Abstract
Oysters in suspended aquaculture filter out particulates from the water column and release pseudofeces and feces (collectively called biodeposits) back to the water column. These biodeposits consist of dense assemblages of labile organic matter that quickly settle to the sediment surface. To properly quantify the environmental effects of biodeposition from suspended aquaculture, it is necessary to determine where the biodeposits settle. An analytical/numerical model was developed for suspended aquaculture systems to predict the spatial distribution of biodeposits; input parameters include water depth, tidal elevation, biodeposit settling rate, and wind and tidally driven current velocity. The biodeposit model was validated in three shallow Cape Cod, Massachusetts, estuaries characterized by low-energy hydrodynamics. For each site, model-predicted carbon deposition was regressed against measured carbon remineralization (determined from sediment oxygen uptake) obtained from intact sediment cores collected along a gradient of predicted carbon deposition. Results showed that in summer, nearly all carbon deposited was remineralized but that the fraction of deposited carbon that is remineralized decreases considerably with declining temperatures in the fall. The simple analytical/numerical model developed and validated in this study provides a tool for commercial oyster growers and environmental managers to assess the effect of organic matter deposition by suspended oyster aquaculture over the growing season. This approach can be applied in shallow depositional coastal systems.