Dag Olav Hessen

• Lindholm, Markus; Eie, Martin Espedal; Hessen, Dag Olav; Johansen, Joachim Tørud; Weiby, Kristoffer & Thaulow, Jens (2018). Effects of water browning on freshwater biodiversity: the case of the predatory phantom midge Chaoborus nyblaei. Hydrobiologia.  ISSN 0018-8158.  813(1), s 33- 40 . doi: 10.1007/s10750-017-3503-x
• Walseng, Bjørn; Jensen, Thomas Correll; Dimante-Deimantovica, Inta; Christoffersen, Kirsten Seestern; Chertoprud, Mikhail; Chertoprud, Elena; Novichkova, Anna & Hessen, Dag Olav (2018). Freshwater diversity in Svalbard: providing baseline data for ecosystems in change. Polar Biology.  ISSN 0722-4060.  s 1- 11 . doi: 10.1007/s00300-018-2340-3
• Wolf, Raoul; Thrane, Jan-Erik; Hessen, Dag Olav & Andersen, Tom (2018). Modelling ROS formation in boreal lakes from interactions between dissolved organic matter and absorbed solar photon flux. Water Research.  ISSN 0043-1354.  132, s 331- 339 . doi: 10.1016/j.watres.2018.01.025 Full text in Research Archive.
• Alfsnes, Kristian; Leinaas, Hans Petter & Hessen, Dag Olav (2017). Genome size in arthropods; different roles of phylogeny, habitat and life history in insects and crustaceans. Ecology and Evolution.  ISSN 2045-7758.  7(15), s 5939- 5947 . doi: 10.1002/ece3.3163 Full text in Research Archive.
• Anderson, Thomas R.; Hessen, Dag Olav; Boersma, Maarten; Urabe, Jotaro & Mayor, Daniel J. (2017). Will invertebrates require increasingly carbon-rich food in a warming world?. American Naturalist.  ISSN 0003-0147.  190(6), s 725- 742 . doi: 10.1086/694122
• Guignard, Maïté S.; Leitch, Andrew R.; Aquisti, Claudia; Eitzaguirre, Christophe; Elser, James J.; Hessen, Dag Olav; Jeyasingh, Punidan D.; Neiman, Maurine; Richardson, Alan E.; Soltis, Pamela S.; Soltis, Douglas E.; Stevens, Carly J.; Trimmer, Mark; Weider, Lawrence J.; Woodward, Guy & Leitch, Ilia J. (2017). Impacts of nitrogen and phosphorus: From genomes to natural ecosystems and agriculture. Frontiers in Ecology and Evolution.  ISSN 2296-701X.  5, s 1- 9 . doi: 10.3389/fevo.2017.00070
• Hessen, Dag Olav; Andersen, Tom; Tominaga, Koji & Finstad, Anders Gravbrøt (2017). When soft waters becomes softer; drivers of critically low levels of Ca in Norwegian lakes. Limnology and Oceanography.  ISSN 0024-3590.  62(1), s 289- 298 . doi: 10.1002/lno.10394 Full text in Research Archive.
• Hessen, Dag Olav; Hafslund, Ola Tobias; Andersen, Tom; Broch, Catharina; Shala, Nita Kaupang & Wojewodzic, Marcin (2017). Changes in stoichiometry, cellular RNA, and alkaline phosphatase activity of chlamydomonas in response to temperature and nutrients. Frontiers in Microbiology.  ISSN 1664-302X.  8(18), s 1- 8 . doi: 10.3389/fmicb.2017.00018
• Hessen, Dag Olav; Håll, Johnny Peter; Thrane, Jan-Erik & Andersen, Tom (2017). Coupling dissolved organic carbon, CO2 and productivity in boreal lakes. Freshwater Biology.  ISSN 0046-5070.  62(5), s 945- 953 . doi: 10.1111/fwb.12914
• Hessen, Dag Olav; Tombre, Ingunn; van Geest, Gerben & Alfsnes, Kristian (2017). Global change and ecosystem connectivity: how geese link fields of central Europe to eutrophication of Arctic freshwaters. Ambio.  ISSN 0044-7447.  46(1), s 40- 47 . doi: 10.1007/s13280-016-0802-9 Full text in Research Archive. Show summary

