Biomass and production of zoobenthos in the Grevelingen estuary, the Netherlands☆

Abstract The Grevelingen estuary has an area of 140 km 2 with 4 km 2 of salt marshes and 55 km 2 of tidal flats. The tidal range is 259 cm, salinity about 15·0‰Cl − . Biomass and annual production of the five quantitatively most important benthic animals, viz. Littorina littorea, Hydrobia ulvae, Cardium edule, Macoma balthica and Arenicola marina were determined at six stations. Combined with an assessment of the benthic biomass in the whole estuary, this enabled us to make an estimate of the total production of these species. Data on the production of Mytilus edulis were derived from fisheries statistics. The total benthic secondary production for the whole estuary is estimated at 50·3 – 57·4 g ash-free dry weight m −2 year −1 , expressed as somatic growth. The place of the zoobenthos in the estuarine foodweb is discussed.