2022). Chlorinated paraffins in Polar cod and capelin from the Barents Sea during the Arctic spring bloom. Fulltekst i vitenarkiv
• Schultze, Sabrina; Langva, Hilde K.; Nina, Knudtzon; Chatzigeorgiou, Marios; Rundberget, Thomas & Brooks, Steven [Vis alle 11 forfattere av denne artikkelen] (2022). Effect of terrestrial and aquatic dissolved organic matter on uptake of teflubenzuron in mussels and ascidians. Fulltekst i vitenarkiv
• Titelman, Josefin; Eliassen, Lasse Krøger; Garvang, Even Sletteng & Andersen, Tom (2021). Parasite disease in coastal zooplankton. Fulltekst i vitenarkiv
• Vogt, Rolf David; Andersen, Tom; Crapart, Camille Marie; Lie, Ragna O. & Hessen, Dag Olav (2021). Bionedbrytbarhet av løst naturlig organisk materiale i innsjøer. Naturen. ISSN 0028-0887. 5, s. 253–258. Fulltekst i vitenarkiv
• Schultze, Sabrina; Andersen, Tom; Knudtzon, Nina Cathrine; Ruus, Anders; Rundberget, Jan Thomas & Brooks, Steven [Vis alle 9 forfattere av denne artikkelen] (2021). Effect of terrestrial and aquatic dissolved organic matter on uptake rates of teflubenzuron in blue mussels (M. edulis). Fulltekst i vitenarkiv
• Titelman, Josefin; Eliassen, Lasse Krøger; Garvang, Even Sletteng & Andersen, Tom (2021). Parasite disease in coastal zooplankton. Fulltekst i vitenarkiv
• Allesson, Lina; Andersen, Tom; Dörsch, Peter; Eiler, Alexander; Wei, Jing & Hessen, Dag Olav (2020). Corrigendum: Phosphorus Availability Promotes Bacterial DOC-Mineralization, but Not Cumulative CO2-Production (Front.Microbiol, (2020), 11, (569879), 10.3389/fmicb.2020.569879). Frontiers in Microbiology. 11. doi: 10.3389/fmicb.2020.614974. Fulltekst i vitenarkiv
• Giebichenstein, Julia; Gopakumar, Anjali; Varpe, Øystein; Andersen, Tom; Gabrielsen, Geir W. & Borgå, Katrine (2020). Seasonal Variation of Mercury in an Arctic Marine Food Web. Fulltekst i vitenarkiv
• Gundersen, Madeleine Stenshorne; Morelan, Ian; Andersen, Tom; Bakke, Ingrid & Vadstein, Olav (2020). The effect of periodical disturbances on selection and drift in bacterial communities. Fulltekst i vitenarkiv
• Crapart, Camille Marie; Færgestad, Eline Mosleth; Andersen, Tom; Gundersen, Cathrine Brecke & Vogt, Rolf David (2020). Biodegradability of DNOM: Characterization and governing factors. Fulltekst i vitenarkiv
• Olsen, Thomas Meldahl; Augustsson, Ingrid Carita; Ravnås, Rodmar & Andersen, Tom (2020). Provenance on the Lange-Lysing mega-sequence on the Dønna Terrace: stratigraphic variability and lateral sandbody connectivity. Fulltekst i vitenarkiv
• Strand, David; Johnsen, Stein Ivar; Laurendz, Charlotte; Rusch, Johannes; Edsman, Lennart & Andersen, Tom [Vis alle 8 forfattere av denne artikkelen] (2019). Can eDNA quantities predict crayfish population density and/or A. astaci prevalence? Fulltekst i vitenarkiv
• Hitchcock, Daniel James; Loonen, M. J.; Warner, Nicholas Alexander; Herzke, Dorte; Tombre, Ingunn & Shimmings, Paul [Vis alle 10 forfattere av denne artikkelen] (2018). Migration effects on pollutants in eggs of Arctic - breeding geese. Fulltekst i vitenarkiv
• Rusch, Johannes; Strand, David; Laurendz, Charlotte; Johnsen, Stein Ivar; Edsman, Lennart & Andersen, Tom [Vis alle 7 forfattere av denne artikkelen] (2018). Simultaneous eDNA monitoring of the host-pathogen complex Pacifastacus leniusculus and Aphanomycis astaci under varying environmental conditions. Fulltekst i vitenarkiv Vis sammendrag

