Spatial distribution of transparent exopolymer particles in the Bransfield Strait, Antarctica

Abstract

Transparent exopolymer particles (TEP) are recognized to play an important role in the flux of exported carbon to the deep ocean. However, there is little information on how TEP standing stocks are affected by different hydrographic conditions and other relevant ecological factors in situ. This lack of knowledge is particularly serious for the Southern Ocean. During Austral summer 1999, the Strait of Bransfield presented high mesoscale variability. Two fronts were present, the Bransfield hydrographic front and a slope front along the South Shetland Islands and several mesoscale anticyclonic eddies and/or frontal meanders. The spatial distributions of biological properties were largely affected by this complex hydrography. Chlorophyll a (Chl a) (0.05–4.81 μg L−1), TEP (from undetectable to 346 μg GXeq L−1) and heterotrophic bacteria (HB) (1.7–9.4 × 105 cells mL−1) were positively correlated despite the wide hydrographic heterogeneity of the Bransfield Strait. Higher abundances of autotrophic biomass, and correspondly higher TEP and heterotrophic bacteria (HB), were found in the more stratified waters. TEP spatial distribution was mostly related to the abundance of autotrophic biomass although local high TEP concentrations were not matched by similarly high values of Chl a in some areas where diatoms were relatively abundant.