Resuspension and growth ofOstrea edulis: A field experiment

Field experiments withOstrea edulis L. were conducted to examine the effects of resuspension on subtidal oyster growth in a small cove in malifax County, Nova Scotia. Removable racks with strips of fixed juvenile oysters were placed at 4 and 30 cm above a coarse sandy bottom (2 m depth). Summer growth was assessed weekly for 7 wk (July to August 1985) using silhouette images to follow individual change in shell area, a correlate of change in wet weight. Daily measurements of temperature, erosion/deposition (buried plate depth) and sediment chlorophyll suggested that sediment transport partially controlled the standing stock of benthic microalgae. Relative oyster growth per week was positively correlated with temperature. In addition, relative growth initially increased as the transport regime went from erosional to depositional (maximum growth near zero net transport) but growth rate declined with continued deposition. The relationship of oyster growth to gross changes in sediment chlorophyll showed a similar parabolic trend. The shape of these curves is similar to those obtained in published laboratory feeding experiments, which suggest beneficial effects of resuspension as a bivalve food supplement, but inhibition at higher levels due to decreased ingestion or dilution of food with inorganics. It is postulated that sand bottoms may provide more suitable resuspension environments than mud due to lower suspended loads over coarse sediments. Resuspension may be a valuable supplement to water column production as food for cultured bivalves, a factor of value in grow-out site selection.