Silvia Hess

• Freitas, Thaise Ricardo de; Nomaki, Hidetaka; Hess, Silvia; Renaud, Paul; Ogawa, Nanako O. & Ohkouchi, Naohiko [Vis alle 8 forfattere av denne artikkelen] (2026). Effects of temperature and food availability on Arctic benthic foraminifera: coupling field observations with feeding experiments. Marine Ecology Progress Series. ISSN 0171-8630. doi: 10.3354/meps15237. Fulltekst i vitenarkiv Vis sammendrag

  Climate-driven increases in primary production are expected to alter the organic matter reaching the Arctic seafloor. While polar organisms can respond rapidly to changes in food pulses, there is limited information on how different benthic compartments exhibit distinct physiological and population-level responses. Here, we evaluated the responses of benthic foraminifera to the addition of 13C-labelled algae powder under ambient conditions and a warmer temperature setting. We quantified the species-specific ingestion rates of selected foraminifera taxa from shelf and slope regions characterised by distinct water depths and hydrographic conditions. Our results demonstrated that shelf foraminiferal assemblages had higher uptake than slope assemblages, despite the latter having generally higher abundance. Both suspension feeders and detritivores (e.g., Saccorhiza ramosa and Cribrostomoides subglobosus, respectively) had high feeding rates, indicating that species-specific uptake is related to feeding preferences and strategies. Most taxa did not exhibit increased feeding under warm conditions, except for C. subglobosus and certain calcareous taxa, suggesting that warming effects are secondary and species-specific. Background foraminiferal isotopic signatures (δ13C, δ15N) evidenced trophic plasticity in Arctic benthic foraminifera, as Lagenammina difflugiformis, Elphidium clavatum and Melonis affinis showed varying isotopic values across sites. Our findings indicate that future warming may alter benthic carbon cycling not through generalised metabolic acceleration due to higher water temperature, but through species-specific shifts that should restructure community biodiversity and trophic roles.

• Górska, Barbara; Grzelak, Katarzyna; Bluhm, Bodil; Hess, Silvia & Włodarska-Kowalczuk, Maria (2025). Does mesh size matter? Influence of mesh size on estimation of meiofauna abundance, biomass and on size spectra. Oceanologia. ISSN 0078-3234. 67(4). doi: 10.5697/rxwv1889. Fulltekst i vitenarkiv Vis sammendrag

  For muddy-bottom meiofauna analyses, samples are typically sieved on 32 𝜇m sieves for animal extraction. However, some studies use a 63 𝜇m sieve to reduce fine sediment overload. Such variation in sieving protocols hampers comparisons across studies. We quantified and compared the effects of mesh size (63 versus 32 𝜇m) on meiofauna abundance, biomass, community composition, and size spectra in muddy sediments. Between 8 and 21% of individuals (mostly nematodes) were missed in the 63 𝜇m mesh-based analyses (compared to 32 𝜇m). However, the larger mesh size did not affect biomass estimations or the construction of size spectra. For muddy sediments, a 63 𝜇m sieve can be used interchangeably with a 32 𝜇m sieve for meiofauna biomass estimation.

• Kohlbach, Doreen; Fransson, Agneta; Arumí, Martí Amargant; Assmann, Karen; Assmy, Philipp Kurt Wolf & Bratbak, Gunnar [Vis alle 38 forfattere av denne artikkelen] (2025). Nansen and Amundsen basins: Gradients of physico-chemical properties and biota composition with implications for future resource management of the central Arctic Ocean. Elementa: Science of the Anthropocene. 13(1). doi: 10.1525/elementa.2024.00016. Fulltekst i vitenarkiv Vis sammendrag

  The projected transition of the central Arctic Ocean (CAO) into a warmer, seasonally ice-free ocean requires more knowledge of this environment to predict changes in the structure and dynamics of its ecosystems. We aimed to compare the state and underlying processes of Nansen Basin and Amundsen Basin ecosystems observed in August–September 2021 and assess impacts of Atlantic Water inflow and fresher Transpolar Drift waters, respectively, on these ecosystems. The basins differed in features of sea ice, hydrography, and chemical and biological compositions. The near-slope open water in western Nansen Basin showed a clear fingerprint of warm, saline Atlantic Water, with larger vertical turbulent fluxes facilitating nutrient transport across the pycnocline and supporting larger standing stocks of bacteria, protists, and zooplankton. Pelagic primary production and microbial and faunal stocks decreased northward and into Amundsen Basin, likely due to lower nutrient concentrations, stronger stratification, and reduced light through the more continuous and thicker ice and snow cover in Amundsen Basin, possibly also impacted by seasonally declining light levels. Transpolar Drift signals included lower salinity, stronger stratification, and higher silicate concentrations in Amundsen Basin surface waters. Similarities to earlier observations included the increase in small-sized algae from Nansen Basin into Amundsen Basin and overall low faunal abundances in the CAO, suggesting that overarching patterns remained unchanged over past decades. Examples of species range extensions and notable taxon absences relative to earlier studies, however, could be due to borealization and changes in sea-ice conditions, respectively. Higher density ecosystem sampling and consistent time series are recommended to confirm such conclusions. The distinct basin differences call for a regional approach to future management of the CAO. We especially caution against using the area of strong Atlantic Water inflow in southern Nansen Basin as representative of the entire basin, let alone Amundsen Basin or the CAO.

