Oysters grow in clusters to form great reefs, protecting themselves from predators and providing habitat for other species.
Iconic Oyster Oysters grow in clusters to form great reefs, protecting themselves from predators and providing habitat for other species. ©: Erika Nortemann / TNC

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Oyster restoration in the Chesapeake Bay

The Chesapeake Bay marked a major milestone in 2015 with the completion of the world’s largest oyster restoration project at Maryland’s Harris Creek.  Now a recent study, funded in part by The Nature Conservancy, shows the benefits from investing in large-scale oyster restoration.

Our native oyster does a lot more than get served in restaurants.

BIGGER THAN THE NATIONAL MALL

Oyster restoration has long been a priority for The Nature Conservancy.  Oysters filter sediment and algae and remove nitrogen and phosphorus—harmful pollutants in excess—from the water, while their reefs provide nurseries and feeding grounds for rockfish, crabs and other commercially and recreationally important species.

Recent and dramatic changes in the public policy arena, coupled with emerging scientific understanding and the creation of large-scale oyster sanctuaries, are providing a clear path forward to restore this keystone species.

Section of restored oyster reef in Harris Creek, Maryland.
Harris Creek Section of restored oyster reef in Harris Creek, Maryland. © Smithsonian Environmental Research Center

At 350 acres, the Harris Creek reef is bigger than the National Mall and was seeded with more than 2 billion oysters. These oysters were bred at the University of Maryland's Horn Point Hatchery, where they were selected for their resistance to dermo (Perkinsus marinus) and MSX (Haplosporidium nelson), two diseases that have decimated oyster populations over the last 60 years.

The 2016 Oyster Reef Monitoring Report, released by NOAA, indicates that Harris Creek’s reefs are highly successful. Data and analysis show that 97% of those reefs met the requirements for oyster density (at least 15 oysters per square meter) and biomass when they were monitored in 2016.

The 30 oyster reefs studied, totaling 90 acres, were constructed in Harris Creek in 2013.  Following the plan for the Harris Creek restoration, each restored reef will be monitored at three years, and again at six years, after restoration.

As a tributary of the Choptank River, Harris Creek eventually flows into the Chesapeake Bay, where oyster populations are at a tiny fraction of their historic levels. Recognizing their value to Bay health and the economy, in 2014 the states of Maryland and Virginia—in partnership with the federal government and private industry—renewed their commitment to restoring oysters to the Bay. Harris Creek is one of five Maryland tributaries and 10 baywide targeted for restoration as part of that effort.

Piankatank River Oyster Recovery Project partners signed pieces of granite as part of a 2017 dedication ceremony for a newly constructed 25-acre oyster reef.
Oyster Restoration Rocks! Piankatank River Oyster Recovery Project partners signed pieces of granite as part of a 2017 dedication ceremony for a newly constructed 25-acre oyster reef. © Patrick Bloodgood / U.S. Army photo

Quantifying the Benefits

A study released in 2018 aimed to understand the ecological impact of the Harris Creek restoration and quantify its benefits.

Using a new web-based computer model, the Virginia Institute of Marine Science (VIMS) and the University of Maryland Center for Environmental Science (UMCES) estimated the water filtration and nutrient removal capacity of the restored Harris Creek oyster sanctuary reefs. Among the highlights from the study’s findings:

  • The restored reefs are able to filter the full volume of Harris Creek in less than ten days during summer months. 
  • Based on collected data, the restored reefs have the potential to remove one million pounds of nitrogen from the Chesapeake Bay over a decade.
  • The water filtration benefits of the reef are provided by more than the oysters.  Mussels and tunicates living on the reefs contribute more than 40% of the total filtration.  

The study shows that oyster restoration is an important and cost-effective addition to the suite of approaches that make up Bay recovery efforts. What makes this such a smart investment is not just the role oysters can play in water quality, but also the numerous co-benefits that come with a healthy reef.

Reefs can take the punch out of storm waves and help slow the rate of erosion along marsh edges.  As they grow, oyster reefs accrete vertically, keeping pace with sea level rise and increasing their capacity for storm protection.

The study was led by VIMS researchers Lisa Kellogg and Mark Brush, and UMCES researcher Jeff Cornwell. The study was funded by The Nature Conservancy, the Oyster Recovery Partnership and the National Oceanic and Atmospheric Association (NOAA).

The model, developed by Brush, is available online for anyone to use.  Placing this type of decision-support tool directly into the hands of resource managers creates the potential for application around the Bay and in other estuaries.

By restoring and repopulating large oyster reefs in key parts of the bay, we hope to reach a tipping point where oyster populations become sustainable, expanding their numbers and the benefits they and their reefs provide.

Oyster restoration is an important and cost-effective addition to the suite of approaches that make up Bay recovery efforts.

  • Harris Creek Study

    (5.29 MB PDF)

    Quantifying the ecosystem benefits of large scale oyster restoration in Maryland's Harris Creek.

    DOWNLOAD
  • Oyster Reef Monitoring Report

    (71.74 MB PDF)

    Analysis of data from a survey of the Harris Creek reef restoration site three years post completion.

    DOWNLOAD
  • Harris Creek Restoration Model

    An online decision making tool that simulates water quality, ecosystem dynamics and function of restored oyster reefs. Use the Model