  arctic connectivity eutrophication migration

• Neiman, Maurine; Beaton, Margaret J.; Hessen, Dag Olav; Jeyasingh, Punidan D. & Weider, Lawrence J. (2017). Endopolyploidy as a potential driver of animal ecology and evolution. Biological Reviews.  ISSN 1464-7931.  92(1), s 234- 247 . doi: 10.1111/brv.12226 Full text in Research Archive.
• Skau, Lars Fredrik; Andersen, Tom; Thrane, Jan-Erik & Hessen, Dag Olav (2017). Growth, stoichiometry and cell size; temperature and nutrient responses in haptophytes. PeerJ.  ISSN 2167-8359.  5 . doi: 10.7717/peerj.3743 Full text in Research Archive.
• Spears, Bryan; Futter, Martyn N.; Jeppesen, Erik; Huser, Brian J; Ives, Stephen; Davidson, Thomas A; Adrian, Rita; Angeler, David G.; Burthe, Sarah J; Carvalho, Laurence; Daunt, Francis; Gsell, Alena S; Hessen, Dag Olav; Janssen, Annette B G; MacKay, Eleanor B; May, Linda; Moorhouse, Heather; Olsen, Saara; Søndergaard, Martin; Woods, Helen & Thackeray, Stephen J. (2017). Ecological resilience in lakes and the conjunction fallacy. Nature Ecology & Evolution.  ISSN 2397-334X.  1(11), s 1616- 1624 . doi: 10.1038/s41559-017-0333-1 Full text in Research Archive.
• Thrane, Jan-Erik; Hessen, Dag Olav & Andersen, Tom (2017). Plasticity in algal stoichiometry: Experimental evidence of a temperature-induced shift in optimal supply N:P ratio. Limnology and Oceanography.  ISSN 0024-3590.  62(4), s 1346- 1354 . doi: 10.1002/lno.10500
• Wolf, Raoul; Andersen, Tom; Hessen, Dag Olav & Hylland, Ketil (2017). The influence of dissolved organic carbon and ultraviolet radiation on the genomic integrity of Daphnia magna. Functional Ecology.  ISSN 0269-8463.  31(4), s 848- 855 . doi: 10.1111/1365-2435.12730 Full text in Research Archive.
• Adrian, Rita & Hessen, Dag Olav (2016). Environmental Impacts—Lake Ecosystems, In Markus Quante & Franciscus Colijn (ed.),  North Sea Region Climate Change Assessment.  Springer Publishing Company.  ISBN 978-3-319-39743-6.  Kapittel 10.  s 315 - 340
• Alfsnes, Kristian; Hobæk, Anders; Weider, Lawrence J. & Hessen, Dag O. (2016). Birds, nutrients, and climate change: mtDNA haplotype diversity of Arctic Daphnia on Svalbard revisited. Polar Biology.  ISSN 0722-4060.  39(8), s 1425- 1437 . doi: 10.1007/s00300-015-1868-8
• de Wit, Heleen A.; Valinia, Salar; Weyhenmeyer, Gesa A; Futter, Martyn N.; Kortelainen, Pirkko; Austnes, Kari; Hessen, Dag O; Raike, Antti; Laudon, Hjalmar & Vournenmaa, Jussi (2016). Current Browning of Surface Waters Will Be Further Promoted by Wetter Climate. Environmental Science and Technology Letters.  ISSN 2328-8930.  3(12), s 430- 435 . doi: 10.1021/acs.estlett.6b00396 Full text in Research Archive.
• Finstad, Anders Gravbrøt; Andersen, Tom; Larsen, Søren; Tominaga, Koji; Blumentrath, Stefan; de Wit, Heleen A.; Tømmervik, Hans & Hessen, Dag Olav (2016). From greening to browning: Catchment vegetation development and reduced S-deposition promote organic carbon load on decadal time scales in Nordic lakes. Scientific Reports.  ISSN 2045-2322.  6 . doi: 10.1038/srep31944 Full text in Research Archive. Show summary

  Increased concentrations of dissolved organic carbon (DOC), often labelled “browning”, is a current trend in northern, particularly boreal, freshwaters. The browning has been attributed to the recent reduction in sulphate (S) deposition during the last 2 to 3 decades. Over the last century, climate and land use change have also caused an increasing trend in vegetation cover (“greening”), and this terrestrially fixed carbon represents another potential source for export of organic carbon to lakes and rivers. The impact of this greening on the observed browning of lakes and rivers on decadal time scales remains poorly investigated, however. Here, we explore time-series both on water chemistry and catchment vegetation cover (using NDVI as proxy) from 70 Norwegian lakes and catchments over a 30-year period. We show that the increase in terrestrial vegetation as well as temperature and runoff significantly adds to the reduced SO4-deposition as a driver of freshwater DOC concentration. Over extended periods (centuries), climate mediated changes in vegetation cover may cause major browning of northern surface waters, with severe impact on ecosystem productivity and functioning.

