Compiled data overwintering Multical 2023

AbstractWinter ocean warming (OW), driven by the influx of warm Atlantic water masses, and acidification (OA) are threatening Arctic marine ecosystems. However, their potential synergistic effects are poorly understood, especially during the Polar Night when marine species are particularly vulnerable to stressors. In this study, we tested our novel Stressed Overwintering Bottleneck Hypothesis (SOBH), that warming will disrupt Calanus glacialis overwintering by impairing fitness-related traits linked to survival and reproduction. We exposed C. glacialis, a pivotal Arctic secondary producer, to current and projected future OW levels (0 °C and 4 °C) and OA levels (pH 8.0 and 7.4-7.3) for 53 days during the middle of the Arctic Polar Night. We evaluated survival, development, and physiological mechanisms such as oxygen consumption, lipid depletion, DNA damage, and the expression of nine targeted genes related to oxidative stress responses and damage repair. OW alone did not significantly affect C. glacialis mortality; however, OA increased copepod survival at 0 °C. Notably, their combined effects (OWA) synergistically doubled mortality, as predicted by SOBH. Warming also accelerated moulting from copepodite stage V to adulthood as early as December, and increased respiration rates could deplete lipids entirely by early March, approximately 1 to 4 months before the spring algal bloom, further supporting SOBH. DNA damage and gene expression patterns indicated low investment in maintenance and damage repair. Collectively, these findings reveal new mechanisms by which OW and OA synergistically threaten overwintering Calanus copepods: by drastically increasing mortality, accelerating moulting, raising metabolic rates, and causing early lipid depletion. These effects create month-long phenological mismatches among overwintering survival, energy reserves, reproduction, and primary production. Such Polar Night bottlenecks in foundational secondary producers like Calanus copepods threaten to constrict fragile Arctic marine food webs amid increasing OW and OA threats. DATA: <br>Compiled data sheet of the long-term multistressor C. glacialis experiment conducted as part of the research project: MULTICAL of Jildou Dijkstra at the University Cente in Svalbard between Oktober 2022 and June 2023. To study the effects of ocean warming and acidification on overwintering C. glacialis individuals were kept at different pH (7.5 and 8) and temperature (0 and 4 °C) combinations for a period of 53 days during which oxygen consumption, mortality, body size, lipid volume, and molting were documented. All data is recorded by Nele thomsen, Luise Schott, and Jildou Dijkstra.