Response of mussel Brachidontes striatulus to chlorination: an experimental study

Though the brackish-water mussel, Brachidontes striatulus (Hanley) (syn. Modiolus str iatulzrs) is an important fouling animal in power station cooling circuits, there are no published studies on the tolerance of this species to chlorination. Mortality pattern as well as physiological behaviour (byssus thread production, foot activity index and filtration rate) of three different size groups (7, 18 and 25 mm shell length) of B. striatulus, were studied at different chlorine concentrations (0-5 mg l(-1)). At 1 mg l(-1) chlorine residual, 7 mm size group mussels showed 100% mortality in 468 h (20 days) and 25 mm size group mussels in 570 h (24 days). At relatively high levels of chlorine residuals (5 mg l(-1)), 100% mortality in 7 and 25 mm size groups took 102 and 156 h, respectively. The exposure time to chlorine required for 100% mortality of B. striatulus is much lower than that reported for some other common fouling mussels. Chlorine concentration significantly affected the mean time of death for all size groups of mussels. All size groups showed progressive reduction in physiological activities such as filtration rate, foot activity index and byssus thread production when chlorine residuals were increased from 0 to 1.5 mg l(-1). Reduction in physiological activities of mussels was strongly correlated with the concentration of chlorine. (C) 1997 Elsevier Science B.V.