• Hanevik, Hans Ivar; Hessen, Dag Olav; Sunde, Arne & Breivik, Jarle (2016). Can IVF influence human evolution?. Human Reproduction.  ISSN 0268-1161.  31(7), s 1397- 1402 . doi: 10.1093/humrep/dew089
• Hessen, Dag Olav (2016). Seleksjon ved konsekvenser – og konsekvensene av seleksjon. Norsk Tidsskrift for Atferdsanalyse.  ISSN 0809-781X.  43, s 51- 55
• Leinaas, Hans Petter; Jalal, Marwa; Gabrielsen, Tove M. & Hessen, Dag Olav (2016). Inter- and intraspecific variation in body- and genome size in calanoid copepods from temperate and arctic waters. Ecology and Evolution.  ISSN 2045-7758.  6(16), s 5585- 5595 . doi: 10.1002/ece3.2302 Full text in Research Archive.
• Lindholm, Markus; Wolf, Raoul; Finstad, Anders & Hessen, Dag O (2016). Water browning mediates predatory decimation of the Arctic fairy shrimp Branchinecta paludosa. Freshwater Biology.  ISSN 0046-5070.  61(3), s 340- 347 . doi: 10.1111/fwb.12712
• Thrane, Jan-Erik; Hessen, Dag Olav & Andersen, Tom (2016). The impact of irradiance on optimal and cellular nitrogen to phosphorus ratios in phytoplankton. Ecology Letters.  ISSN 1461-023X.  19(8), s 880- 888 . doi: 10.1111/ele.12623
• Feng, Jianfeng; Durant, Joel Marcel; Stige, Leif Christian; Hessen, Dag Olav; Hjermann, Dag Øystein; Zhu, Lin; Llope, Marcos & Stenseth, Nils Christian (2015). Contrasting correlation patterns between environmental factors and chlorophyll levels in the global ocean. Global Biogeochemical Cycles.  ISSN 0886-6236.  29(12), s 2095- 2107 . doi: 10.1002/2015GB005216
• Hessen, Dag Olav (2015). Noncoding DNA as a Phenotypic Driver. Evolutionary biology.  ISSN 0071-3260.  42, s 427- 431 . doi: 10.1007/s11692-015-9335-6
• Jalal, Marwa; Andersen, Tom & Hessen, Dag Olav (2015). Temperature and developmental responses of body and cell size in Drosophila; effects of polyploidy and genome configuration. Journal of Thermal Biology.  ISSN 0306-4565.  51, s 1- 14 . doi: 10.1016/j.jtherbio.2015.02.011
• Jeyansingh, Pinidian; Chowdhury, Priyanka; Wojewodzic, Marcin; Frisch, Dagmar; Hessen, Dag Olav & Weider, Lawrence J. (2015). Phosphorus use and excretion varies with ploidy level in Daphnia. Journal of Plankton Research.  ISSN 0142-7873.  37, s 1210- 1217 . doi: 10.1093/plankt/fbv095
• Lindholm, Markus; Hessen, Dag Olav; Færøvig, Per-Johan; Rognerud, Bjørg; Andersen, Tom & Stordal, Frode (2015). Is distribution of cold stenotherms constrained by temperature? The case of the Arctic fairy shrimp (Branchinecta paludosa O.F. Müller 1788). Journal of Thermal Biology.  ISSN 0306-4565.  53, s 46- 52 . doi: 10.1016/j.jtherbio.2015.08.005
• Walseng, Bjørn; Andersen, Tom & Hessen, Dag Olav (2015). Higher zooplankton species richness associated with an invertebrate top predator. Freshwater Biology.  ISSN 0046-5070.  60(5), s 903- 910 . doi: 10.1111/fwb.12543 Show summary

  1. A dataset of 1735 Norwegian lakes, spanning a wide range of geographical, physical, chemical and biological properties, was analysed to assess the role of the top invertebrate predator, Bythotrephes longimanus, on the crustacean species richness and community structure. 2. Bythotrephes was associated with a 25.5% increase in mean richness of other zooplankton species, and this effect could not be related to confounding factors. Based on presence–absence data, community composition did not differ significantly between lakes with and without this top predator. 3. Neither fish predation nor lake area, altitude, and geographical or physicochemical parameters offer any obvious impact on the observed diversity patterns. We suggest that Bythotrephes facilitates species richness by reducing the abundance of species controlling subdominant species. 4. This pattern of increased diversity offers an interesting contrast to North American lakes recently invaded by Bythotrephes, where species richness typically has decreased, suggesting different shortterm and long-term effects of predatory invaders. Keywords: diversity, lakes, predator, richness, zooplankton

• Yang, Hong; Andersen, Tom; Dörsch, Peter; Tominaga, Koji; Thrane, Jan-Erik & Hessen, Dag Olav (2015). Greenhouse gas metabolism in Nordic boreal lakes. Biogeochemistry.  ISSN 0168-2563.  126(1-2), s 211- 225 . doi: 10.1007/s10533-015-0154-8 Full text in Research Archive. Show summary