  In 2016 the North-American signal crayfish Pacifastacus leniusculus was included in the list of Invasive Alien Species of concern to the European Union. In Norway the species is black-listed and rated as a high-risk species and eradication has been carried out whenever feasible. This is because it is a chronic carrier of the oomycete Aphanomyces astaci, which is lethal to all European freshwater crayfish species and listed among the 100 worst invasive species. Environmental DNA (eDNA) methodology is now being used on a wide variety of target species and on many different platforms including targeted PCR and broad spectred sequencing methods. Detection and monitoring of invasive, endangered and elusive species is commonly performed using species specific quantitative real-time PCR (qPCR) or droplet digital PCR (ddPCR), and has proved useful for targeting species of specific concern. Recently eDNA monitoring of A. astaci has been implemented in the national crayfish plague surveillance in Norway. For the carrier of the crayfish plague, the signal crayfish, a qPCR assay for eDNA detection has also been published recently. In this study we present simultaneous eDNA monitoring of the host-pathogen complex P. leniusculus - A.astaci under varying environmental conditions both in aquarium and field experiments. We used the published qPCR assays for both species and redesigned them so they can be run as a duplex ddPCR assay. We compared water samples by means of qPCR and ddPCR from two lakes in Sweden and Norway with different signal crayfish population densities and A. astaci prevalence in the population. We also studied eDNA emission from the host-pathogen couple in aquarium-experiments with A. astaci positive signal crayfish held at different densities, temperatures and feeding regimes. Samples were obtained by filtering water (1 & 5 L) on-site through glass fibre filters. These were subsequently analysed using the species-specific qPCR and ddPCR assays for the respective targets. The concentrations of detectable eDNA copies of the two targets are influenced differently and by several factors, including population density of the crayfish, pathogen prevalence, temperature, and turbidity including microbiological activity in the water. They are therefore subject to significant fluctuation. Thus, there seems to be no straightforward correlation between eDNA copy-number and crayfish density and the probability of detecting one target rather than the other varies according to different conditions. Therefore, for a reliable monitoring of crayfish plague (A. astaci) and signal crayfish alone or together, the simultaneous monitoring concept for both targets is recommended.

• Lopez, Shirley Velasquez; Pasquo, Mercedes Di; Ruud, Caroline; Hatløy, Sveinung; Kristoffersen, Signe & Mehus, Trine [Vis alle 11 forfattere av denne artikkelen] (2018). Provenance of Ordovician(?) to Silurian strata in the Bolivian Altiplano. Fulltekst i vitenarkiv
• Fon, Mathias; Edvardsen, Bente; Solhaug, Anita; Uhlig, Silvio; Ivanova, Lada & Andersen, Tom (2025). Insight into the growth, toxicity and toxins of the fish-killing haptophyte Chrysochromulina leadbeateri. University of Oslo (UiO). Fulltekst i vitenarkiv
• Engseth, Erik; Titelman, Josefin & Andersen, Tom (2024). Constructing a conceptual food web of Oslofjord zooplankton using stable isotope analysis. Universitetet i Oslo. Fulltekst i vitenarkiv
• Sævarang, Brage; Titelman, Josefin & Andersen, Tom (2022). Kvantifisering av hoppekrepsparasitter med digitale fluorescens-bilder. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Hensikten med dette prosjektet var å utvikle en automatisert metode for å finne parasitter i hoppekreps. Jeg lette mer spesifikt etter Blastodinium som er en slekt av parasittiske dinoflagellater. Derfor ble det brukt propidiumjodid (PI), som er et stoff som fester seg på DNA. PI fluoriserer når det er bundet til DNA. Fordi dinoflagellatene har mer kompakt DNA lyste de mye sterkere enn hoppekrepsens kroppsvev. Det ble brukt en robot til å ta bilde av hele zooplanktonprøver, ikke bare enkeltdyr. Prøvene ble deretter analysert i bildebehandlingsprogrammet ImageJ med ZooProcess funksjonen. Denne funksjonen lager et eget bilde av hvert individ som var til stede i bildet. Det var flere av prøvene som viste tegn til parasitter. Metoden ble brukt på zooplankton-prøver fra et år i Oslofjorden. Tidsserien i Oslofjorden viste topper i parasittprevalens på over 10% i juni og juli. Parasittprevalensen for resten av året så ut til å holde seg rundt 5%. Det ble derfor vist at digitale fluorescens-bilder kan bli brukt til kvantifisering av hoppekrepsparasitter.

