Mortality and Physiological Responses with Regard to the Surf Clam, Mactra quadrangularis, Exposed to Chlorine

Carcinogenic disinfection by-products (DBPs) are formed as the result of the chlorination of power plant water cooling systems for biofouling purposes. Effects of cooling water chlorination are noteworthy topics of discussion as they greatly affect aquatic life and; thus, raise environmental concerns. This study aims to examine the chlorine effect on varying sizes of surf clams ( Mactra quadrangularis ) by evaluating the lethal response (time to 100% mortality) and sublethal physiological responses (filtration rate and oxygen consumption rate) in different chlorine concentrations. The present study will provide a proper guideline to determine chlorine injection concentration that serves as an antifouling compound. The maximum time to reach 100% mortality at the chlorine concentration of 0.5 mg L −1 in Group I (small) and II (large) was 568.0 ± 42.1 and 824.0 ± 25.0 h, respectively. Although the time to 100% mortality decreased sharply at 1.0 mg L −1 , no noticeable condition appeared above 1.0 mg L −1 . Physiological responses, such as filtration rate and oxygen consumption rate, at a sublethal concentration decreased significantly along with the residual chlorine concentrations. At below TRC 0.5 mg L −1 , M. quadrangularis showed weakened physiological responses, for instance declined feeding regimens, due to stress caused by chlorine. Longer exposure to chlorine at TRC lower than 0.5 mg L −1 can cause lack of growth, poor reproductive function, disease infection and even death in the M. quadrangularis population.