  Boreal lakes are important net sources of greenhouse gases (GHGs). In this study we analyzed concentrations of CO2, CH4, N2O as well as O2, N2 and argon (Ar) from the epilimnion of 75 boreal lakes covering gradients in total organic carbon (TOC), phosphorus (P) and nitrogen (N) deposition. The Ar-corrected gas saturation deficit was used as a proxy of net metabolic changes from spring overturn to mid-summer sampling (all lakes were dimictic). Emission fluxes were calculated for CO2, CH4 and N2O based on partial pressure, water temperature and wind speed. Gas concentrations, actual and Ar-corrected, were related to lake specific properties. TOC was the main predictor of CO2 concentrations and fluxes, followed by total P, while total P and chlorophyll a governed CH4 concentrations and fluxes. Nitrogen (NO3 - or total N) were key predictors of N2O concentrations and fluxes, followed by total P. Altitude, area and depth were not strong predictors of CO2, CH4 and N2O concentrations and fluxes, likely because only lakes with an area of [1 km2 were included. CO2 molar concentrations were negatively correlated with O2 concentrations, while the slope of CO2 concentration to Ar corrected O2 deficit was 1.039. Together with the poor correlation between area-specific primary production and CO2 as well as O2, this suggests that these gases are mostly affected by catabolic processes and probably photo-oxidation in these nutrient-poor, boreal lakes investigated in this study. Increasing inputs of TOC (i.e. lake ‘‘browning’’) is likely to promote the net heterotrophy and hence emissions of all GHGs, while elevated N deposition in particular may cause elevated emissions of N2O.

• Feng, Jianfeng; Stige, Leif Christian; Durant, Joel Marcel; Hessen, Dag Olav; Zhu, Lin; Hjermann, Dag Øystein; Llope, Marcos & Stenseth, Nils Christian (2014). Large-scale season-dependent effects of temperature and zooplankton on phytoplankton in the North Atlantic. Marine Ecology Progress Series.  ISSN 0171-8630.  502, s 25- 37 . doi: 10.3354/meps10724
• Finstad, Anders Gravbrøt; Helland, Ingeborg Palm; Ugedal, Ola; Hesthagen, Trygve H. & Hessen, Dag Olav (2014). Unimodal response of fish yield to dissolved organic carbon. Ecology Letters.  ISSN 1461-023X.  17(1), s 36- 43 . doi: 10.1111/ele.12201 Full text in Research Archive.
• Frigstad, Helene; Andersen, Tom; Bellerby, Richard; Silyakova, Anna & Hessen, Dag Olav (2014). Variation in the seston C:N ratio of the Arctic Ocean and pan-Arctic shelves. Journal of Marine Systems.  ISSN 0924-7963.  129, s 214- 223 . doi: 10.1016/j.jmarsys.2013.06.004
• Hessen, Dag Olav & Kaartvedt, Stein (2014). Top-down cascades in lakes and oceans: Different perspectives but same story?. Journal of Plankton Research.  ISSN 0142-7873.  36(4), s 914- 924 . doi: 10.1093/plankt/fbu040
• Jalal, Marwa; Shala, Nita Kaupang; Wojewodzic, Marcin; Andersen, Tom; Hessen, Dag Olav & Schwarzacher, T (2014). Multigenerational genomic responses to dietary phosphorus and temperature in Daphnia. Genome.  ISSN 0831-2796.  57(8), s 439- 448 . doi: 10.1139/gen-2014-0047
• Reusch, Marianne & Hessen, Dag Olav (2014). Friluftslivets høstingsrett – I biologisk og juridisk perspektiv. Nordisk miljörättslig tidskrift.  ISSN 2000-4273.  2013(2), s 67- 84
• Skurdal, Jostein; Johnsen, Stein Ivar; Garnås, Erik; Hessen, Dag Olav & Qvenild, Tore (2014). Hva har vi lært etter 35 års overvåking av ferskvannskreps i Steinsfjorden?. Vann.  ISSN 0042-2592.  (1), s 6- 16
• Thrane, Jan-Erik; Hessen, Dag Olav & Andersen, Tom (2014). The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity. Ecosystems.  ISSN 1432-9840.  17(6), s 1040- 1052 . doi: 10.1007/s10021-014-9776-2
• Wilson, David S. & Hessen, Dag Olav (2014). Blueprint for the Global Village. Cliodynamics.  ISSN 2373-7530.  5, s 123- 157
• Anderson, Thomas R.; Hessen, Dag Olav; Mitra, Aditee; Mayor, Daniel J. & Yool, Andrew (2013). Sensitivity of secondary production and export flux to choice of trophic transfer formulation in marine ecosystem models. Journal of Marine Systems.  ISSN 0924-7963.  125, s 41- 53 . doi: 10.1016/j.jmarsys.2012.09.008
• Aubert, Anais; Svensen, Camilla; Hessen, Dag Olav & Tamelander, Tobias (2013). CNP stoichiometry of a lipid-synthesising zooplankton, Calanus finmarchicus, from winter to spring bloom in a sub-Arctic sound. Journal of Marine Systems.  ISSN 0924-7963.  111, s 19- 28 . doi: 10.1016/j.jmarsys.2012.09.004
• Frigstad, Helene; Andersen, Tom; Hessen, Dag Olav; Jeansson, Emil; Skogen, Morten D.; Naustvoll, Lars Johan; Miles, Martin W.; Johannessen, Truls & Bellerby, Richard (2013). Long-term trends in carbon, nutrients and stoichiometry in Norwegian coastal waters: Evidence of a regime shift. Progress in Oceanography.  ISSN 0079-6611.  111, s 113- 124 . doi: 10.1016/j.pocean.2013.01.006 Show summary

