Eutrophication is the overabundance of nutrients in a body of water that results in harmful algal blooms, fish kills, and in some cases ecosystem collapse. We used the Assessment of Estuarine Trophic Status (ASSETS) model to determine the causes and status of eutrophication and expected future conditions in 141 U.S. estuaries and coastal water bodies in the early 2000s.
Why We Care
Eutrophication is among the most serious threats to the function and services supported by coastal ecosystems. Attempts to reverse coastal eutrophication have centered on reducing land-based sources of nutrients, such as fertilizer applications and wastewater treatment plant discharges. Periodic updates of eutrophication status are important in order to determine whether management measures are working to reduce water quality problems.
What We Are Doing
This national assessment used the Assessment of Estuarine Trophic Status (ASSETS) model to determine the causes and status of eutrophication and expected future conditions in 141 U.S. estuaries and coastal water bodies in the early 2000s. Results show that the majority of U.S. estuaries (65 percent) are moderately to highly eutrophic due to high nitrogen loads. Systems that have high residence times are more likely to become eutrophic. Comparison to assessment results from the early 1990s shows little change in conditions. Several waterbodies outside the U.S. were also evaluated and show a similar gradient of problems.
Benefits of Our Work
The assessment showed that conditions in the U.S. are similar to conditions in waterbodies across the globe, suggesting that management measures that work elsewhere could also work in U.S. systems. We also showed that there is still work to be done to reduce eutrophication. Management measures are working to hold the line against worsening conditions, but conditions continue to be moderate to highly impacted by nutrients in the majority of U.S. estuaries. These results will help guide future management measures.
We are hoping that we will be able to make another update of conditions in U.S. estuaries to show the status and changes that have occurred from the early 2000s to the early 2010s. However, such an update is dependent on funding, which to date has not been available.