Pivotal role of sea ice sediments in the seasonal development of near-shore Arctic fast ice biota

Abstract

The impact of sea ice sediments on the seasonal development of sea ice biota was assessed in Alaskan nearshore fast ice. Ice, water, and seafloor sediment were sampled in spring 2002 and 2003 at 2 locations. Light in the sediment-loaded sea ice location (total particle load = 106 g dry mass, DM, m-2) was reduced by more than 99% compared to the clean ice location (total particle load = 6 g DM m-2). Strong bottom ice algal blooms developed in sediment-free fast ice, reaching their maximum of 330 ug chl a l-2 (36 mg chl a m-2) in late May. Pigment levels in sediment-laden ice never exceeded 9 μg chl a l-1 (1 mg chl a m-2). In the water column, pigment levels remained below 1 μg chl a l-1 (<5 mg chl a m-2) under both clean and sediment-laden ice. With increasing ice algal biomass, the δ13C ratio of sea ice particulate organic matter (POM) in clean ice increased from -25% in February to -16%o in May, while no and little enrichment was observed in sediment-laden ice and pelagic POM, respectively. The abundance of ice metazoans in clean ice increased with progressing season from 17 700 (Feb) to 276 200 ind. m-2 (May), dominated by nematodes and ice-associated polychaete juveniles. In sediment-laden ice, maximum abundance was 16 600 ind. m-2 (May). Abundances of meroplanktic polychaete juveniles were at least one order of magnitude below abundances in the ice, suggesting sea ice is an important feeding habitat for these young life stages. Sediment within the ice had a profound impact on sea ice biota, and delayed or inhibited the spring bloom development. ©nter-Research 2009.