Production of transparent exopolymer particles (TEP) by the eastern oyster Crassostrea virginica

Transparent exopolymer particles (TEP) play an important role in aggregation, phytoplankton bloom dynamics and the fate of organic carbon. Various types of plankton are known to release exopolymers that contribute to the TEP pool. Little is known, however, about other potential sources of TEP and TEP precursors in the oceans, especially in nearshore waters. Suspension-feeding bivalves can form dense assemblages in coastal waters and can process large volumes of water during feeding activities (e.g. 5 1 h(-1) g(-1) dry wt). They secrete mucus to maintain clean body surfaces and to aid in capturing and transporting food material. We hypothesized that mucopolysaccharides, which are released from bivalves in dissolved or particulate form, contribute to the TEP pool. To test this hypothesis, laboratory experiments were carried out to measure the concentration of TEP and DOC in chambers with actively feeding oysters Crassostrea virginica over a 9 h period. Field experiments were conducted to measure TEP and DOC production by oysters in situ, using clear Plexiglas chambers on an intertidal sand-flat in New Brunswick, Canada. TEP concentrations were determined with an Alcian blue staining technique and spectrophotometric detection. DOC concentrations were determined using high-temperature catalytic oxidation (HTCO) with a platinum catalyst. Laboratory results indicated that oysters significantly enhanced TEP and DOC concentrations compared to control levels over 9 h. Likewise, field experiments demonstrated elevated TEP concentrations in experimental chambers compared to control treatments. Our results support the hypothesis that oysters contribute to the production of TEP in coastal marine ecosystems.