  A 20-year time series from the Norwegian Coastal Current was explored to examine the effects of advected nutrient supply from the southern North Sea and of large-scale climate variability on hydrography, nutrients and particulate organic matter (seston), focusing on trends in the January to April period in the upper layers (0–30 m). The interannual variability in hydrography, nutrients and seston was correlated with the NAO index, mostly through the inflow of nutrient-rich waters from the southern North Sea. There was a long-term decrease in nutrient concentrations, which according to a water mass analysis followed a reduction in nutrients advected from the German Bight and southern North Sea. The concentrations of carbon and nitrogen in seston, dissolved organic nitrogen and the estimated fraction of non-autotrophic material increased significantly and non-linearly through a sharp transition between 1998 and 2000, and have remained at this level since. Humic coagulation was suggested as the mechanism behind the increase in the non-autotrophic fraction of seston, which could be connected with the reported “darkening” of the coastal Skagerrak and Baltic Sea. Concurrent with the thresholds in suspended material, a decimation of the sugar kelp forest and recruitment failure of key carnivorous fish was reported for the same region, suggesting that a regime shift took place in the early 2000s in the coastal waters of the Norwegian Skagerrak. Our data suggests that the effects of increased freshwater runoff, especially the increased inputs of terrestrial-derived, humic material, could play an important role in the observed, coastal responses.

• Hessen, Dag Olav (2013). Inorganic Nitrogen Deposition and Its Impacts on N:P-Ratios and Lake Productivity. Water.  ISSN 2073-4441.  5(2), s 327- 341 . doi: 10.3390/w5020327
• Hessen, Dag Olav; Daufresne, Martin & Leinaas, Hans Petter (2013). Temperature-size relations from the cellular-genomic perspective. Biological Reviews.  ISSN 1464-7931.  88(2), s 476- 489 . doi: 10.1111/brv.12006
• Hessen, Dag Olav; Elser, James J.; Sterner, Robert W. & Urabe, Jotaro (2013). Ecological stoichiometry: An elementary approach using basic principles. Limnology and Oceanography.  ISSN 0024-3590.  58(6), s 2219- 2236 . doi: 10.4319/lo.2013.58.6.2219
• Jalal, Marwa; Wojewodzic, Marcin; Laane, Carl Morten Motzfeldt & Hessen, Dag Olav (2013). Large Daphnia at lower temperature: a role for cell size and genome configuration?. Genome.  ISSN 0831-2796.  56, s 511- 519 . doi: 10.1139/gen-2013-0004
• Kelly, Noreen E.; Yan, Norman D.; Walseng, Bjørn & Hessen, Dag Olav (2013). Differential short- and long-term effects of an invertebrate predator on zooplankton communities in invaded and native lakes. Diversity and Distributions: A journal of biological invasions and biodiversity.  ISSN 1366-9516.  19(4), s 396- 410 . doi: 10.1111/j.1472-4642.2012.00946.x Show summary

  Aim Forecasting the effects of invasive species remains difficult, because shortterm effects may be transitory and theories of long-term effects are poorly developed and rarely tested. Here, we compare zooplankton communities from freshwater lakes in Norway and Canada that differ in their duration of exposure to the invertebrate predator Bythotrephes longimanus, to aid in predicting its potential long-term impacts on Canadian zooplankton communities.

• Moe, Therese Fosholt; Brysting, Anne Krag; Andersen, Tom; Schneider, Susanne Claudia; Kaste, Øyvind & Hessen, Dag Olav (2013). Nuisance growth of Juncus bulbosus: the roles of genetics and environmental drivers tested in a large-scale survey. Freshwater Biology.  ISSN 0046-5070.  58(1), s 114- 127 . doi: 10.1111/fwb.12043
• Schneider, Susanne Claudia; Moe, Therese Fosholt; Hessen, Dag Olav & Kaste, Øyvind (2013). Juncus bulbosus nuisance growth in oligotrophic freshwater ecosystems: Different triggers for the same phenomenon in rivers and lakes?. Aquatic Botany.  ISSN 0304-3770.  104, s 15- 24 . doi: 10.1016/j.aquabot.2012.10.001

