Effect of food and light on the development of the Arctic copepod Calanus glacialis during the winter-spring transition

We investigated potential impacts of earlier sea ice retreat and timing of the spring bloom on overwintering copepodites (CIV) of Calanus glacialis, the main primary consumer in Arctic shelf seas. By field studies and laboratory experiments, we following the feeding and growth of C. glacialis under different light (dark/light) and food (starved/fed) conditions, spring 2013, in high-Arctic Svalbard. We carefully monitored the molting rate, lipid content and fatty acid composition in field and laboratory specimens, simultaneously, over a 2 months period. Field results indicated that CIV were in dormancy (diapause) until the light returned. Both light and food appeared to be important “wake-up” triggers from diapause. Growth and development, however, were strongly regulated by food. In field, the main molting from CIV to CV occurred 2-3 weeks after the onset of the spring bloom (June) which corresponded well with the experimental results where the fed ones molted end of April after 3 weeks of intensive feeding, while the starved ones not. Our results suggest that C. glacialis quickly respond to external cues, being able to adapt to a changing Arctic.