Studying Organisms and Estuaries
Virginia Engle | EPA Ecologist

Virginia Engle explains the “benthic index” to EPA Administrator Stephen Johnson.

The National Coastal Assessment is a partnership between EPA, coastal states and other Federal agencies which completed assessments of all U.S. estuaries during 2000-2007 to survey the condition of our nation's coastal resources. This partnership was formed due to the need for nationally comparable data to determine the condition of our nation’s ecosystems.  Types of data include water column parameters, sediment chemistry and toxicity, benthic communities, demersal fish and tissue contaminants.  Two National Coastal Condition reports have been published, and a third report is scheduled for publication in 2008.

One study included in National Coastal Assessment in 2007 was the “benthic index.” Benthic organisms are small animals (such as clams and crustaceans) that live in or on the bottom sediments in water bodies.  Because they don’t move very far, if at all, during their life spans, they are good indicators of the environmental conditions in the area from which they were collected.

Low diversity and abundance of organisms like the benthic organism, or prevalence of pollution-tolerant species, can indicate the conditions in the water are poor. The design of the NCA program is probabilistic, which means that it can be used to estimate what percentage of the nation's waters are in good, fair or poor condition.

Virginia Engle is an ecologist within EPA’s Gulf Ecology Division at the National Health and Environmental Effects Research Laboratory.