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• Hessen, Dag Olav (2017). The many lives of carbon. Reaktion Books.  ISBN 9781780238517.  272 s.
• Hessen, Dag Olav (2017). Vi. Samarbeid fra celle til samfunn. Cappelen Damm AS.  ISBN 978-82-02-52606-1.  262 s.
• Weslawski, Jan Marcin & Hessen, Dag Olav (2017). Size: Why are some animals small and other large?. Polish Institute of Oceanography.  ISBN 978-83-949491-0-5.  25 s.
• Hessen, Dag Olav (2016). Landskap i endring. Pax Forlag.  ISBN 978-82-530-3899-5.  159 s.
• Hessen, Dag Olav (2015). C. Karbon - en uautorisert biografi. Cappelen Damm AS.  ISBN 978-82-02-45867-6.  260 s.
• Hessen, Dag Olav (2015). Livet fra A til Å - en bok om deg. Cappelen Damm AS.  ISBN 978-82-02-47688-5.  91 s.
• Hessen, Dag Olav; Lie, Thore & Stenseth, Nils Christian (red.) (2015). Mendels arv - Genetikkens æra. Gyldendal Norsk Forlag A/S.  ISBN 978-82-05-45818-5.  440 s.
• Kleiven, Helga Flesche; Hessen, Dag Olav; Svensen, Henrik; Samset, Bjørn Hallvard; Østli, Kjetil & Kristiansen, Nina (2014). Isfritt. Spartacus.  ISBN 9788243008342.  160 s.
• Alfsen, Knut H.; Hessen, Dag Olav & Jansen, Eystein (2013). Klimaendringer i Norge. Universitetsforlaget.  ISBN 978-82-15-02158-4.  248 s.
• Alfsen, Knut H.; Hessen, Dag Olav & Jansen, Eystein (2013). Klimaendringer i Norge - forskernes forklaringer. Universitetsforlaget.  ISBN 9788215021584.  256 s.

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• Haugnes, Gunhild M.; Tallaksen, Lena M.; Vogt, Rolf David; Storelvmo, Trude; Hessen, Dag Olav; Stordal, Frode; Lefevre, Sjannie; Kääb, Andreas & Uggerud, Einar (2018, 27. august). Klimaforskerne tar temperaturen på tropesommeren. [Tidsskrift].  Titan.uio.no.
• Smedsrud, Morten Skipenes; Hessen, Dag Olav & Vogt, Rolf David (2018, 30. mai). Svekket livsgrunnlag for fossekall og røye. [Fagblad].  Apollon.
• Hessen, Dag Olav (2017). Impact of Noncoding DNA on Phenotype Evolution. Encyclopedia of Life Sciences.  ISSN 1476-9506. . doi: 10.1002/9780470015902.a0027507
• Jensen, Nina; Martinsen, Siri; Hessen, Dag Olav; Bøckman, Petter & Moen, Ole Martin (2017). Dyrene dør. Du lever som før?.
• Jensen, Thomas Correll; Walseng, Bjørn; Christoffersen, Kirsten Seestern; Novichkova, Anna; Chertoprud, Elena S.; Chertoprud, Mikhail V.; Makarova, O. L.; Dimante-Deimantovica, Inta; Sakharova, E. G.; Krylov, A. V.; Frisch, Dagmar & Hessen, Dag Olav (2017). The impact of geese on aquatic biodiversity in the high Arctic.
• Schultze, Sabrina; Poste, Amanda; Ruus, Anders; Hessen, Dag Olav; Andersen, Tom & Borgå, Katrine (2017). Do high levels of terrestrial DOM uptake lead to higher contaminant concentration and changes in energy allocation and growth? A study on three marine lower food web taxa.
• Wolf, Raoul; Andersen, Tom; Hessen, Dag Olav & Hylland, Ketil (2017). From genetic damage to population effects: How interactions of dissolved organic carbon and ultraviolet radiation affect Daphnia magna.
• Benestad, Esben Esther Pirell; Hessen, Dag Olav & Mühleisen, Wencke (2016). Til bunns i seksualiteten - en mailsamtale. Fanfare.  ISSN 1893-8698.  (7), s 14- 23
• Bernhoft, Aksel; Albihn, Ann; Hessen, Dag Olav; Holmboe-Ottesen, Gerd; Keilman, Nico; Børresen, Trond; Haug, Ruth; Nicolaysen, Anna Marie & Andersen, Regine (2016). Hvordan skal vi sikre et landbruk som kan fø oss i framtiden?. Show summary

  Menneskenes endring av naturen og jordas ressurser truer framtidens landbruk. Så hvordan skal den sårbare matproduksjonen best foregå på lang sikt når jordas befolkning øker?

