Lipids and diapause in Calanus spp. in a high-Arctic fjord: state-dependent strategies? Tracking lipids through the polar night

Abstract

Calanus copepods C. finmarchicus, C. glacialis and C. hyperboreus are keystone species in the Arctic marine ecosystem, constituting 70-90% of the zooplankton biomass. In high latitudes, the growing season is short and unpredictable, and the winter long and unproductive. These species have adapted flexible life histories, lipid accumulation, and a state of deep-water diapause to survive. Winter ecology is not well studied in the high-Arctic due to the difficulty of logistics. This study presents a high-resolution year-long time series of hydrological data, Calanus spp. stage composition, depth distribution and lipid content in a high-Arctic, seasonally ice covered fjord in Svalbard. The timing of descent to and ascent from diapause was of interest, specifically with regards to differences due to copepodite stage, prosome length, and lipid content. C. glacialis dominated the Calanus community and stages CIV and CV entered diapause. Females and males molted and ascended early 4 and 6 months before the spring phytoplankton bloom, respectively. Large, lipid-rich individuals molted and ascended first. Females reproduced in April, when there was nearly no food available, thus exhibiting capital breeding fueled by lipid stores. Descent to deep water began already in July, with the largest and most lipid rich individuals descending first.