• Freitas, Thaise Ricardo de; Hess, Silvia; Renaud, Paul Eric; Appleby, Peter & Alve, Elisabeth (2024). Drivers of organic carbon distribution and accumulation in the northern Barents Sea. Progress in Oceanography. ISSN 0079-6611. 225. doi: 10.1016/j.pocean.2024.103286. Fulltekst i vitenarkiv Vis sammendrag

  Sedimentary properties and accumulation rates on the continental shelf and in the deep sea reflect temporal oceanographic, biological and chemical processes occurring in the water column and the sediment surface. We used the radionuclides 210Pb, 226Ra, and 137Cs activities to estimate sedimentation rates during the last century at nine stations in the northern Barents Sea region. Elemental (C, N) and stable isotopic composition (δ13C, δ15N) were also analysed from the nine stations sampled in August 2018, and, for five other stations sampled in August and December 2019, and in March and May 2021. Sediment accumulation rates varied between 130 and 1 410 g m−2 y−1. The < 63 μm normalized total organic carbon (TOC63) and the total nitrogen from the sediment surface varied between 0.90–2.56 % and 0.13–0.33 %, respectively. Ice-free shelf stations had higher TOC63 and possibly fresher organic matter (high δ13C, low δ15N) than ice-covered more northern stations. The opposite trend was observed for total inorganic carbon. We found that these trends in biogeochemical parameters were spatially structured by the winter sea ice concentration and biological production differences, and exhibited a south-north separation of the Polar Front region. The low and stable organic carbon accumulation rate (1.7–13.4 g Corg m-2 y−1; ARtoc) is a function of slow sedimentation rates, and high degradation and residence time in the water column and at the sediment–water interface. Overall, the ARtoc has been stable for the past 100 years, with a slight increase from the early 1970s to the present at the shelf and slope stations. Our results highlight that spatial scales of variability of the studied sedimentary parameters are linked to spatial patterns of important environmental variables (e.g., chlorophyll-a, sea ice concentration) in the region. In contrast, no seasonal differences were observed in the sediment parameters of revisited stations, and the dated sediment geochemical profiles did not exhibit substantial longer-term variation. This means that climate-induced changes in variables that modify the sedimentary geochemistry of the environment may affect benthic community activity and structure before leaving a record in ARtoc.

• Sen, Arunima; Molina, Èric Jordà; Freitas, Thaise Ricardo de; Hess, Silvia; Reiss, Henning & Bluhm, Bodil Annikki Ulla Barbro [Vis alle 7 forfattere av denne artikkelen] (2024). Benthic remineralization under future Arctic conditions and evaluating the potential for changes in carbon sequestration in warming sediments. Scientific Reports. 14(1). doi: 10.1038/s41598-024-73633-z. Fulltekst i vitenarkiv Vis sammendrag

  Benthic (seafloor) remineralization of organic material determines the fate of carbon in the ocean and its sequestration. Bottom water temperature and labile carbon supply to the seafloor are expected to increase in a warming Arctic and correspondingly, benthic remineralization rates. We provide some of the first experimental data on the response of sediment oxygen demand (SOD), an established proxy for benthic remineralization, to increased temperature and/or food supply across a range of Arctic conditions and regimes. Each factor significantly increased SOD rates (with different degrees of variability); however the largest increases were seen with both factors combined (50% to ten-fold increases), consistently across the four seasons and the spatial gradient covering shelf to deep basin included in our study. This ability of the Arctic benthos to process increased pulses of carbon suggests that increased sedimented carbon under warming conditions is likely to be utilized and processed, not accumulated, impacting carbon storage and decreasing the Arctic’s role as a global carbon sink.

