Abstract
Juvenile oysters, Crassostrea virginica (Gmelin), were fed on an artificial diet consisting of microgel particles, microcapsules, kaolin, and dissolved trace metals. The effects of both the type of agitation and the addition of dispersants and antibiotics on the stability of food-particle suspensions and oyster growth were determined. Agitation of cultures with a magnetic stirrer bar, instead of agitation with bubbled air, reduced losses of small (2.1–4.5 μm) food particles from suspension and improved oyster growth. The addition of 10 mg· 1 −1 of the lignosulphonate dispersant Reax 100 M together with 5 mg· 1 −1 each of the antibiotics rifampicin and chloramphenicol significantly reduced bacterial concentrations associated with the artificial diet and reduced the clumping and loss of food particles from suspension. The addition of the dispersant/antibiotic mixture reduced variation among experiments in the growth of oysters fed on the artificial diets, to between 41 and 64% of the growth of algal-fed oysters. Experimental evidence suggested that reduced variation in oyster growth was due to an indirect effect of the antibiotics on the qualitative composition of bacterial populations present in the oyster cultures.
Published Version
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