Environmental Controls of Dissolved Oxygen in Coastal Streams across USA.

Coastal stream water quality receives myriad inputs of upstream pollutants, which potentially create stress to aquatic life and ecosystem health. We analyzed the dominant spatiotemporal controls of dissolved oxygen (DO) for 105 stream monitoring stations across the Atlantic, Gulf, and Pacific Coasts of USA. The stream hydrology and water quality data were collected from USGS NWIS and EPA STORET databases. Land use/cover data were collected from the National Land Cover Database (NLCD). A systematic data analytics showed strong controls of redox drivers (pH, specific conductance) on stream DO in wet season across the Pacific and Atlantic coasts, suggesting domination of metabolic activity (e.g., microbial decomposition) and salinity. However, strong negative linkage of DO with stream temperature were evident across the coasts in the wet and dry seasons, suggesting domination of climatic controls. Solar radiation had positive linkage with DO across the Gulf and Atlantic coasts, indicating the well-known photosynthetic effect of plants in enriching DO. The built-up land was found to have a strong positive influence on stream DO across the Atlantic coast, indicating the dilution of pollutants during higher runoff. In contrast, built-up land had a negative linkage with DO in the dry season across the Gulf coast, indicating the adverse impacts of urban sewage and litters on stream water quality. Further, agricultural land had a strong negative linkage with stream DO in the wet season in the Gulf Coast, indicating the impact of nutrient enrichment on stream water quality by agricultural runoff. Interestingly, watershed slope had positive linkage across all coasts of USA. The quantified relative linkages of DO with the spatiotemporal drivers across U.S. coasts provide useful insights and useful information to achieve/maintain healthy coastal streams and ecosystems.