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Temporal and spatial variations in the composition of seston available to the suspension feeder Crassostrea virginica

1986; Elsevier BV; Volume: 23; Issue: 3 Linguagem: Inglês

10.1016/0272-7714(86)90034-x

1096-0015

Joseph A. Berg, Roger I. E. Newell,

Wastewater Treatment and Nitrogen Removal

Seston, the food resource of suspension feeders such as the oyster Crassostrea virginica, was monitored monthly over a period of 18 months in adjacent subestuaries of the Choptank River, Maryland. Measurements of seston concentration (mg l−1), as well as estimates of seston food quantity and quality were made at hourly intervals over a 10 hour period in water collected from 25 cm above the sediment surface. Estimates of seston food ‘quantity’ were based on the amounts of particulate organic material (POM), particulate inorganic material (PIM), particulate organic carbon (POC), particulate organic nitrogen (PON), chlorophyll a and energy content per unit volume of water. Estimates of food ‘quality’ were based on the amounts of POC, PON and energy content per unit dry weight of seston. Estimates of seston food quality, while variable from month to month, were similar in the two systems while seston concentration and estimates of seston food quantity were much greater in the Tread Avon River. We propose that higher concentrations of food in the seston enable oysters in the Tred Avon to attain the larger adult size observed. Seston concentration and estimates of seston food quantity were lowest during the winter and greatest during the summer. Estimates of seston food quality were similar over the seasonal cycle with a slight decrease during the summer. This decrease is attributed to the disproportionate increase of PIM relative to POM with increasing seston concentration. There was a marked difference in seston concentration and estimates of seston food quantity in the Tred Avon, but not in Broad Creek, between the spring of 1982 and the same period in 1983. We suggest that this is due to the greater precipitation during the spring of 1983. Since the Tred Avon drains a greater watershed than Broad Creek, the observed precipitation had a greater impact on the seston in the Tred Avon system than to Broad Creek.