Annual patterns in algal pigment distribution in Arctic first year ice during the MOSAiC expedition 2019/2020

Algal pigment concentrations were retrieved from samples from first-year (FYI) ice, during the whole MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) in 2019 to 2020. During MOSAiC, RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. Sea ice data were collected starting with the onset of the study, at 85 degrees north and 137 degrees east, following the drift towards the Fram Strait, and returning to the North Pole in the last leg of the expedition. Ice cores were collected at the various coring sites together with teams ICE and BGC (Nicolaus et al. 2022), to study the development of pigment patterns over time, on 3 specific ice-locations. Altogether, 292 samples have been collected and analysed. Ice cores were sliced in sections of 5-10 cm before analyses. Each of the sections was melted at room temperature after additions of filtered ambient seawater, under dark conditions. After extraction in 90 % acetone, samples were analysed using high-performance liquid chromatography (HPLC) on a Waters system (AWI). Algal pigments contain a multiple set of information. Firstly, pigment concentrations can show the presence of algal biomass in the various domains sampled. Secondly, marker pigments can reveal seasonal and temporal dynamics in algal community structure, by discerning specific algal classes like diatoms, cryptophytes, haptophytes and chlorophytes that have specific roles in biogeochemical cycles. Thirdly, certain pigments are indicative of the (photo)-physiological state of micro-algae and fourth, degradation products of the main chlorophyll a pigment further give an indication about senescence and grazing in the various habitats.