Herring, Guinea creeks have high nutrient concentration

Center for the Inland Bays releases 3rd annual State of Your Creek
September 30, 2019

Story Location:
Camp Arrowhead
35268 Homestead Way
Lewes  Delaware  19958
United States

A recent study of Herring Creek and Guinea Creek in Sussex County shows average concentrations of nitrogen in both waterways is 10 to 12 times the healthy limit.

Released Sept. 16, as part of Delaware Center for the Inland Bay’s third annual State of Your Creek, the report said, in parts of Guinea Creek, low oxygen levels exacerbate nutrient pollution, creating areas where fish can’t survive and bacteria levels are not safe for swimming or shellfishing.

Dr. Marianne Walch, science coordinator for the center and lead author of the report, said high level of nutrients can lead to overgrowth of algae, poor water clarity and unhealthy conditions for fish and people.

Walch said there is no direct discharges into either creek, which means all the pollution runs off or through the land. These watersheds saw a 68 percent increase in development from 1992 to 2012, and have one of the highest densities of active septic systems of anywhere in the Inland Bays watershed, she said.

“It’s not a great situation,” she said.

Water quality data from several long-term monitoring locations were used to develop this report – two stations maintained by Delaware Department of Natural Resources and Environmental Control and two stations maintained by the University of Delaware Citizen’s Monitoring Program. 

Walch said another factor contributing to pollution in the creeks is loss of forest land and a high percentage of agricultural land. As the watersheds become more urbanized there are fewer forests and wetlands to help absorb pollution, she said.

Encompassing a 34-square-mile area of western Rehoboth Bay, Herring and Guinea Creeks are two freshwater sources. In addition to supporting wildlife, these creeks provide water access for a growing number of residents in the area.

The report shows that in the tidal portion of Guinea Creek, the concentrations of enterococcus failed to meet the single-sample safe swimming standards 83 percent of the time.

Enterococcus bacteria are found in the guts of all warm-blooded animals. DNREC uses enterococcus levels to determine recreational swimming advisories in Delaware, with the threshold beginning at greater than 104 colony-forming units per 100 milliliters.

Walch said a preliminary study by DNREC suggests the enterococcus in Guinea Creek are coming from wildlife, not human sources.

Center for the Inland Bays Executive Director Chris Bason said the Inland Bays creeks are extremely important to Sussex County because life on the water contributes to the tourism and real estate industries. He said work has been done over the years to clean them up the water, yet, he continued, they remain tarnished treasures.

Bason said Sussex County is doing a good job converting old septic systems to sewers, which should make a positive contribution to the health of the creeks, but there’s a lag time between the improvements on the land and seeing results in the water.

“The bottom line is that we have some serious water-quality issues, and there is a lot that we’re already doing and still need to do to address them,” said Bason.

The release of the report was done in conjunction with National Estuaries Week, Sept. 14 – 21, a nationwide celebration of bays and estuaries.

The Delaware Center for the Inland Bays is a non-profit organization established in 1994, and is one of 28 national estuary programs. The report was completed with researchers from the University of Delaware’s Water Resources Agency and is available at

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