Physiological and sanitary condition of the white clam Dosinia ponderosa collected from a coastal area impacted by shrimp farm effluent

Abstract

White clams (Dosinia ponderosa) were collected near an effluent outlet of shrimp farms to measure the impact of the discharge. Clams were collected at 50, 150, and 300 m from the discharge area. Environmental parameters at each sampling site were determined and the physiological, stress, and health conditions of the clams were recorded. Water and sediment qualities were negatively affected by effluent discharge at 50 and 150 m. Similarly, physiological and stress conditions of clams from the impacted areas were impaired at 50 and 150 m from the discharge zone. Glucose, lactate, cholesterol, and alanine aminotransferase levels were altered and transcription of heat shock proteins 70 and 90 were over-expressed in these clams. The health condition of clams was not affected: bacterial loads of aerobic mesophiles, fecal coliforms, Staphylococcus aureus, Salmonella sp., and Vibrio cholerae remained below international safety levels. No effects of effluents were detected on most of the parameters at 300 m. In summary, discharge of effluents by shrimp farms had a negative impact on environmental quality and on physiological conditions of white clams within a radius of at least 150 m from the outlet.