A crude awakening: effects of crude oil on lipid metabolism in calanoid copepods terminating diapause

Author Posting. © University of Chicago, 2019. This article is posted here by permission of University of Chicago for personal use, not for redistribution. The definitive version was published in Biological Bulletin 237(2), (2019): 90-110, doi: 10.1086/705234.Calanus finmarchicus and Calanus glacialis are keystone zooplankton species in North Atlantic and Arctic marine ecosystems because they form a link in the trophic transfer of nutritious lipids from phytoplankton to predators on higher trophic levels. These calanoid copepods spend several months of the year in deep waters in a dormant state called diapause, after which they emerge in surface waters to feed and reproduce during the spring phytoplankton bloom. Disruption of diapause timing could have dramatic consequences for marine ecosystems. In the present study, Calanus C5 copepodites were collected in a Norwegian fjord during diapause and were subsequently experimentally exposed to the water-soluble fraction of a naphthenic North Sea crude oil during diapause termination. The copepods were sampled repeatedly while progressing toward adulthood and were analyzed for utilization of lipid stores and for differential expression of genes involved in lipid metabolism. Our results indicate that water-soluble fraction exposure led to a temporary pause in lipid catabolism, suggested by (i) slower utilization of lipid stores in water-soluble fraction-exposed C5 copepodites and (ii) more genes in the β-oxidation pathway being downregulated in water-soluble fraction-exposed C5 copepodites than in the control C5 copepodites. Because lipid content and/or composition may be an important trigger for termination of diapause, our results imply that the timing of diapause termination and subsequent migration to the surface may be delayed if copepods are exposed to oil pollution during diapause or diapause termination. This delay could have detrimental effects on ecosystem dynamics.We thank the Department of Biology at the Norwegian University of Science and Technology (NTNU) for additional funding for ES’s stay at Woods Hole Oceanographic Institution (WHOI); Christoffer H. Hilde for help in the field and in the lab; Siv Anina Etter, Øystein Leiknes, Sofia Soloperto, and Clara P. Igisch for help with the fieldwork; Justyna Świeżak, Mari-Ann Østensen, and Signe D. Løvmo for experimental assistance; and Hanny Rivera for help with bioinformatic analyses at WHOI. The RNA-sequencing work was provided by the Genomics Core Facility (GCF). The GCF is funded by the Faculty of Medicine and Health Sciences at NTNU and the Central Norway Regional Health Authority. AMT was funded by the National Science Foundation (award no. OPP-1746087).2020-10-0