Physicochemical and urban land-use characteristics associated with resistance to precipitation in estuaries vary across scales 

Abstract. Estuaries are subject to frequent stressors, including elevated nutrient loading and extreme hydrologic events, which impact water quality and disrupt ecosystem stability and health. The capacity of an estuary to resist changes in function in response to precipitation events is a key component of maintaining estuarine health in our changing climate. However, generalizable patterns in factors related to estuarine responses to extreme precipitation remain unknown. We investigate physicochemical factors and land-use characteristics that are associated with ecological resistance to precipitation – broadly defined as the magnitude of ecosystem change induced by an event – in five disparate estuaries distributed across the continental United States. Using long-term meteorological and water quality data from the National Estuarine Research Reserve System along with land use/land cover and population data, we examine relationships between the resistance index – a proxy for ecosystem stability calculated using dissolved oxygen – and physicochemical and urban land use characteristics on local-to-continental scales. Contrary to our initial hypothesis, we found that more urbanized estuaries were more resistant to precipitation events, and that water temperature, water column depth, turbidity, nitrogen, and chlorophyll-a were related to resistance on a continental scale. However, these trends interacted with estuarine salinity and varied across individual estuaries; where we found additional relationships of resistance with salinity, turbidity, phosphate concentrations, N:P, and tree cover. Considering emerging stressors from new climatic scenarios and from urbanization, these results are important for representing the impacts of disturbances in large-scale models and for informing management decisions regarding estuarine water quality.