We studied the estuaries of the U.S. East Coast and Gulf of Mexico to determine which coastal areas are most vulnerable to changes in nutrient input. We modeled the environmental and economic impacts of land-use changes to understand the water flow (hydrology) and nutrient runoff in these areas. These models will enable more accurate ecological forecasting and long-term planning for the protection and use of the nation’s estuaries.

Why We Care
Increases in nutrient inputs to U.S. coastal waters have led to substantial changes in these coastal ecosystems, with an estimated degradation of two-thirds of U.S. coastal habitats. Projected population growth, land development, and agricultural intensification suggest that nitrogen loading to these areas is likely to continue to increase. In 2000, the National Research Council called for additional efforts to identify coastal ecosystems that are most sensitive to nutrient enrichment, improve policies and technologies for reducing nutrient loads from land, and determine nutrient-pollution effects in estuaries.

What We Are Doing
We enhanced the models that predict nutrient enrichment vulnerability to include economic scenarios and outcomes. This will enable scientists and policymakers to more precisely determine how best to protect and restore vulnerable coastal ecosystems. Additionally, we included both watershed and nutrient inputs when considering the water (hydrological) cycle and current trends in land use to inform our analyses on short- and long-term ecological impacts.

Specifically, in this project we:

1. Refined and compared three existing models of environmental and economic effects of land use, nutrient management, and climate change on nutrient flux to estuaries. We developed more detailed databases than those currently available and used them to refine, compare, and apply three ecosystem models for Atlantic and Gulf of Mexico watersheds to assess the effects of climate change and land-use/land cover on nutrient delivery to estuaries.  Also, we conducted an economic analysis of the impacts of policy actions to relate potential load targets to their costs.
2. Developed a classification system of estuaries according to their susceptibility to nutrient enrichment. The classifications are based on the refined models. We are in the process of testing the models against an expanded NOAA data set.
3. Developed ecological indicators to explain variations among estuaries. We developed biological, physical, and morphological indicators of the effects of eutrophication on higher-level predators and to explain variations among estuaries. We identified these indicators from scientific literature and used models to make the indicators useful to explain upper-level animal responses to eutrophication.

The project team included partners from the University of Michigan’s School of Natural Resources and Environment, the Smithsonian Institution Environmental Research Center, Cornell University, and the United States Geological Survey.

Benefits of Our Work
The models will be used in two ways. First, the models will help identify the magnitude and types of species abundance changes that are likely to occur. Second, these models will help distinguish human fishing effects from those of eutrophication. The specific model results will be most applicable to Atlantic Coast estuaries with similar species and ecosystem structures as Chesapeake Bay, but can be used to help guide analyses elsewhere.

This work is intended to lead to a better predictive understanding of the potential causes and consequences of nutrient pollution on estuarine ecosystems and how estuarine hydrology and geology modify estuarine and upper ecosystem–level responses to nutrients.