Production of transparent exopolymer particles (TEP) by bivalves

In the marine environment, dissolved polysaccharide-rich organic matter coalesces to form transparent exopolymer particles (TEP). In turn, TEP has substantial impact on the flocculation of phytoplankton and other particles into aggregates (marine snow) which increase deposition of organic matter to the benthos. Previous studies have demonstrated that exudates and lysates from phytoplankton and bacteria contribute to the production of TEP. Little is known, however, about other sources of TEP precursors, especially in near-shore environments. The purpose of this study was to investigate production of TEP by several species of bivalves (Mytilus edulis, Argopecten irradians, Crassostrea virginica). In laboratory studies, several individuals of one bivalve species were isolated in static or recirculating seawater chambers and allowed to feed for up to 9 hr. In the field, groups of oysters were isolated in flow-through, benthic chambers and allowed to feed for 1 to 2 hr. Water samples were taken periodically and analyzed for TEP, dissolved organic carbon (DOC), and bacterial numbers. TEP concentration was determined using an Alcian Blue staining technique and quantified using a spectrophotometer. Results indicated that TEP concentration in chambers with actively feeding bivalves was significantly higher than in control chambers without bivalves. No significant differences in bacterial numbers were found between control and experimental chambers suggesting that the effects of bacteria were similar in all treatments. Mixed results were obtained for DOC concentration. Our results indicate that bivalves do produce TEP, probably during feeding when large volumes of water pass over mucus-coated feeding structures. We suggest that bivalves may be an important source of TEP in near-shore waters.