Collaborative Effort & Oysters Key to Corsica River Recovery

In 1996, the Maryland Department of the Environment (MDE) added the Corsica River in Queen Anne’s County to its list of impaired waterways. The problem? Algal blooms and other water quality issues were proving detrimental to aquatic life, and also limited recreational use of the river.

Today, the river is on the mend, the result of the implementation of the Corsica River Watershed Restoration Action Strategy (WRAS). Behind the strategy, an ongoing effort now in its eighth year, is a partnership between the Town of Centreville, the Corscia River Conservancy (CRC), the Queen Anne’s County Soil Conservation District, and other local partners, with management support by the the Maryland Department of Natural Resources (MDNR) and MDE.

The Corsica River’s three subwatersheds are part of the Corsica River Watershed Restoration Action Strategy (WRAS).

“The effort to restore the Corsica has required careful planning and the perseverance of local citizens, state and local government, and our partners in agriculture,” explained Frank DiGialleonardo, a Centreville resident who has long worked as a volunteer on the restoration of the Corsica watershed. “It’s remarkable what we have all been able to achieve together.”

Monitoring data from the river show significant improvement in nutrient loads of nitrogen and phosphorus, specifically in the nontidal tributaries of the Three Bridges Branch and Gravel Run subwatershed. Improvements are likely the result of a confluence of practices implemented through the WRAS, which are ongoing, and include:

• Increased use of cover crops by farmers;
• The implementation of other agricultural best management practices;
• Multiple significant urban storm water infiltration projects, and;
• Upgrades to Centreville’s Waste Water Treatment Plant.

The Corsica River action strategy has been a success from the start. After the EPA put its stamp of approval on it in 2005, it was highlighted as one of the nation’s best watershed plans at an annual Clean Water Act meeting. The same year, the governor chose the Corsica project for the state’s targeted restoration watershed program.

According to DiGialleonardo, despite the success of the project, the Corsica still faces challenges. “We continue to struggle with excessive nutrients that lead to too much algae and reduced water clarity needed for a healthy river ecosystem.”

How to continue to improve the Corsica? One of the answers might be oysters.

The Corsica was one of the first watersheds to partner with DNR in its Marylanders Grow Oysters program. Waterfront property owners are essentially gardening oysters in order to protect them during their vulnerable first year of life. Once sufficiently mature, they are planted on local sanctuaries, or oyster reefs, where they can play a role in filtering nutrients from the Corsica.

Oysters sampled at the Corsica Reef. Photo by Chris Judy, who is responsible for the MGO program at the Maryland
Department of Natural Resources (DNR).

“Oysters are among the most effective tools in improving water clarity,” said DiGialleonardo. “Each oyster can filter up to 50 gallons of water per day. CRC is glad to be partnering with DNR to restore a historic oyster bar on the river.”

Sampling of the oyster reef by DNR indicates this approach is working so far, a boon for the Corsica and all who rely on it. While the impact of placing caged oysters in the river is limited compared to more intensive oyster reef restoration, the success of the MGO program may help pave the way toward future large scale projects in the Corsica.

Additional information about the oyster restoration program in the Corsica, including a short video, can be found at corsicariverconservancy.org and below. A recently published report about general progress with the watershed restoration project can be found there as well.

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