Research Product

A fully enclosed test system was developed both to assess potential adverse effects of microbial pest control agents on nontarget aquatic invertebrates and to monitor their fate and survival. Eastern oysters Crassotrea virginica were exposed to various microbial pest control agents including the vegetative bacterium Pseudomonas fluorescens, bacterial spores of Bacillus sphaericus, and fungal spores of Colletotrichum gloeosporioides f. sp. aeschynomene. After an exposure of 3 d for the fungus, 14 d for the bacterial spores, and 7 d for the vegetative bacterial cells, half the oysters were placed into a fully enclosed 60 l aquarium equipped with a recirculating water system which passed water through an ultraviolet-irradiation sterilizer at a rate of 1 l min-1. The remaining oysters were placed into wire cages maintained in Santa Rosa Sound, Pensacola, Florida, USA. Plate counts, performed on homogenized oyster tissues, revealed that all of the microbial pest control agents were found in oysters after exposure. Oysters depurated each microorganism at a different rate. None of the agents colonized the oysters. For all microbes tested, rates of clearance from the oysters in the enclosed UV light depuration system were similar to rates of clearance from the oysters in Santa Rosa Sound. Histological examination of oyster tissues detected P. fluorescens and B. sphaericus in the gut and C. gloeosporioides in the gill. Spore germination was not observed and no apparent signs of infectivity or pathogenicity were detected.