• Appleby, Peter G.; Piliposyan, Gor & Hess, Silvia (2021). Detection of a hot 137Cs particle in marine sediments from Norway: potential implication for 137Cs dating. Geo-Marine Letters. ISSN 0276-0460. 42. doi: 10.1007/s00367-021-00727-2. Fulltekst i vitenarkiv
• Klootwijk, Anouk Tosca; Sweetman, Andrew K.; Hess, Silvia; Alve, Elisabeth; Dunlop, Kathrine M. & Renaud, Paul Eric (2021). Benthic foraminiferal carbon cycling in coastal zone sediments: The influence of the assemblage structure and jellyfish detritus. Estuarine, Coastal and Shelf Science. ISSN 0272-7714. 261. doi: 10.1016/j.ecss.2021.107535. Fulltekst i vitenarkiv
• Klootwijk, Anouk Tosca; Alve, Elisabeth; Hess, Silvia; Renaud, Paul Eric; Sørlie, Carsten & Dolven, Jane Karine Lønne (2020). Monitoring environmental impacts of fish farms: Comparing reference conditions of sediment geochemistry and benthic foraminifera with the present. Ecological Indicators. ISSN 1470-160X. 120. doi: 10.1016/j.ecolind.2020.106818. Fulltekst i vitenarkiv Vis sammendrag

  Intensive fish farming is a major industry, but the extent of organic matter (OM) and heavy metal pollution by fish farms is debated. This study established in situ reference conditions using geochemical parameters and fossil benthic foraminiferal assemblages in dated sediment cores to identify potential impacts of fish farming in two basins of the inner Øksfjord, Northern Norway. Living (rose Bengal stained) benthic foraminifera were used to assess the present day environmental conditions. The fossil foraminiferal records were compared with the living foraminifera, which in turn were compared with macrofaunal data. Long-term (> 100 yrs) sediment core records of the geochemical parameters (TOC63, C/N, δ13CVPDB TOC and heavy metals) and foraminiferal indices (Norwegian Quality Index (fNQI), AZTI’s Marine Biotic Index (fAMBI), fHlog2, ES100) did not indicate an impact from fish farming through time. Long-term changes in foraminiferal absolute abundances and relative abun- dances of ecological groups (EGs) reflecting organic matter (OM) tolerance suggest that the OM supply slightly increased compared to reference conditions. Relative abundances of Brizalina skagerrakensis and Epistominella vitrea, previously associated with phytodetrital input, suggest a minor increase in primary productivity com- pared to reference conditions. The Stainforthia group (S. fusiformis and S. feylingi), indicative of OM enrichment, in the living foraminiferal assemblages may indicate a response to fish farming activities, but foraminiferal seasonality could not be excluded as a potential cause. The indices of both fossil and living foraminifera, in addition to the macrofauna showed a good to high Ecological Quality Status (EcoQS) through time and at present. This indicates that environmental conditions have been and still are acceptable.

• Hess, Silvia; Alve, Elisabeth; Andersen, Thorbjørn J. & Joranger, Tore (2020). Defining ecological reference conditions in naturally stressed environments – How difficult is it? Marine Environmental Research. ISSN 0141-1136. 156. doi: 10.1016/j.marenvres.2020.104885. Fulltekst i vitenarkiv
• Deldicq, Noemie; Alve, Elisabeth; Schweizer, Magali; Asteman, Irina Polovodova; Hess, Silvia & Darling, Kate [Vis alle 7 forfattere av denne artikkelen] (2019). History of the introduction of a species resembling the benthic foraminifera nonionella stella in the oslofjord (Norway): Morphological, molecular and paleo-ecological evidences. Aquatic Invasions. ISSN 1798-6540. 14(2), s. 182–205. doi: 10.3391/ai.2019.14.2.03. Fulltekst i vitenarkiv Vis sammendrag

  Specimens resembling the benthic foraminifera Nonionella stella (Cushman and Moyer, 1930), a morphospecies originally described from the San Pedro Basin, California, USA, were observed for the first time in the Oslofjord (Norway) in 2012. This study investigates the Oslofjord Nonionella population in order to confirm its nonindigenous species (NIS) status and assess its introduction time. Morphological characterisation based on SEM imaging complemented by molecular identification using small subunit (SSU) rDNA sequencing and assessment of the recent past record (sediment core), were performed on material collected in the Oslofjord in 2016. Examination of the dead fauna showed that specimens resembling N. stella only appeared recently in the Oslofjord, confirming the NIS status of this population. Moreover, DNA results indicate that the Oslofjord specimens differ genetically from N. stella sampled in the Santa Barbara Basin (California USA). Hence, we propose to use the name Nonionella sp. T1 for the specimens sampled in the Oslofjord for the time being. In the southern part of the Skagerrak, specimens morphologically similar to Nonionella sp. T1 were reported as NIS in the Gullmar fjord (Sweden) in 2011 and in the Skagerrak in 2015. Molecular data indicate that the two populations from Gullmar- and Oslofjords are identical, based on their SSU rDNA sequences. In addition, analyses of foraminiferal dead assemblages suggest that the population from the Gullmar fjord settled prior to the Oslofjord population, i.e. ~ 1985 and about 2010, respectively. This implies that Nonionella sp. T1 may have been transported from Sweden to Norway by northward coastal currents.

