Estuaries are one of the most vulnerable and degraded environments on Earth. They are impacted by anthropogenic stressors, including pollution and run-off from storm-water that alters natural chemistry and productivity. The latter can impact dissolved oxygen levels. Layered on top of anthropogenic pressures is climate change. Reduced rainfall means less freshwater input and increased stratification. A hotter climate means warmer waters, which have a reduced capacity to store dissolved oxygen. Together, the impacts of anthropogenic stressors and climate change increase the risk of estuarine fish experiencing hypoxia. Ample oxygen is crucial for fish health and reproduction.
My study assesses how the combined effects of increasing temperature and reduced dissolved oxygen affect Eastern blue-spot gobies from populations varying in proximity to urbanization. Fish were housed at 1 of 3 temperatures (15˚C, 20˚C, and 25˚C), placed in respirometers, and exposed to declining levels of O2 (80% to 10%). Metabolic performance and critical PO2 of each fish was measured and compared across a heavily urbanized and a natural population. I will discuss my results in light of the combined threat that climate change and urbanization pose for estuaries, and explore whether long-term hypoxic exposure confers greater resistance to these conditions in the future.