AE was determined by the pulse-chase radiolabeled feeding technique (Wang and Fisher, 1999). There were five replicate individuals for each bivalve in each treatment. An individual bivalve was placed in a polypropylene beaker containing 1 l of filtered seawater. Radiolabeled sediment was added at a density of 1.5 mg (dry weight) l21 to avoid pseudofeces production by the bivalves.