| Abstract: | During two consecutive cruises to the Eastern Central Arctic in late summer 2012,we observed floating algal aggregates in the melt-water layer below and betweenmelting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter)aggregates had a mucous consistency and were dominated by typical ice-associatedpennate diatoms embedded within the mucous matrix. Aggregates maintainedbuoyancy and accumulated just above a strong pycnocline that separated meltwaterand seawater layers. We were able, for the first time, to obtain quantitativeabundance and biomass estimates of these aggregates. Although their biomass andproduction on a square metre basis was small compared to ice-algal blooms, thefloating ice-algal aggregates supported high levels of biological activity onthe scale of the individual aggregate. In addition they constituted a foodsource for the ice-associated fauna as revealed by pigments indicative ofzooplankton grazing, high abundance of naked ciliates, and ice amphipodsassociated with them. During the Arctic melt season, these floating aggregateslikely play an important ecological role in an otherwise impoverishednear-surface sea ice environment. Our findings provide important observationsand measurements of a unique aggregate-based habitat during the 2012 record seaice minimum year. |