• Rusch, Johannes; Vrålstad, Trude; Strand, David; Andersen, Tom & Hansen, Haakon (2021). Environmental DNA (eDNA) monitoring of two different freshwater host-pathogen complexes in the interface between nature and aquaculture. Universitetsforlaget. Fulltekst i vitenarkiv
• Ringvold, Halldis; Johnsen, Geir & Andersen, Tom (2021). Studies on Echinodermata from the NE Atlantic Ocean - Spatial distribution and abundance of Asteroidea, including taxonomic and molecular studies on Crossaster and Henricia genera - Value-chain results, including test fishery, biology, market and nutritional analysis on Parastichopus tremulus (Holothuroidea) from the Norwegian coast. Norges teknisk-naturvitenskapelige universitet. ISSN 9788232668526. Fulltekst i vitenarkiv Vis sammendrag

  The phylum Echinodermata represent a large part of the marine benthic ecosystem biomass (up to 90%), and are also important in determining habitat structure for other species, and maintaining high species diversity in the marine ecosystems. The phylum contains five classes (Asteroidea, Holothuroidea, Ophiuroidea, Crinoidea and Echinoidea), of which studies on both asteroids and holothuroids from the NE Atlantic Ocean are presented here. With the establishment of nations Exclusive Economic Zone at the end of the 1970s, nations acquired scientific responsibility for a larger area than previously controlled as well as the jurisdictionto governtheuseof their marine resources. Scarce knowledge on benthic fauna from the NE Atlantic Ocean (mainly before 1950), led to increased efforts in mapping biodiversity. In order to increase knowledge about invertebrates, including echinoderms, around the Faroe Islands, the «Marine benthic fauna of the Faroe Islands» (BIOFAR) programme was implemented. The programme conducted systematic sampling down to about 2400 m depth during the period between 1987 and 1990. Based on positive experience from BIOFAR, another programme, «Benthic Invertebrates of Icelandic Waters» (BIOICE), was formed a few years later, following somewhat the same principles. Data from both programmes, as well as a few other areas, are included in the studies on spatial distribution and abundance of Asteroidea, including taxonomic and molecular studies on Crossaster and Henricia genera, from the NE Atlantic Ocean. Also, holothuroids (sea cucumbers) are considered a delicacy on the Chinese market, with increasing demand from consumers. With increasing interest for a Norwegian fishery on Parastichopus tremulus, but with limited knowledge on fishery, biology, production and the Chinese market, several pilot projects were begun. These projects took place along the Norwegian coast between 2000 and 2006, with follow up scientific cruises. This doctoral thesis comprises three sub-aims, of which the first was to analyse distribution and abundance of asteroids from the NE Atlantic Ocean, using data obtained mainly from the Faroe Islands and Iceland. With the inclusion of asteroids from published literature, the total results show that 50 species have been recorded from the Faroe Islands, 64 from Iceland, and, although not included in these studies, 50 have been reported from nearby Norway, making Iceland the most species-rich area. Within the upper continental slope and the water mass transition zone, the most species-rich depth intervals from the Faroe Islands were identified with 33-34 species from 500-700 m depth. The two most species-rich depth intervals from Iceland showed only 23-24 species from 100-200 m and 400-500 m depth. All species showed different preferences regarding abundance-weighted depth- and temperature, although somewhat the same shallow-, intermediate- and deep-water species from the two programmes could be grouped. Non-metric Multidimensional Scaling (NMDS) from both programmes captured the same environmental gradients (depth and temperature). Asteroid accounts from the Faroe Islands and Iceland may become important basic reference data for future studies on climate change and shift in species distribution in these highly productive seas. A second sub-aim of this study was to conduct in-depth analyses on two frequently encountered genera in the NE Atlantic Ocean (also the Faroe Islands and Iceland), Crossaster and Henricia, using both morphological and molecular methods. These genera are known for morphological variability and taxonomic confusion. Genetic analysis using DNA sequences COI and ITS1 supported the morphology studies indicating that C. papposus and C. squamatus are clearly distinct taxa, yet closely related. C. papposus is mainly found in temperate shallow waters, whereas C. squamatus is manly found on the shelf-break in colder, mixed water masses. Morphological studies on 796 Henricia specimens showed they could easily be assigned to either the «H. pertusa group» or «H. perforata group» mainly due to thorn- or blunt-shaped dorsal spines. Using DNA barcoding (COI and 16S regions), five well-supported genetic clades were revealed by maximum likelihood analysis. Re-evaluation of individuals from the different clades allowed us to confirm species identification for three of the clades: Henricia pertusa, H. perforata and H. oculata. Given the morphological variation within both Crossaster and Henricia genera, a combination of morphological and molecular studies is shown to be useful for species identification, and the methods are applicable for other studies aiming for a more accurate mapping of species richness and biodiversity. Diversity of asteroids is still poorly known and underestimated in certain areas of the world e.g. hampering the assessment of the origin and evolution of the class. A third sub-aim of this thesis was to analyse Parastichopus tremulus data on catches, locations, length, sediment and market from a pool of sources, including pilot-projects with data obtained from fishing boats and by-catch fisheries from both northern and southern Norway, as well as scientific cruises. Results showed that P. tremulus is distributed all along the Norwegian coast, but with a patchy distribution, showing preference for gravelly sand. The largest trawl catches were taken from depths of ~100–300 m. Market analysis showed nutritional content were appreciated by Chinese customers, with a high protein and a low-fat content resembling levels of other holothuroids. High levels of polyunsaturated fatty acid EPA (eicosapentaenoic acid, C20:5 n-3, Omega 3) were specific for this cold-water species, in comparison to tropical species. Production and marketing tests showed a prosperous commercial potential on the Chinese market. Overall, these advances in scientific knowledge have potential applications as baseline data for future studies on climate change, mapping of biodiversity and fishery.

