Effects of pH on filtration of freshwater pearl mussel Lamellidens marginalis, Lamarck (Bivalvia: Unionidae) under laboratory conditions

The study was conducted to evaluate the effects of pH on the filtration rate of freshwater pearlmussel Lamellidens marginalis under laboratory conditions. Three treatments were used in triplicate;treatment 1 (T1) at pH 7.5, treatment 2 (T2) at pH 8.0 and treatment 3 (T3) at pH 8.5. Ten mussels werestocked in each aquarium with continuous aeration. After 48 hours, 40 ml eutrophicated water having 34.75 x105 to 36.0 x 105 cells/ml of phytoplankton were provided in each aquarium. Initial concentration ofphytoplankton was 14400±360.55, 13900±360.55 and 14133± 404.14 cells/ml, whereas the finalconcentrations were 10300±100.00, 8300±200.00 and 10333±57.73 cells/ml in T1, T2 and T3, respectively.The reduction rate was consistently lower in T2 when compared to other treatments. Mussels of T2 (pH 8.0)exhibited significantly higher filtration rate (p<0.05) over T1 (pH 7.5) and T3 (pH 8.5) at all sampling times.The minimum filtration rate 58.03±32.79 ml/mussel/h was found in T3 after 1 h exposure, whereas thehighest filtration rate 110.94 ± 21.68 ml/mussel/h was obtained in T2 after 2 h exposure. The resultsconcluded that the pH has a clear effect on feeding habit of freshwater pearl mussel and pH 8 providesenvironment friendly to maximize the filtration of L. marginalis.