Environmental stressors: Pathways of exposure and aquatic invertebrate response.

摘要

The need to monitor freshwater and detect impairments prior to observable impacts is crucial to maintain species diversity and ecosystem function. Therefore, understanding the contribution of various matrices (i.e., sediment and water) to chemical exposure is critical for remediation of impacted sites.;To evaluate various matrices of chemical exposure, I focused on the organic pollutant polychlorinated biphenyls (PCBs) due to their relatively ubiquitous nature, high toxicity, and adverse effects on humans and wildlife. In complementary laboratory and field experiments, I compared the effects of aqueous versus sedimentary exposure of PCBs on invertebrates. In the laboratory, organisms exposed to PCB-contaminated sediments experienced greater mortality than those exposed to PCB-contaminated water and in the field experiments those closer to the sediments experienced greater mortality than those near the surface demonstrating the importance of evaluating toxicity at the sediment-water interface.;Beyond identifying the location of highest chemical exposure, it is important to monitor a protective endpoint that can indicate impacts before notable damage occurs. Oxidative stress (OS) can be used as a sub-lethal physiological impairment that if identified can indicate an environmental stressor prior to species losses. I examined OS and its potential role in stressor tolerance using two invasive mussel species, Dreissena bugensis and D. polymorpha. Mussels were evaluated for OS via lipid peroxidation and catalase activity following exposure to four stressors (e.g., high densities, temperature, hypoxia, and PCBs) both alone and in combination. Dreissena bugensis had a stronger OS response than D. polymorpha in single stressor conditions (p < 0.050); however, in multiple-stressor treatments D. bugensis had increased oxidative damage and was less tolerant to additional stressors. My results establish a correlation between tolerance to environmental stressors and oxidative stress in invertebrates, and demonstrate that D. bugensis competitive tolerance may come at the cost of the ability to respond to additional stressors via the antioxidant response. This study advances the ability to monitor aquatic systems. It identifies the sediment-water interface as an area of greater chemical exposure than surface waters and presents a novel and sensitive assay that can detect stressors early in the impact stages and help predict changes in aquatic communities.