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Keeping an Eye on Coastal Waters
By Pat Burke
May, 2006
The aquatic food web can be a complex and fragile system. For example, too few plankton (tiny plants and animals that drift in the water column) can lead to decreased populations of larger animals farther up the food chain; on the other hand, too many plankton can eventually interfere with oxygen levels and even decrease the amount of sunlight reaching aquatic plants-making it tough on plants and wildlife alike.
The right amount of nitrogen is key. An increase in nitrogen in estuaries and other coastal waters often creates blooms of planktonic algae, which in turn, can lead to low oxygen or even no oxygen in bottom waters (what scientists call "hypoxia" or "anoxia," respectively). This is due to the decomposition of the nitrogen-stimulated algal blooms.
Increasing our understanding of these cause-and-effect relationships is essential to determining manageable pollution limits for coastal communities.
Aquatic Food Web
Under the Clean Water Act, the U.S. Environmental Protection Agency (EPA) protects and restores the integrity of the nation's waters. To that end, the EPA's Atlantic Ecology Division (AED) is positioned at Narragansett, Rhode Island to provide critical research information on the environmental effects of manmade stressors-such as excess nitrogen from the atmosphere, wastewater, and fertilizers-on the estuarine waters of the Atlantic seaboard.
Researchers participating in AED's Aquatic Stressors Nutrient Research Program are gathering data on how estuaries respond to excess nutrients in the water. These data can be extrapolated from well-studied areas and used to accurately estimate effects in areas where less data are available.
AED research scientist Jim Latimer describes this work as a "comparative systems approach" that involves assessments of multiple components (such as bottom dwelling organisms, plankton, and rooted plants) in estuaries that receive nitrogen in low to high amounts.
Latimer explains how EPA researchers are using novel, efficient methods to measure the effects of nitrogen. These include using aerial digital photography to measure submerged aquatic vegetation and shipboard based digital photography to assess sea-bottom response to low dissolved oxygen.
One of the most exciting new tools at their disposal is an airplane-mounted hyperspectral scanner that can be used for quick surveillance of a wide array of ecosystem conditions. These regional results will feed into national and international efforts to develop effects-based nitrogen criteria and to assess the state of estuarine conditions.
By evaluating water quality indicators of low oxygen, food web conditions, and submerged aquatic vegetation in multiple embayments along the Connecticut, Rhode Island, and southern Massachusetts coasts, researchers will be able to use a wide range of data to construct models to help local environmental managers limit nitrogen releases to levels that maintain or improve the environmental quality of estuaries.
"Our job is to provide data, models, and methods useful to state and national stakeholders in their efforts to develop nitrogen limits protective of the environment," says Latimer.
Featured Scientist Jim Latimer | Author Pat Burke
Editor Aaron Ferster