Impacts of multiple interacting stressors on the environment: Investigating the fate, transport, and dynamic relationships between contaminant and nutrient cycles

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Water quality issues that lead to freshwater eutrophication are a rapidly intensifying global concern and the recent increase in eutrophic conditions in the Great Lakes has gained international attention. Elemental cycles, carbon regimes and metabolic processes are changing and we have little insight into the long-term effect these changes will have on large lake systems. The Great Lakes account for over 85% of North America's freshwater supply and have had a history of water quality problems that peaked in the early 1970's with cultural eutrophication in Lake Erie. Phosphate inputs were identified as a critical factor causing eutrophication that stimulated changes in environmental policies that led to a decline in eutrophication through to the 1990's. However, recent rises in cyanobacteria blooms provide evidence for the re-eutrophication of Lake Erie. Despite many coordinated efforts that attempt to link eutrophication to phosphorus dynamics, it is becoming clear that the magnitude and complexity of this issue has moved beyond a simple phosphate-limited mechanism.***Currently, progress has been made to improve our understanding of the fate and transport of contaminants (methane, hydrocarbons, industrial solvents and wastewater), natural organic matter (NOM), and nutrients (nitrates, phosphates, and sulfates); however, interpretations are often constrained by static' geochemical snapshots that limit unifying the dynamic relationships between individual chemical species and their changing behavior over time. Knowledge gaps exist connecting the historical deposition of nutrients, the recycling of carbon, nitrogen, sulfur, and phosphorus in soil and sediments, and their relationship to cyanobacterial biomass development across temporal and spatial scales. This research will use geochemical approaches (compositional and isotopic) to improve our understanding of the dynamic relationships between the fundamental processes that control the availability of C/N/S/P from terrestrial and aquatic sources (biotic and abiotic), and the adaptive metabolic responses that promote cyanobacteria growth in different environmental conditions. ***An understanding of the underlying mechanisms responsible for the fate and transport of C/N/S/P from point and non-point source emitters through to their final point of deposition (or metabolic uptake) will expose the causal links that drive primary production at each stage of the system and provide strategic targets to control eutrophication. A comprehensive understanding of the key chemical and environmental factors that influence the measurement, monitoring, and identification of pollution sources responsible for water quality issues will lead to better policy decisions and long-term protection of our freshwater resources.