Bay-bottom Inventory

 

When the Partnership for the Delaware Estuary (PDE) convened its first-ever Delaware Estuary Science and Environmental Summit in 2005, scientists and resource managers identified and prioritized the scientific needs of the Delaware Estuary. One of these needs was a better understanding of "benthic communities" in both Delaware Bay and its surrounding tidal rivers.

Estuarine benthic communities are groups of organisms that live in or on the bottom of tidal waterways. Examples include oysters, seagrasses, and the many tiny animals that live inside sediment. These organisms play a crucial role in estuarine food webs; a role that affects hundreds of fish and shellfish species that use the estuary for feeding, spawning, and rearing their young. These communities furnish "ecological services," or tangible benefits like improved water quality and sediment quality. Hard-bottom reef communities even serve as rich habitats, and they protect adjacent shorelines from waves and erosion.

     
It may not look like much, but this vile of mud and others like it will be used to map the habitats of the Delaware Estuary’s tiniest creatures, which, altogether, make up the base of the region’s food web.

 It may look like modern art, but this is one of many sponges discovered in July of 2008 by University of Delaware researchers during a DEBI survey in Delaware Bay

The Delaware Estuary Benthic Inventory was launched during a workshop in March of 2007 in an effort to examine these communities. The ideas and vision for the DEBI prompted the U.S. Environmental Protection Agency (EPA) to identify resources for this work through its Office of Research and Development's Regional Applied Research Effort. Since that time, the PDE and EPA have worked closely with representatives from approximately 10 academic, federal, nonprofit, and state institutions to devise a field-sampling strategy.

The objective of the DEBI is to catalog and describe the species living within the benthic ecosystem of the tidal Delaware River and Bay. These data will be used to add biological information onto detailed maps previously created by the states of Delaware and New Jersey. Findings from the DEBI will show the extent of underwater plants, animals, and environmental conditions, including species or habitats of special concern.

The DEBI will not only provide scientists and managers with a field guide for the bottom of the estuary, but it will also help them evaluate its health by:

  • examining biological integrity
  • identifying areas in need of protection
  • identifying areas in need of restoration
  • helping us understand where different species congregate
  • helping us understand the relationships between species and the food web

An estuarine survey was initiated in July of 2008 using the research vessel Lear, which is owned and operated by the EPA's Region 3 Office. Over a two-month period, scientists sampled more than 230 locations across 91 river miles between the mouth of Delaware Bay and Philadelphia. Most locations had a soft bottom and were sampled using a device called a bottom grab. Other locations required a new approach.

During the survey, EPA and PDE staff worked with Dr. Doug Miller and his team from the University of Delaware to explore deep-water communities living on hard bottoms, which are not easily sampled using traditional methods. The team focused on the Broadkill Slough northwest of Lewes, Delaware. Dredging and first-hand accounts by EPA divers led to the discovery of extensive sponge communities that appear to form complex habitats across at least a mile of the bay's bottom. More sampling of these and other hard-bottom areas is needed. Some follow-up surveys are planned for the summer of 2009 in hard-bottom areas of Delaware, New Jersey, and Pennsylvania.

Samples collected from targeted benthic communities in the Delaware Estuary are yielding valuable data concerning:

  • species that are present (most notably "macroinvertebrates," or worms and bugs) and their biomass
  • associated "ecosystem services" provided by these animals
  • water-quality conditions
  • sediment chemistry
  • sediment grain size
  • sediment containing PCBs, or polychlorinated biphenyl ethers (pending analysis by the Delaware River Basin Commission)

Results of the DEBI will be released through this PDE website as they become available.

For more information on the Delaware Estuary Benthic Inventory, please contact Angela Padeletti at (800) 445-4935, extension 103, or APadeletti@DelawareEstuary.org.