Transparent exopolymer particles (TEP) from suspension feeders andtheir effects on particle aggregation

摘要

Transparent exopolymer particles (TEP) can form from dissolved precursors released by phytoplankton. Recent studies have also demonstrated that benthic suspension feeders, such as bivalves, can contribute significantly to the TEP pool in coastal waters. Whereas TEP from phytoplankton is important for the aggregation of suspended material, the role of TEP from suspension feeders on aggregate formation is unknown. The purpose of this study was to test the hypothesis that organic compounds, including TEP, released from suspension feeders enhance the formation of particle aggregates in coastal waters. In laboratory experiments, TEP was collected from blue mussels (Mytilus edulis) and sea vases (Ciona intestinalis) using previously established methods. One of two particle types, silica-amino beads or diato-maceous earth (ca. 10 mu m), were then added to seawater with and without TEP produced by the animals. Bottles (250 ml) containing suspended particles were placed on a roller table and rolled for 48 hours. Changes in the size distribution of particles in each jar were followed over time by means of an electronic particle counter, and aggregates larger than 100 mu m were counted using a rafter cell and microscope. Dissolved and total organic carbon and bacterial concentrations were determined before and after the rolling period. Results indicate that significantly more particle aggregates are produced in seawater containing TEP from suspension-feeding animals than in control water. Aggregation of both particles types was similarly enhanced. Our results suggest that organic material released by suspension-feeders can enhance aggregate formation and hence the deposition of material to the benthos.