• Alve, Elisabeth; Hess, Silvia; Bouchet, Vincent M P; Dolven, Jane K & Rygg, Brage (2018). Intercalibration of benthic foraminiferal and macrofaunal biotic indices: An example from the Norwegian Skagerrak coast (NE North Sea). Ecological Indicators. ISSN 1470-160X. 96, s. 107–115. doi: 10.1016/j.ecolind.2018.08.037. Fulltekst i vitenarkiv Vis sammendrag

  The present study illustrates how benthic macrofauna indices can be adapted to foraminifera through intercalibration of data from common sites. As an example of how benthic foraminifera can fit into governmental monitoring programs, we focus on Norwegian conditions by proposing a new foraminifera-based multimetric index, NQI_f. The index is an adaptation of the Norwegian Quality Index (NQI), which is an internationally intercalibrated macrofauna index. The study is based on published and new data for soft-bottom benthic foraminifera, macro invertebrates, and associated bottom water dissolved oxygen and sediment total organic carbon (TOC). Paired samples of foraminifera and macrofauna were collected at the same stations, at more or less the same time, along the Norwegian Skagerrak coast, NE North Sea. The intercalibration was based on linear regression and the EcoQS class boundary values for the foraminifera indices were derived from boundary values for the macrofauna indices defined by the Norwegian governmental guidelines. The correlations between foraminifera and macrofauna for the multimetric NQI and the diversity indices H′log2 and ES100 were all acceptable for intercalibration (according to the Water Framework Directive’s guidelines) but NQI showed the best correlation. Both foraminifera- and macrofauna-indices showed significant correlations with the bottom water dissolved oxygen concentration, and for some indices, with the TOC content in the sediment. Overall, the foraminifera and macrofauna indices reflected the environmental conditions similarly but at the most oxygen depleted stations only foraminifera were present. Based on the present findings and on previous studies which show a potential of fossil foraminifera to define in situ reference conditions, we recommend that foraminifera are accepted as a Biological Quality Element within the WFD.

• Duffield, CJ; Alve, Elisabeth; Andersen, N; Andersen, TJ; Hess, Silvia & Strohmeier, Tore (2017). Spatial and temporal organic carbon burial along a fjord to coast transect: A case study from Western Norway. The Holocene. ISSN 0959-6836. doi: 10.1177/0959683617690588. Fulltekst i vitenarkiv
• Duffield, Christopher James; Alve, Elisabeth; Andersen, Nils; Andersen, Thorbjørn J.; Hess, Silvia & Strohmeier, Tore (2017). Spatial and temporal organic carbon burial along a fjord to coast transect: A case study from Western Norway. The Holocene. ISSN 0959-6836. 27(9), s. 1325–1339. doi: 10.1177/0959683617690588. Fulltekst i vitenarkiv Vis sammendrag

  We investigated spatial and temporal changes in accumulation rate and source of organic carbon on a gradient along the Lysefjord and the more coastal Høgsfjord, Western Norway. This was achieved through analysis of total organic carbon and nitrogen content of sediment cores, which were radiometrically dated to the early 19th and 20th centuries for the Høgsfjord and Lysefjord, respectively. Benthic foraminifera (protists) were utilized to determine changes in organic carbon supply and Ecological Quality Status (EcoQS) by their accumulation rate (benthic foraminiferal accumulation rate (BFAR)), assemblage composition, species diversity, individual species responses and the composition of stable carbon isotopes of the tests (shells) of Cassidulina laevigata, Hyalinea balthica and Melonis barleeanus. Organic carbon accumulation rates were greatest closest to the river Lyse at the head of the Lysefjord (83–171 g C m−2 yr−1). The organic carbon at the head of the fjord is mainly terrestrial in origin, and this terrestrial influence becomes progressively less seaward. The δ13C in H. balthica tests as well as the benthic foraminiferal assemblage composition also showed a clear fjord to coast gradient. Organic carbon accumulation rates were lower and less variable at the seaward study sites (13–61 g C m−2 yr−1). We observe no temporal trend in organic carbon, carbon isotopes, EcoQS or foraminiferal assemblage composition in the Lysefjord. In contrast, in the Høgsfjord, there seems to have been an increase in organic carbon accumulation rates during the 1940s. Subsequent accumulation rates are stable. The foraminiferal assemblages in the surface sediments reflect a recent transition from good/moderate to moderate/bad EcoQS.

