IN-SITU TIME-SERIES MEASUREMENT OF INGESTION AND ABSORPTION RATES OF SUSPENSION-FEEDING BIVALVES - PLACOPECTEN-MAGELLANICUS

An adaptation of available methods is described for quantifying the ingestion and absorption rates of suspension-feeding bivalve molluscs exposed in situ to natural food sources and flow conditions. This new approach was used to follow the feeding response of the sea scallop Placopecten magellanicus (Gmelin) to short-term tidal cycle effects on current speed and seston quality in Lunenburg Bay, Nova Scotia. Unlike traditional methods, sampling is continuous and measurements of food uptake and utilization are averaged over selected time intervals (minutes to days). Scallop feeding activity varied markedly over a tidal cycle and periodic feeding activity accounted for a large proportion of food intake. Ingestion rates were not closely coupled with seston quantity, horizontal particle flux, or nutritional value as inferred from pigments, total organic and organic carbon and nitrogen content. The scallops did not alter absorption efficiency to adapt to short-term variations in diet quality.