Photosynthetically active radiation and microalgae and protist occurrence at ice stations of POLARSTERN cruise ARK-XIX/1

As compared to other seasons, species diversity of algae (total 40 taxa) was not low, but abundances (5,000-448,000 cells/l) were lower by one to two orders of magnitude.

Layers of high algal abundances were observed both at the bottom and in the ice interior. Inorganic nutrient concentrations (NO2, NO3, PO4, Si(OH)4) within the ice were mostly higher than during other seasons, and enriched compared to seawater by enrichment indices of 1.6-24.6 (corrected for losses through the desalination process). Thus, the survival of algae in Arctic pack ice was not limited by nutrients at the beginning of the productive season.