• Hess, Silvia & Nagy, Jenø (2017). New foraminiferal species from the Kapp Toscana Group (Carnian to Bathonian) of central Spitsbergen. I Kaminski, M.A. & Alegret, L. (Red.), Proceedings of the Ninth International Workshop on Agglutinated Foraminifera. Grzybowski Foundation. ISSN 9788394195618. s. 65–73. doi: 10.2307/1486047. Fulltekst i vitenarkiv
• Alve, Elisabeth; Korsun, Sergei; Schönfeld, Joachim; Dijkstra, Noortje; Golikova, Elena & Hess, Silvia [Vis alle 8 forfattere av denne artikkelen] (2016). Foram-AMBI: A sensitivity index based on benthic foraminiferal faunas from North-East Atlantic and Arctic fjords, continental shelves and slopes. Marine Micropaleontology. ISSN 0377-8398. 122, s. 1–12. doi: 10.1016/j.marmicro.2015.11.001. Fulltekst i vitenarkiv
• Duffield, Christopher James; Hess, Silvia; Norling, Karl & Alve, Elisabeth (2015). The response of Nonionella iridea and other benthic foraminifera to "fresh" organic matter enrichment and physical disturbance. Marine Micropaleontology. ISSN 0377-8398. 120, s. 20–30. doi: 10.1016/j.marmicro.2015.08.002. Fulltekst i vitenarkiv
• Hess, Silvia; Nagy, Jenø & Laursen, Gitte Vestergaard (2014). Benthic foraminifera from the lower jurassic transgressive mudstones of the south-western barents sea-a possible high-latitude expression of the global Pliensbachian-Toarcian turnover? Polar Research. ISSN 0800-0395. 33:20206. doi: 10.3402/polar.v33.20206. Fulltekst i vitenarkiv
• Hess, Silvia; Alve, Elisabeth & Reuss, Nina S. (2014). Benthic foraminiferal recovery in the Oslofjord (Norway): Responses to capping and re-oxygenation. Estuarine, Coastal and Shelf Science. ISSN 0272-7714. 147, s. 87–102. doi: 10.1016/j.ecss.2014.05.012. Fulltekst i vitenarkiv
• Hess, Silvia; Alve, Elisabeth; Trannum, Hilde Cecilie & Norling, Karl (2013). Benthic foraminiferal responses to water-based drill cuttings and natural sediment burial: Results from a mesocosm experiment. Marine Micropaleontology. ISSN 0377-8398. 101, s. 1–9. doi: 10.1016/j.marmicro.2013.03.004. Fulltekst i vitenarkiv Vis sammendrag

  Effects of burial by water-based drill cuttings and natural test sediment on living (stained) benthic foraminifera were investigated in a mesocosm experiment. After 193 days, the foraminiferal response in sediment covered with drill cuttings was compared to the response in sediment covered with defaunated natural test sediment. Increasing thickness of added material, independent of type of material, significantly reduced the benthic foraminiferal abundance and species richness. While most species managed to migrate through added sediments of up to 12 mm thickness, results indicate that a burial depth of 24 mm severely limits the migration capability of the foraminifera. Textularia earlandi and Bulimina marginata dominated the 0–1 cm of sediment (including added material) in most mesocosms but the former was most resistant to maximum burial (24 mm). The physical disturbance caused by the burial triggered reproduction in surviving populations of B. marginata and Nonionellina labradorica. Addition of water-based drill cuttings and defaunated natural test sediments impacted the microhabitat of N. labradorica differently. Stainforthia fusiformis seems to be the species most tolerant to the water-based drill cuttings. Results indicate that the foraminiferal faunal composition respond differently to the two different materials added, even if only agglutinated forms are considered. This agrees with earlier macrofaunal results from the same experiment which indicate that the water-based drill cuttings represent an additional stress factor for the benthic community.

Se alle arbeider i NVA

• Barras, Christine; Bouchet, Vincent; Hess, Silvia; Hyams-Kaphzan, Orit; Martinez-Colon, Michael & Polovodova-Asteman, Irina (2024). FOBIMO Workshop - The reboot. Fulltekst i vitenarkiv
• Fransson, Agneta; Bluhm, Bodil Annikki Ulla Barbro; Kohlbach, Doreen; Assmy, Philipp Kurt Wolf; Bratbak, Gunnar & Amargant, Marti [Vis alle 37 forfattere av denne artikkelen] (2024). Nansen vs. Amundsen Basin: Constrasting physico-chemical properties and biota composition to inform management. Fulltekst i vitenarkiv
• Hess, Silvia & Dauvi, Adriana Amundsen (2023). Mikrofossiler avslører Oslofjordens miljøtilstand. Fulltekst i vitenarkiv
• Asteman, Irina Polovodova; Alve, Elisabeth; Dolven, Jane; Eliassen, Nicole; Ferraro, Mattia & Hess, Silvia [Vis alle 18 forfattere av denne artikkelen] (2023). Spreading of an alien benthic foraminifer in the North Sea: a reason to be worried? Fulltekst i vitenarkiv Vis sammendrag

