AME 35:283-296 (2004)  -  doi:10.3354/ame035283

ABSTRACT: The abundance, size spectra and bacterial colonization of exopolymer particles were investigated in Antarctic sea ice and underlying water in the Bellingshausen Sea during April 2001. In addition to exopolymer particles (EP), different abiotic (temperature, salinity, ice texture, oxygen isotopic composition, inorganic nutrient concentrations) and biotic (particulate organic carbon/nitrogen, algal pigments, abundance and biomass of bacteria and diatoms) parameters were measured from the samples. The sea ice showed different communities occurring in physically distinct layers of the ice. Algal and bacterial biomass in the ice showed strong vertical gradients and ranged between 59.4 and 5140.4 μg C l^-1 and 8.8 and 119.4 μg C l^-1, respectively. EP concentrations in the sea ice were high, with EP abundance ranging between 10.2 and 260.1 × 10⁶ particles l^-1 and EP area between 3.4 and 92.1 cm² l^-1. Median EP concentrations in the ice exceeded under-ice values by 1 order of magnitude. Crude estimates of integrated sea ice EP carbon were equivalent to 14-32% of the integrated POC, and to 34-78% of the integrated diatom biomass. The estimated integrated EP carbon in sea ice exceeded the bacterial biomass by a factor of 10 to 20. The abundance of EP was inversely correlated with size of the particles. EP size spectra showed relatively flat slopes, indicating a relatively large contribution of larger particles. The bacterial colonization of individual EP in the ice and in the under-ice water was not significantly different. In contrast, due to the large difference of EP concentrations in the 2 habitats, the median proportion of attached bacteria was much higher in the ice (14.8% of the total bacterial number) than in the under-ice water (1.9% of the total bacterial number). The data suggest that EP are an integral component of Antarctic sea ice communities and that EP serve as important substrates for ice-associated bacteria. After the ice melts in spring, large amounts of EP are available to be released to the water, where they may significantly contribute to and alter the particle flux of the ice-covered Southern Ocean.

KEY WORDS: Sea ice · Antarctica · Exopolymer particles · Extracellular polymeric substances · Particle colonization · Bacteria · Diatoms