Under ice plankton and lipid dynamics in a subarctic lake

• Published in: Journal of Plankton Research
• Main Authors: Kers, Erwin Laurens, Leu, Eva, Amundsen, Per-Arne, Primicerio, Raul, Kainz, Martin, Poste, Amanda Elizabeth
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2024
• Subjects: Subarctic; Copepods
• Online Access: https://hdl.handle.net/10037/34472; https://doi.org/10.1093/plankt/fbae018

Climate warming causes shorter winters and changes in ice and snow cover in subarctic lakes, highlighting the need to better understand under-ice ecosystem functioning. The plankton community in a subarctic, oligotrophic lake was studied throughout the ice-covered season, focusing on lipid dynamics and life history traits in two actively overwintering copepods, Cyclops scutifer and Eudiaptomus graciloides. Whereas C. scutifer was overwintering in C-IV to C-V stage, E. graciloides reproduced under ice cover. Both species had accumulated lipids prior to ice-on and showed a substantial decrease in total lipid content throughout the ice-covered period: E. graciloides (60%–38% dw) and C. scutifer (73%–33% dw). Polyunsaturated fatty acids of algal origin were highest in E. graciloides and declined strongly in both species. Stearidonic acid (18:4n-3) content in E. graciloides was particularly high and decreased rapidly during the study period by 50%, probably due to reproduction. The copepods differed in feeding behavior, with the omnivore C. scutifer continuing to accumulate lipids until January, whereas the herbivorous E. graciloides accumulated lipids from under-ice primary production during the last months of ice-cover. Our findings emphasize the importance of lipid accumulation and utilization for actively overwintering copepods irrespective of the timing of their reproduction.