• Eriksen, Thomas Hylland; Hessen, Dag Olav & Svensen, Henrik (2016). En røff guide til antropocen. Nytt Norsk Tidsskrift.  ISSN 0800-336X.  33(1-2), s 71- 83
• Grinde, Bjørn; Wilson, David Sloan; Lieberman, Jerry; Hessen, Dag Olav; Gule, Lars; Lieberman, Gin Kohl; Moene, Kalle; Gowdy, John & Krall, Lisi (2016). The Norway Project: A deep look at its lessons to help us to improve Our society. Full text in Research Archive.
• Hessen, Dag Olav (2016). Banch/Stim, I: Knut Stene-Johansen; Christian Refsum & Johan Henrik Schimanski (red.),  Å leve sammen. Roland Barthes, individet og fellesskapet.  Spartacus.  ISBN 978-82-304-01781.  Kapittel.
• Svensen, Henrik; Eriksen, Thomas Hylland & Hessen, Dag Olav (2016). Menneskeheten er inne i en ny geologisk epoke - antropocen. Aftenposten (morgenutg. : trykt utg.).  ISSN 0804-3116.
• Vogt, Rolf David; Gao, Pingchuan; Hessen, Dag Olav & Haaland, Ståle (2016). Effect of solar radiation on Dissolved Natural Organic Matter. Show summary

  Lakes and rivers are the main sources of drinking water in Nordic countries. For aesthetic and hygienic reasons high concentration levels of dissolved natural organic matter (DNOM) are not acceptable in drinking water. An increasing amount of DNOM in raw water sources for drinking water in Fennoscandia is thus raising our concerns. Moreover, the DNOM constitute an important transport mechanism for the flux of allochthonous nutrients to surface water. Once in the lake the DNOM photo-degrades due to adsorption of energy from sunlight. This causes its larger molecular weight (MW) compound to decompose into a variety of smaller organic photoproducts. Moreover, some of the DNOM is mineralized completely to inorganic compounds. Mineralization of DNOM causes a release of aluminum (Al) and iron (Fe) ions along with the release of orthophosphate (PO43-). The metal ions rapidly hydrolyze and form oxy-hydroxides which co-sorb phosphate and precipitate. Due to the removal of mineralized PO43- by subsequent precipitation with Fe- and Al-oxy hydroxides it is difficult to detect how much orthophosphate becomes mineralized by solar radiation. This is needed in order to assess the amount of this limiting nutrient becoming available for autotrophs. Thus the essence of this study is to test the option of using algae growth response as an indication of phosphorus release. Considerable research has been conducted comparing the changes in characteristics of the matrix that DNOM is in and structural characterization of DNOM, before and after solar exposure. A continuous increase in the relative contribution of lower to higher MW DNOM compounds along with a decrease in DOC concentration has been found with the extension of exposure time. This implies that the photochemical mineralization of DNOM by the photo-oxidation transforms the higher MW DNOM compounds into lower MW compounds, and that some of the DNOM is completely mineralized. This is further corroborated with fluorescence spectroscopy, indicating a decreased ratio of Humic to Fulvic acids in the DNOM as a response to sunlight exposure. This would imply that when sunlight is absorbed by DNOM, the average molecular weight is reduced. Results from assays showing increased algal growth imply that PO43- has been mineralized from DNOM due to photochemical reaction. On the other hand the growth response is not always significant. This may partly be due to concurrent heterotopic mineralization by bacteria.

• Edvardsen, Bente & Hessen, Dag Olav (2015). Genome size variation in microalgae”. Show summary

  Genome size among eukaryotic microalgae vary with a factor of more than 17 000. The rRNA gene copy number similarly vary more than 12 000 times. The lowest genome size and rRNA gene copy number has been found in picoplanktonic chlorophytes (Ostreococcus, 12 Mb) and ochrophytes (Nannochloropsis, 25 Mb) and the highest in large dinoflagellate cells (e.g. c. 450 Gb in Prorocentrum micans and 12000 rDNA copies in Akashiwo sanguinea). For taxa analysed so far, the genome size is correlated with cell size and carbon-content both between and within species. Cell size is also generally positively correlated with growth rate within a taxonomic group, and smaller genome size thus corresponds to higher growth rate. A great diversity of life cycles is found among microalgae including diploid (diatoms), haplo-diploid (haptophytes), or haploid (dinoflagellates, many chlorophytes). The nutrient-sparing hypothesis implies selection for small cells and genomes under nutrient limited conditions, and may explain why some groups have retained a haploid or a haplo-diploid life cycle. A biphasic life cycle may be favorable under variable environmental conditions through niche partitioning or provide escape from biotic pressures such as pathogens and grazers, but may get lost under stable conditions. Nutrient scarcity may however also promote smaller cells due to their larger surface : volume ratio. Here we have compiled published data on eukaryotic microalgal genome size, cell size and growth rate and added own data for haptophytes to compare patterns among taxonomic groups, reveal driving forces and relate this to life cycle strategies.

