Abundance and distribution of transparent exopolymer particles in the estuarine turbidity maximum of Chesapeake Bay

Transparent exopolymer particle (TEP) concentrations were measured in the estuarine turbidity maximum (ETM) region of Chesapeake Bay during 8 research cruises over 2 yr. TEP concentrations ranged from 37 to 2820 mu g xanthan gum equivalent l(-1) and accounted for an estimated average (+/- SD) of 32 +/- 16% of particulate organic carbon (POC). Spatially averaged TEP and chlorophyll a (chl a) concentrations were positively correlated over the 2 yr period, although these parameters were rarely correlated on a sample-to-sample basis. Maximum TEP concentrations were often spatially separated from chl a maxima, suggesting that TEP in ETM regions is controlled by formation, concentration, and transport processes rather than proximity to precursor source material. Significant correlations between TEP and phaeophytin a, POC, dissolved organic carbon (DOC), total suspended solids, and degree of stratification were observed during some sampling periods. Settling tube experiments revealed a positive correlation between TEP concentration and the fraction of settling particulate matter, indicating either enhanced local aggregation and settling or transport and accumulation of aggregates formed elsewhere in the ETM region. These results indicate that TEP constitutes a very large fraction of POC in ETM regions, and suggest that TEP contributes to the formation and maintenance of ETM.