Hydrobiologia 475/476: 505–511, 2002. E. Orive, M. Elliott & V.N. de Jonge (eds), Nutrients and Eutrophication in Estuaries and Coastal Waters. 505 © 2002 Kluwer Academic Publishers. Printed in the Netherlands. Physiological response of Spisula subtruncata (da Costa, 1778) to different seston quantity and quality Jose L. Rueda∗ & Aad C. Smaal Netherlands Institute for Fisheries Research (RIVO). P.O. Box 77, 4400 AB Yerseke, The Netherlands ∗Present address: Marine and Estuarine Ecology Unit, Department of Zoology and Entomology, University of Queensland, St. Lucia, Qld 4072, Australia E-mail:
[email protected] Key words: bivalve, feeding behaviour, filtration, ingestion, regulation Abstract Individuals of the bivalve Spisula subtruncata were fed a mixed diet comprising of sea water enriched with the diatom Phaeodactylum tricornutum and ashed silt within a range of concentrations, simulating natural conditions above pseudofaeces threshold. The designed ranges for total particulate matter were between 10 and 30 mg l−1and organic content of seston 15–40%. Filtration rate, rejection rate, ingestion rate and absorption rate were measured at those different conditions. Filtration rate and rejection rate were significantly correlated to total particulate matter and percentage of organic matter, with higher rates at higher values of total particulate matter and lower values of percentage organic matter. Ingestion rate was maintained at similar levels in all the treatments and organic enrichment of the ingested food occurred due to preingestive selection of the filtered material. A differential absorption rate occurred at different levels of organic matter in the diet with high rates at high values of the organic content of the diet.