Seasonal dynamics of sea-ice protist and meiofauna in the northwestern Barents Sea

• Published in: Progress in oceanography 2023-11, Vol.218, p.103128, Article 103128
• Main Authors: Marquardt, Miriam, Goraguer, Lucie, Assmy, Philipp, Bluhm, Bodil A., Aaboe, Signe, Down, Emily, Patrohay, Evan, Edvardsen, Bente, Tatarek, Agnieszka, Smoła, Zofia, Wiktor, Jozef, Gradinger, Rolf
• Format: Article
• Language: English
• Subjects: Barents Sea; First-year ice; Foraminifers; Ice drift; Sea-ice biota; Seasonality; Sympagic
• ISSN: 0079-6611; 1873-4472; 1873-4472
• DOI: 10.1016/j.pocean.2023.103128

[Display omitted] •First seasonal study of sea-ice protist and meiofauna in the northwestern Barents Sea.•High December abundances strengthened notion of an active winter biota in the polar night.•Several findings suggesting sea ice as organic carbon reservoir beyond the productive season.•Ice meiofauna was dominated by pelagic taxa supporting the loss of older ice types favor pelagic-sympagic species. The rapid decline of Arctic sea ice makes understanding sympagic (ice-associated) biology a particularly urgent task. Here we studied the poorly known seasonality of sea-ice protist and meiofauna community composition, abundance and biomass in the bottom 30 cm of sea ice in relation to ice properties and ice drift trajectories in the northwestern Barents Sea. We expected low abundances during the polar night and highest values during spring prior to ice melt. Sea ice conditions and Chlorophyll a concentrations varied strongly seasonally, while particulate organic carbon concentrations were fairly stable throughout the seasons. In December to May we sampled growing first-year ice, while in July and August melting older sea ice dominated. Low sea-ice biota abundances in March could be related to the late onset of ice formation and short time period for ice algae and uni- and multicellular grazers to establish themselves. Pennate diatoms, such as Navicula spp. and Nitzschia spp., dominated the bottom ice algal communities and were present during all seasons. Except for May, ciliates, dinoflagellates, particularly of the order Gymnodiales, and small-sized flagellates were co-dominant. Ice meiofauna (here including large ciliates and foraminifers) was comprised mainly of harpacticoid copepods, copepod nauplii, rotifers, large ciliates and occasionally acoels and foraminifers, with dominance of omnivore species throughout the seasons. Large ciliates comprised the most abundant meiofauna taxon at all ice stations and seasons (50–90 %) but did not necessarily dominate the biomass. While ice melt might have released and reduced ice algal biomass in July, meiofauna abundance remained high, indicating different annual cycles of protist versus meiofauna taxa. In May highest Chlorophyll a concentrations (29.4 mg m−2) and protist biomass (107 mg C m−2) occurred, while highest meiofauna abundance was found in August (23.9 × 103 Ind. m−2) and biomass in December (0.6 mg C m−2). The abundant December ice biota community further strengthens the emerging notion of an active bi