  In the Skagerrak-Kattegat (eastern North Sea), the alien benthic foraminifer Nonionella sp. T1 (previously referred to as “Nonionella stella”) was reported for the first time in 2011 and 2012 in the Swedish and southern Norwegian fjords, respectively. Based on dated sediment cores its first occurrence can be traced back to the 1980s in the Gullmar Fjord, to the 2000s in the Öresund and to 2010 in the Oslofjord. Since then, Nonionella sp T1 has spread all over the Kattegat and coastal Skagerrak, according to sampling campaigns performed between 2016 and 2022. The species is now highly abundant in the entire Kattegat, including the Öresund, as well as in fjord mouths of the seasonally hypoxic Gullmar Fjord, the oxic Hakefjord and the long-term polluted Idefjord as demonstrated by molecular and morphospecies data. At the same time, Nonionella sp T1 is rare to absent in the Baltic Sea, Skagerrak deep basin and in deep fjords of western and northern Norway. This study shows some preliminary results on the species’ present distribution in the study area and raises questions about the driving factors and potential effects on the local biodiversity.

• Hess, Silvia; Alve, Elisabeth & Helland, Aud (2023). Retrospective benthic foraminiferal community studies: a sensitive method to determine early environmental changes. Fulltekst i vitenarkiv
• Freitas, Thaise Ricardo de; Hess, Silvia; Renaud, Paul Eric & Alve, Elisabeth (2023). Spatio-temporal distribution patterns of benthic foraminifera in the northern Barents Sea. Fulltekst i vitenarkiv
• Ziegler, Amanda; Freitas, Thaise Ricardo de; Altenburger, Andreas; Alve, Elisabeth; Bluhm, Bodil & Bodur, Yasemin V. [Vis alle 17 forfattere av denne artikkelen] (2022). Lack of (or weak) seasonality in Barents sea and Nansen Basin sediments and biota? A preliminary assessment. Fulltekst i vitenarkiv
• Freitas, Thaise Ricardo de; Hess, Silvia; Renaud, Paul Eric & Alve, Elisabeth (2022). Seasonal variability on living benthic foraminiferal biodiversity in the northern Barents Sea: preliminary results. Fulltekst i vitenarkiv
• Freitas, Thaise Ricardo de; Hess, Silvia; Renaud, Paul Eric & Alve, Elisabeth (2022). Benthic foraminiferal biodiversity in the northern Barents Sea: preliminary results. Fulltekst i vitenarkiv
• Freitas, Thaise Ricardo de; Alve, Elisabeth; Hess, Silvia & Renaud, Paul Eric (2021). Drivers of organic carbon distribution and accumulation in the Northern Barents Sea. Fulltekst i vitenarkiv
• Hess, Silvia; Sjetne, Lars Birkeland & Alve, Elisabeth (2020). Impact of aquaculture activity on the benthic environment - A stratigraphic study from Hardangerfjorden (SW Norway). Fulltekst i vitenarkiv
• Hess, Silvia; Alve, Elisabeth & Dolven, Jane Karine Lønne (2019). Bruk av foraminiferer som miljøindikator for vannkvalitet og levevilkår på sjøbunnen i Indre Oslofjord - Har dypvanssfornyelsen og bedrede oksygenforhold i Bunnefjorden i 2018 hatt effekt på foraminiferfaunaen på sjøbunnen? Fulltekst i vitenarkiv
• Hess, Silvia; Sjetne, Lars Birkeland & Alve, Elisabeth (2018). Does aquaculture activity have an impact on the benthic environment? - A study from Hardangerfjorden (SW Norway). Fulltekst i vitenarkiv
• Deldicq, Noémie; Alve, Elisabeth; Schweizer, Magali; Asteman, Irina Polovodova; Hess, Silvia & Darling, Kate [Vis alle 7 forfattere av denne artikkelen] (2018). Is the foraminiferal species resembling Nonionella stella a non-indigenous species (NIS) in the Oslofjord (Norway)? Fulltekst i vitenarkiv
• Hess, Silvia; Alve, Elisabeth; Joranger, Tore & Oen, Amy M P (2016). Defining pre-industrial ecological status (reference conditions) in heavily polluted shallow harbor areas – a case study from SE Norway. Fulltekst i vitenarkiv
• Hess, Silvia; Guilini, Katja; Michiels, Diego; Torper, Magnhild; Alve, Elisabeth & Sweetman, Andrew Kvassnes [Vis alle 7 forfattere av denne artikkelen] (2016). Meiofauna monitoring in two different fjord systems of the Norwegian west coast: Does the mass appearance of Periphylla periphylla (a deep-sea jellyfish) have an impact on the benthic community? Fulltekst i vitenarkiv
• Hess, Silvia (2016). Benthic foraminifera as indicators of environmental changes in Norwegian fjords. Fulltekst i vitenarkiv
• Duffield, Christopher James; Alve, Elisabeth; Andersen, Nils; Andersen, Thorbjørn J.; Hess, Silvia & Strohmeier, Tore (2015). Benthic foraminifera and organic carbon along a fjord to coast transect in western, Norway. Fulltekst i vitenarkiv
• Korsun, Sergei; Alve, Elisabeth; Golikova, Elena; Hess, Silvia; Husum, Katrine & Panieri, Giuliana [Vis alle 7 forfattere av denne artikkelen] (2014). Does AMBI, a commonly used macrofauna-based ecological monitoring measure, work for benthic Foraminifera? The Fobimo-NE Atlantic group. Fulltekst i vitenarkiv
• Hess, Silvia; Nagy, Jenø & Laursen, G.V. (2013). Benthic foraminiferal assemblages in Early Jurassic deposits of the south-western Barents Sea. Fulltekst i vitenarkiv
• Alve, Elisabeth; Bouchet, Vincent; Dolven, Jane Karine Lønne; Hess, Silvia; Magnusson, Jan & Oug, Eivind [Vis alle 8 forfattere av denne artikkelen] (2013). Marine soft-bottom bio-monitoring strategies: Can microfossils make a difference? Fulltekst i vitenarkiv
• Hess, Silvia; Nagy, Jenø & Laursen, G.V. (2013). Benthic foraminiferal assemblages in Early Jurassic deposits of the south-western Barents Sea. I Nakrem, Hans Arne & haukdal, gunn (Red.), NGF Vinterkonferansen 2013. Oslo, 8-20. January, 2013. NGF Abstracts and Proceedings of the Geological Society of Norway 1 (2013). Norsk Geologisk Forening. ISSN 9788292394786. s. 58–58. Fulltekst i vitenarkiv
• Bouchet, Vincent; Hess, Silvia; Dolven, Jane Karine Lønne & Alve, Elisabeth (2012). The use of fossil benthic foraminifera to define reference conditions for present-day marine waters. Geophysical Research Abstracts. ISSN 1029-7006. 14. Fulltekst i vitenarkiv
• Bouchet, Vincent; Hess, Silvia; Dolven, Jane Karine Lønne; Alve, Elisabeth & Telford, Richard J. (2012). Benthic foraminifera as indicators of ecological quality of coastal marine systems. Fulltekst i vitenarkiv
• Hess, Silvia; Nagy, Jenø & Laursen, Gitte Vestergaard (2012). Paleoenvironmental interpretations of Early to Middle Jurassic deposits of the southwestern Barents Sea based on benthic foraminiferal assemblages. Fulltekst i vitenarkiv
• Ludvigsen, Martin; Assmy, Philipp; Adams, Matthew James Samuel; Arumi, Marti A.; Mo-Bjørkelund, Tore & Bodur, Yasemin V. [Vis alle 36 forfattere av denne artikkelen] (2022). Seasonal cruise Q2 2021: Cruise Report. Septentrio Academic Publishing. Fulltekst i vitenarkiv Vis sammendrag