• Gundersen, Cathrine Brecke; Vogt, Rolf David; Lundanes, Elsa; Breedvelt, Gijs & Andersen, Tom (2018). Environmental fate of nitramines formed during amine-based post-combustion CO2 capture. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  There is now international political agreement to reduce greenhouse gas emissions to limit global warming by 2 °C1. Technology for amine-based CO2 capture offers the opportunity of reducing emission from already existing large-scale point sources. A thorough risk assessment of the technology is lacking. Ongoing investigations point to the formation of potentially carcinogenic and stable nitramines as the greatest risk. This study contributes to the risk assessment by investigating the soil sorption of nitramines and the response from environmental bacteria to the nitramines. Soil sorption is the most important process for retaining chemicals in the terrestrial environment. Bacteria are of interest since they can potentially degrade nitramines, but not if the nitramines pose toxic effects on the bacteria. Focus was on MEA (monoethanol)-, MMA (monomethyl)-, and DMA (dimethyl)-nitramines. To enable these studies, a method for nitramine determination in relevant sample matrices had to be optimized. Soil sorption was studied using a batch experimental setup and quantified indirectly by measuring loss of nitramine from the aqueous phase after equilibrium had been established with the soil. Potential toxic effect on bacteria was assessed by studying the response parameters of aerobic respiration, carbon utilization, and growth. During these experiments the biodegradability of the nitramines was also tested. Both environmental bacterial communities and pure cultures of isolated strains were included. Liquid chromatography–tandem mass spectrometry (LC-MS/MS) was used for the determination of nitramines. The final optimized version of the method, presented in Paper 2, is the first thorough validation for the simultaneous determination of multiple nitramines available in peer-reviewed literature. The method consists of reversed phase separation (C18) and electrospray ionisation with polarity switching mode, and can be used to detect low µg L-1 level nitramines in various aqueous matrices. Paper 3 provides evidence for a weak binding of MEA- and DMA-nitramines to soils rich in organic matter. Thus, accumulation can occur in organic rich soil layers, potentially hindering the nitramines from reaching e.g. the ground water. Different types of environmental bacteria were found to exert an ambiguous response towards the nitramines. For example, toxic effect was observed towards MEA-nitramine in a bacterial lake community (Paper 4). Contrary to this, no toxic response, but approximately 10% biodegradation of all three nitramines occurred in a pure culture of Pseudomonas fluorescens (Paper 5). The research presented in Papers 1-5 has been conducted using nitramine exposure levels at least three orders of magnitude higher than the levels that can be expected in precipitation in the vicinity of amine-based CO2 capture facilities. Future studies should aim at improving the sensitivity of the LC-MS/MS method. This would allow for detection of nitramines at environmentally relevant conditions, both from amine-based CO2 capture and from other alternative sources of nitramine formation.

• Rajakumar, Janaki; Vogt, Rolf David & Andersen, Tom (2018). Effect of Photo-Oxidation on Size, Structure and Biodegradability of Dissolved Natural Organic Matter. Universitetet i Oslo. Fulltekst i vitenarkiv

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