Vertical distribution of exopolymer particles in sea ice of the Fram Strait (Arctic) during autumn

Abstract

The concentration and size distribution of exopolymer particles were measured in and below pack ice in the Fram Strait area during autumn 1999. Vertical profiles of exopolymer particles were determined in young, first-year and multi-year sea ice. In addition, a variety of abiotic parameters (temperature, salinity, NO 2 , PO 4 , NO 3 , SiO 2 ) and biotic parameters (particulate organic carbon [POC] and nitrogen [PON], chlorophyll a [chl a], abundances of diatoms and bacteria) were measured. Median abundances and areas of exopolymer particles in the different ice types (3.17 x 10 6 to 4.90 x 10 6 particles 1 -1 and 4.6-6.9 cm 2 1 -1 , respectively) exceeded median concentrations in the under-ice water (0.56 x 10 6 particles 1 -1 ; 0.6 cm 2 1 -1 ) by 1 order of magnitude. Exopolymer particle concentrations in sea ice were highest in the interior of the sea ice and were significantly correlated with chl a as well as with the abundances of pennate diatoms, centric diatoms and bacteria. Our data indicate that pennate diatoms are the main producers of exopolymer particles in sea ice. The observed exopolymer particle-size spectra in both sea ice and under-ice water differed from those commonly reported for exopolymer particles in pelagic environments by a relatively large fraction of large particles. Crude estimates of integrated exopolymer particle carbon indicate that these particles can be important components in the context of food-web structure and organic carbon dynamics in the sea ice habitat. The high concentrations of exopolymer particles in the sea ice will also impact the fate of other particles during ice melt.