• Hessen, Dag Olav (2015). Evolusjon, naturvitenskap og mening : tilsvar å Geir Gellemos artikkel i forrige nummer. Kirke og kultur.  ISSN 0023-186X.  120(4), s 340- 341
• Wolf, Raoul; Andersen, Tom; Hessen, Dag Olav & Hylland, Ketil (2015). The influence of UVR and DOC on the genomic integrity of Daphnia magna.
• Wolf, Raoul; Varga, Lilia; Andersen, Tom; Hessen, Dag Olav & Hylland, Ketil (2015). Effects of Environmental Stress on the Genomic Integrity of Daphnia magna STRAUS, 1820.
• Bøckman, Petter; Hessen, Dag Olav & Sætre, Glenn-Peter (2014, 08. august). Homo futurus. [Tidsskrift].  Aftenposten Ammagasinet.
• Hessen, Dag Olav (2014). Albedo - og et grønnere Artktis, I: Henrik Svensen (red.),  Isfritt. Populærvitenskap som angår deg.  Spartacus.  ISBN 9788243008342.  Kapittel.  s 93 - 95
• Hessen, Dag Olav (2014). Den tause våren. Harvest : Mennesket & naturen.
• Hessen, Dag Olav (2014). En utrydningstruet art?. Klassekampen.  ISSN 0805-3839.
• Hessen, Dag Olav (2014). Fri vilje - biologisk umulig, men moralsk nødvendig?, I: Svein Harald Gullbekk (red.),  Ja, vi elsker frihet.  Dreyer Forlag A/S.  ISBN 978-82-8265-093-9.  Kapittel.  s 32 - 36
• Hessen, Dag Olav (2014). Høyere, tettere, gråere. Aftenposten (morgenutg. : trykt utg.).  ISSN 0804-3116.
• Hessen, Dag Olav (2014). Mer av alt. NRK - www.nrk.no.
• Hessen, Dag Olav (2014). Motorferdsel og demogratiske fikenblad. VG : Verdens gang.  ISSN 0805-5203.
• Hessen, Dag Olav (2014). Oljefondet som mulighet. Klassekampen.  ISSN 0805-3839.
• Hessen, Dag Olav (2014). Oljefondets etikk; både råd og forvaltning. Dagens næringsliv.  ISSN 0803-9372.
• Hessen, Dag Olav (2014). Oljefondets etiske mandat. Dagbladet.  ISSN 0805-3766.
• Hessen, Dag Olav (2014). Pose og sekk-nasjonen. Klassekampen.  ISSN 0805-3839.
• Hessen, Dag Olav (2014). På skattejakt i "søppel-DNA". Aftenposten (morgenutg. : trykt utg.).  ISSN 0804-3116.
• Hessen, Dag Olav (2014). Verdien av det ubetalelige, I: Henrik Svensen (red.),  Isfritt. Populærvitenskap som angår deg.  Spartacus.  ISBN 9788243008342.  Kapittel.  s 64 - 65
• Reusch, Marianne & Hessen, Dag Olav (2014). Kan forbud fremme frihet?. Dagbladet.  ISSN 0805-3766.
• Svensen, Henrik & Hessen, Dag Olav (2014). Eksperimentet, I: Henrik Svensen (red.),  Isfritt. Populærvitenskap som angår deg.  Spartacus.  ISBN 9788243008342.  Forord.  s 9 - 11
• Tønnessen, Morten; Tønnessen, Morten & Hessen, Dag Olav (2014, 12. november). – Et godt liv kan ikke realiseres i pelsdyrindustrien. [Fagblad].
• Aall, Carlo; Grønås, Sigbjørn; Hessen, Dag Olav; Hjertager, Audun; Hylland-Eriksen, Thomas; Innbjør, Linda; Jakobsen, Ove D; Kroglund, Andrew P.; Kvåle, Gunnar; Fossgard Sandøy, Ingvild; Svae, Per Hjalmar & Vetlesen, Arne Johan (2013). Opprop for De Grønne. Klassekampen.  ISSN 0805-3839.
• Hessen, Dag Olav (2013). Hva skal vi spise? : fortid som fasit : biologens kommentar. Tidsskrift for kulturforskning.  ISSN 1502-7473.  12(3-4), s 27- 29
• Lie, Thore & Hessen, Dag Olav (2013). Ut av Darwins skygge. Alfred Russel Wallace. Biolog.  ISSN 0801-0722.  4, s 10- 16
• Lier-Hansen, Stein; Vedeld, Pål; Armstong, Claire; Brekke, Kjell Arne; Clemetsen, Morten; Magnussen, Kristin; Hessen, Dag Olav; Nybø, Signe; Mäler, Karl-Göran; Aslaksen, Iulie; Schei, Peter Johan; Sørheim, Kristin; Bråten, Kristin Grønvik; Katerås, Finn & Sæther, Bent Arne (red.) (2013). Norges offentlige utredninger. Naturens goder - om verdier av økosystemtjenester. NOU - Norges offentlige utredninger. 2013-10.
• Frigstad, Helene; Andersen, T.; Hessen, Dag Olav; Jeansson, Åke Emil; Skogen, M.; Naustvoll, Lars Johan; Miles, Martin W.; Johannessen, Truls & Bellerby, Richard (2012). Long-term trends in carbon, nutrients and stoichiometry in Norwegian coastal waters: evidence of a regime shift.

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