RESPIRATORY ADJUSTMENT OF DREISSENID MUSSELS (DREISSENA-POLYMORPHA AND DREISSENA-BUGENSIS) IN RESPONSE TO CHRONIC TURBIDITY

A laboratory study was conducted to determine the effect of chronic tu rbidity (using bentonite clay) at medium and high temperatures on resp iration of two exotic mussel species, Dreissena polymorpha and Dreisse na bugensis. Populations of D. polymorpha from Lake Erie and the Ohio River and D. bugensis from Lake Erie were acclimated for 4 weeks to on e of four temperature-turbidity combinations: 25 degrees C - 0 nephelo metric turbidity units (NTU), 25 degrees C - 80 NTU, 15 degrees C - 0 NTU, and 15 degrees C - 80 NTU. At the end of the acclimation period, respiration was measured at both 0 and 80 NTU using a closed, flow-thr ough system with a Clark-type polarographic microelectrode. Mass-speci fic respiration rates were computed as Vo(2) (= mu L O-2 onsumed-mg sh ell-free dry mass(-1). h(-1)). Results showed that size, temperature, acclimation turbidity, and measurement turbidity significantly affecte d VO2 rates. An interaction between acclimation turbidity and measurem ent turbidity suggests that dreissenid mussels adjusted their metaboli c rate in response to chronic exposure to turbidity. Mussels acclimate d to higher levels (80 NTU) of turbidity did not experience as large a percent drop in VO2 when tested in turbid water (80 NTU) as did musse ls acclimated at lower turbidity (0 NTU).