Urban Pollution Increases Sensitivity to Temperature Changes in Elliptio complanata Mussels Exposed to Municipal Wastewaters

Abstract

The cumulative effects of pollution in the context of global warming are not well understood at the present time. The purpose of this study was to determine whether organisms exposed to urban pollution are more susceptible to temperature changes. Feral Elliptio complanata freshwater mussels were caged and immersed for 1, 12 and 24 days in the final aeration pond treating domestic wastewaters from a township with a population of about 25,000. Mussels were also placed in the river upstream from the township to serve as reference. Following each exposure times, mussels were collected for temperature-dependent mitochondrial electron transport (METT) activity assessments. Other biomarkers were used, including xenobiotic metabolism (cytochrome P4503A4, glutathione S-tranferase and metallothioneins), energy budget (MET at 20oC and total lipids) and gonad status endpoints (gonadosomatic index [GSI], lipid peroxidation [LPO] and vitellogenin-like proteins). The data revealed that mussels exposed to the aeration pond had elevated METT and MET activities, suggesting that they were more sensitive to temperature changes and spent more energy than the controls. METT activity was negatively correlated with lipid stores in gonad, pointing to a negative energy budget. METT activity was also influenced by all xenobiotic metabolism and gonad status markers, with the exception of GSI. This suggests that temperature sensitivity is increased in mussels exposed to urban pollution and involves the expression of xenobiotic biotransformation, oxidative stress and endocrine disruption.