Negative effects of sediment deposition on grazing activity and survival of the limpet Patella vulgata

Sediments are likely to influence the distribution of limpets and dominant sessile species on intertidal rocky shores by smothering and interfering with feeding activity. This hypothesis was tested by field observations and laboratory experiments in which the effects of different amounts and grain sizes of sediments on the grazing and survival of the limpet Patella vulgata L. were measured. On rocky shores close to Plymouth (south-west UK), natural patchiness of sediment deposits was related to the distribution of P. vulgata and macroalgae. Sediments severely impaired P. vulgata. Even a similar to 1 mm thick layer of sediment (equivalent to 50 mg cm(-2)) decreased grazing activity by 35 %, with total inhibition and mortality at loads of 200 mg cm(-2) of fine sediments. Coarse sediments had less severe effects than fine sediments.