Mortality, energy reserves, and oxidative stress responses of three native freshwater mussels to temperature as an indicator of potential impacts of climate change: A laboratory experimental approach.

Abstract

Due to rapid global climate change, the temperature of streams and rivers is predicted to be increased, influencing aquatic organisms, particularly bivalve species. To better understand their response to elevated temperature, three native species of freshwater mussels namely, Coelatura aegyptiaca, Mutela rostrata and Chambardia rubens were exposed for 21 days to four temperature treatments (18 - 25-30 and 35 °C). Mortality was recorded on a daily basis over the experiment. A variety of responses including biomarkers at the cellular level and whole organism level were examined in surviving organisms after 21 days. In response to exposure to thermal stress, three mussel species exposed to 35 °C showed 100% mortality after 21 days. However, exposure to 25 °C and 30 °C induced significant decreases in adenosine triphosphate (ATP) production and energy reserves (Protein, lipid and glycogen) compared to the control group maintained at 18 °C. Temperature-induced oxidative stress, indicated by the greatest reduction in total antioxidant capacity (TAC) and elevated levels of lipid peroxidation products. As energy generation decreased and oxidative stress increased, trends were for condition indexes (CI) and survival to decrease. In comparison, C.rubens has a higher thermal tolerance than C.aegyptiaca, and M.rostrata. The responses reported herein, along with the predicted rates of climate warming, indicated that freshwater mussels in the Nile River, Egypt will be negatively impacted by climate change and may incur significant losses in the coming years.