Effects of suspended solids associated with dredging operations on estuarine organisms

During dredging and disposal operations, there is an increase in the suspended solids in the area of activity. These resuspended sediments can adverse impact biota. The suspended solids concentrations during various dredging and disposal operations in San Francisco Bay were monitored. The results of this monitoring were integrated with the results of a suspended solids test performed at the Bodega Marine Laboratory to develop a matrix of potential adverse effects on indigenous organisms under various suspended solids loadings. The matrix indicates that under winter condition of low temperature and high dissolved oxygen adults of most species should not be adversely influenced during periods of either dredging or disposal. However, during summer months, if temperature increases to above18\degC and dissolved oxygen drops below two parts per million mortality of sensitive species in the lower water column may result during disposal operations. The field investigations indicated that dredging could create a fluff zone at the sediment-water interface which because of its persistence might have adverse influence on benthic organisms.