Acute Toxicity of Ammonia and Nitrite to Sea Bream, Sparus aurata (Linnaeus, 1758), in Relation to Salinity

Abstract

Sea bream, Sparus aurata, is one of the most important fish species that is commonly cultured in the Mediterranean and the eastern coasts of the Atlantic Ocean. The life cycle of sea bream in its natural habitat passes through hyposaline and hypersaline lagoons. It is important to determine the tolerance of the fish to nitrogenous compounds for aquaculture at maximum stocking densities. In the present study, a series of acute experiments were performed to evaluate the effect of salinity on ammonia and nitrite toxicity to sea bream. The fish were exposed to different ammonia and nitrite concentrations according to the static renewal methodology at three different salinities (10, 20, and 30ppt) and at a temperature of 20C and a pH of 8.2. The toxic effect of total ammonia nitrogen (TAN) and nitrite nitrogen (NO2-N) decreased with increasing salinity levels (P<0.001). Acute toxicity (96-h lethal concentration 50 [LC50]) values of TAN were determined to be 5.93, 11.72, and 19.38mg/L at 10, 20, and 30ppt salinity, respectively. The 96-h LC50 values of NO2-N were determined to be 370.80, 619.47, and 806.33mg/L at 10, 20, and 30ppt salinity, respectively. Results indicate that sea bream is less tolerant to ammonia but more tolerant to nitrite compared with some other fish species.