The microbiological contamination of an oyster growing area in Morocco: The Oualidia lagoon

Abstract

A 3-year bacteriological survey of an oyster growing area in Morocco, where the Japanese oyster (Crassostrea gigas) is grown showed that the contamination had a tendency to increase from winter to summer. The contamination of the lagoon was not continuous but intermittent. Animal manure and human recreational activities in the vicinity of oyster growing areas were important sources of pollution. Other sources of minor importance such as the installation of spats and traditional fishing activity contribute also to the contamination of the lagoon. The major source of pollution was from animal origin except during the summer when human contamination prevailed. Oysters harvested from this lagunar ecosystem contain fecal bacteria and may also contain bacterial pathogens. Thus, they may present a public health hazard and especially so in summer. It is hence advisable to rely oysters in clean waters or depurate them before marketing. Some control may also have to be placed on the use of the lagoon for human recreational activities to reduce the contamination during summer.