Estuaries Vol. 14, No. 2, p. 130-138 June 1991 The Influence of Mussel Beds on Nutrients in the Western Wadden Sea and Eastern Scheldt Estuaries RICHARD DAME Coastal Carolina College University of South Carolina Conway, South Carolina 29526 NORBERT DANKERS Research Institute for Nature Management P.O. Box 59 1790 Den Burg Texel The Netherlands THEO PRINS Delta Institute for Hydrobiological Research Vierstraat 28 4401 EA Yerseke The Netherlands HENK JONGSMA Research Institute for Nature Management P.O. Box 59 1790 Den Burg Texel The Netherlands AAD SMAAL Ministry of Transportation and Public Works Rijkswaterstaat Tidal Waters Division P.O. Box 8039 4330 EA Middelburg The Netherlands ABSTRACT: The uptake and release of materials by intertidal mussel beds were directly measured in two cultivated Dutch estuaries. Generally, chlorophyll a, seston, and particulate organic carbon were taken up, while ammonium, orthophosphate, and silicate were released. The observed rates were higher than values computed from organismic observations and similar to those observed for intertidal oyster reefs in South Carolina. Specific estuarine material turnover rates varied from I week to 38 weeks when calculated with mussel bed fluxes. The fastest turnover rates were for chlorophyll a and ammonium. These results support the idea that dense assemblages of bivalves are major components in the recycling of nutrients in estuaries. Introduction Mussel beds are dense heterotrophic communi- ties which are important economically and ecolog- ically to estuaries. These systems have high sec- 9 1991 Estuarine Research Federation 130 ondary production (Asmus 1987) and high energy flow (Kautsky and Evans 1987). They are capable of removing the phytoplankton population in the benthic boundary layer (Wildish and Kristmanson 0160-8347/91/020130-09501.50/0