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RARE Partnership Explores Delaware Estuary

EPA scientists and collaborators complete the first inventory and characterization of benthic communities in the Delaware estuary.

Researchers working in the Delaware estuary

The Delaware Estuary is home to a variety of bottom-dwelling (“benthic”) organisms that make up the base of the estuary’s food chain and are an integral part of its overall health.  As part of the Regional Applied Research Effort (RARE), scientists from EPA’s Office of Research and Development, EPA Region 2 and Region 3, the States of Delaware and New Jersey, The Partnership for the Delaware Estuary (PDE), the Delaware River Basin Commission, and Delaware and Rutgers Universities joined forces to conduct the most comprehensive benthic survey of the Delaware Estuary to date.

Estuaries are areas partially surrounded by land where rivers flow into the sea. They are fertile, biologically diverse places that provide a host of “ecosystem services,” such as flood and erosion control, and nursery habitat where many of the fish and shellfish that support the seafood industry grow.

The primary objective of the EPA partnership was to inventory and map the benthic communities across the Delaware Estuary and thereby enable the partnering states, non-profits, and federal government agencies to better align their protection and conservation efforts to sustain the Estuary’s health.

“The collaboration on this project was remarkable,” says EPA’s Renee Searfoss, the lead scientist for the survey. “Three different states were involved and there were a multitude of decisions to make, but we all worked together and successfully accomplished the project at hand.”

EPA funded much of the study and provided personnel and resources including the research vessel and equipment.  PDE provided extensive leadership and organization as well as technical support. Expertise and research assistance was contributed by various other organizations and many dedicated volunteers.

In the summer of 2008, researchers completed a ten-week survey of soft-bottom communities in the Bay.  Samples were collected from over 230 sites stretching along 91 miles of river.  At each site, biological samples and data on sediments and water conditions were taken.  A video of the water column and river bottom was also recorded at each site to further characterize the benthic environment.

Through the use of remotely operated vehicles and an EPA dive team, researchers came across unexpected “biological hot spots” in hard-bottom areas, home to an abundance of sponge and worm colonies.  Such biologically active areas are often the engines which drive the productivity of fisheries further up the food chain.

The effort was continued in 2009 with a focus on hard-bottom communities.  During this phase, freshwater mussel colonies were discovered outside an urban area of Philadelphia, including one species previously thought to be extinct.

Other surprising discoveries included the presence of wild celery and submersed aquatic vegetation (SAV) in shallow areas, previously not believed to be common in the estuary.

The RARE project has led to a better understanding of the ecosystem overall.  Long term goals for the use of study results include informing environmental managers, pinpointing important areas to protect or restore, determining correlations between physical biological and chemical factors in assessing the Estuary’s health, and establishing baseline data to use for future assessments.

Discoveries made over the course of the project have also served as impetus for new research.  Continued efforts will add more layers of data to the assessment that began with the RARE proposal. Planning for future research is in progress, and previously collected data is being analyzed and integrated to provide the most comprehensive understanding of the Delaware Estuary and how to best protect it.

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