  The spring season was the target for the Nansen Legacy cruise organized in late April and first half of May 2021 following the transect defined for this series of cruises to capture the variations of the year sampling physical, biological and chemical conditions in the ice and the sea. The transect went through both open water and ice. Seven process stations were visited (P1 through P7) together with smaller NLEG stations according to the program for the seasonal investigations. The first station (P1) was in open waters, while the remaining six main station had ice coverage of varying degree. Each of the process stations lasted 24 hours or more to allow a full diurnal cycle. Sampling included ice physics, ice samples, phytoplankton, zooplankton, marine chemistry and eco toxicology using acoustic, optical and robotics methods together with lab analyses of physical samples. Remote sensing data were also matched with in situ observations of both sea and ice conditions.

• Hess, Silvia; Alve, Elisabeth & Helland, Aud (2021). E 16 og Vossebanen, Arna-Stanghelle. Miljøforholdene i Sørfjorden og Veafjorden, Vestland, dagens og tidligere tiders tilstand. Statens vegvesen, rapport UAS-01-Q-00029. Fulltekst i vitenarkiv
• Dolven, Jane Karine Lønne; Hess, Silvia; Hylland, Ketil & Alve, Elisabeth (2018). Foraminiferer som miljøindikator for vannkvalitet og levevilkår på sjøbunnen i Indre Oslofjord. Fagrådet for vann- og avløpstekninsk samarbeid i indre Oslofjord. Fulltekst i vitenarkiv Vis sammendrag

