Potential nutritional contributions of bacterial exopolymer and suspended bacteria to the detritus feeding estuarine clam, Macoma balthica, were examined separately in laboratory 14C labelling experiments. Significant removal and assimilation of suspended bacteria by M. balthica was observed within two days, although the low clearance rates suggested planktonic bacteria may not be among its major food sources. Sediment-bound and dissolved bacterial exopolymer did not appear to be directly metabolized by M. balthica, as evidenced by the 1–2 week lag in 14C uptake into clam tissue.