Geochemical approaches to improve nutrient source tracking in the great lakes

Abstract

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. 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 1970s with cultural eutrophication in Lake Erie. Despite many coordinated efforts that attempt to link eutrophication to phosphorus, it is becoming clear that knowledge gaps exist in understanding nutrient dynamics and their relationship to cyanobacterial biomass development across temporal and spatial scales. New geochemical approaches (compositional and isotopic) can improve our understanding of the relationships between the fundamental processes regulating nutrient dynamics 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 nutrients 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 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.