  Tidligere undersøkelser i Indre Oslofjord har vist at bunnlevende foraminiferer (meiofauna) reflekterer miljøforholdene de lever i og kan dermed brukes til å gi informasjon om økologisk tilstand og levevilkår på sjøbunnen. For å kartlegge dagens tilstand i Indre Oslofjord og like utenfor Drøbaksterskelen, og å vurdere utviklingstrenden i fjordsystemet, ble det i oktober 2017 samlet inn bunnsedimenter på 12 stasjoner. Bunnsedimentene ble undersøkt med hensyn på levende foraminiferfaunaer, kornfordeling, total organisk karbon og C/N-forhold. I tillegg ble det gjennomført hydrografiske målinger (temperatur, salinitet og oksygen) gjennom vannsøylen på hver av stasjonene. Resultatene viser at den økologiske tilstanden (nEQR) er «svært god» (tilstandsklasse I) utenfor Drøbaksterskelen og i sydlige deler av Vestfjorden. Deretter forringes tilstanden gradvis innover i fjorden til Bunnefjorden hvor den økologiske tilstanden er «svært dårlig» (V). I to sub-bassenger avviker tilstanden fra tilstanden i deres respektive hovedbasseng: 1) Det delvis «isolerte» Steilenebassenget (St 2) i Vestfjorden hvor forholdene er dårligere enn i Vestfjorden forøvrig, dvs. tilstandsklasse IV («dårlig») og 2) den nordøstre del av Bekkelagsbassenget (RC5 og RC9) hvor tilstanden er i klasse II («god»), dvs. bedre enn nærliggende stasjoner. Sistnevnte skyldes forbedringstiltak igangsatt med flytting av utløpsledningen fra Bekkelaget renseanlegg til dypere vann tidlig på 2000-tallet. I de indre deler av fjorden er det et stort avvik mellom dagens økologiske tilstand («svært dårlig») og naturtilstanden («svært god») som tidligere er beregnet basert på fossile foraminiferfaunaer i daterte sedimentkjerner. I ytre deler av Vestfjorden og utenfor Drøbaksterskelen samsvarer nåværende tilstand godt med naturtilstanden. Økt hyppighet av den opportunistiske arten Stainforthia fusiformis utenfor Drøbaksterskelen peker i retning av økt eutrofiering i senere år. En invaderende art, Nonionella stella, som først ble registrert i Indre Oslofjord i 2012 er nå til stede og til dels hyppig på alle stasjoner, bortsett fra de mest oksygenfattige Bunnefjordstasjonene. Det er generelt høyt organisk karbon (TOC)-innhold («svært dårlig» tilstand) i overflatesedimentene i Indre Oslofjord, og innholdet korrelerer godt med både diversitetsindeksene (H’log2 og ES100) og den sammensatte indeksen NQI. Unntaket er representert ved en stasjon i Bekkelagsbassenget (RC5), som ble kunstig tildekket med ren marin leire i 2007. Korrelasjonen mellom foraminiferdata og målte oksygenkonsentrasjoner i bunnvannet er svært god. Faunasammensetningen (klyngeanalysen) for alle stasjonene støtter opp under dette. Samlet gir dette en sterk indikasjon på at oksygen er en av de viktigste faktorene som styrer sammensetningen av foraminiferfaunaene i Indre Oslofjord. Variabiliteten i foraminiferfaunen er undersøkt for en sterkt belastet stasjon (St 2) og en referansestasjon (Im4x). Analyser av artsdiversitet og jevnhet basert på 10 replikater fra hver stasjon viser at det ikke er signifikant endring for de ulike indeksene ved analyse av flere enn tre replikater fra samme stasjon. Variabiliteten mellom replikatene fører imidlertid til at bruk av færre enn fire replikater per stasjon kan medføre feilklassifisering. Det anbefales å benytte minst fire replikate prøver ved sammenligning av to eller flere lokaliteter siden det gir vesentlig økt teststyrke (mulighet til å fastslå korrekt klasse og å skille mellom stasjoner).

• Alve, Elisabeth; Hess, Silvia; Sørlie, Carsten; Klootwijk, Anouk Tosca & Dolven, Jane Karine Lønne (2018). Akvakultur og naturtilstand i en Nordnorsk fjord: har miljøstatus forandret seg? 7Letras. Fulltekst i vitenarkiv
• Pedersen, Are; Alve, Elisabeth; Alvestad, Tom; Borgersen, Gunhild; Dolven, Jane & Gundersen, Hege [Vis alle 11 forfattere av denne artikkelen] (2016). Bløtbunnsfauna som indikator for miljøtilstand i kystvann. Ekspertvurderinger og forslag til nye klassegrenser og metodikk. Miljødirektoratet. Fulltekst i vitenarkiv
• Hess, Silvia & Alve, Elisabeth (2014). Undersøkelser av den historiske oksygenutviklingen og naturtilstanden i Horten Indre Havn. 7Letras. ISSN 9788291885445. Fulltekst i vitenarkiv

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