Since 1986, NOAA’s Mussel Watch Program has monitored the nation’s coastal waters for chemical contaminants and biological indicators of water quality. The program has evolved to include the assessment of nearly 600 chemical contaminants, including metals, legacy organic compounds, and contaminants of emerging concern (CECs). In 2025, Mussel Watch collected Crassostrea virginica and Mytilus edulis samples from a network of 79 sites in the U.S. coastal northeast. Study results will support a better understanding of the sources, fate, and transport of contaminants in the region and will fill important data gaps for local stakeholders.
Why We Care
The immense upwelling of nutrients and the combined productivity of seaweed, salt marsh grasses, and phytoplankton make the Gulf of Maine one of the world’s most productive ecosystems supporting a vast array of organisms, including some of great economic importance. Growing coastal populations combined with industrial and residential development have contributed contamination to the gulf through wastewater and industrial effluent discharges, septic system releases, and storm water runoff. Additionally, the Chesapeake Bay is the largest estuarine system in the continental United States, with a watershed that covers over 64,000 square miles over parts of six states and provides critical habitats for wildlife and important fisheries. However, centuries of land development and agricultural and industrial activities have degraded water quality in the bay and its tributaries as a result of toxic chemical pollution, extensive sedimentation, and hypoxic (low oxygen) conditions.
Thousands of chemical contaminants from many point and nonpoint sources accumulate in the U.S. coastal northeast region every day, compromising water quality, which, in turn, threatens human and ecosystem health. Previous studies in the region have investigated legacy contaminants, such as trace elements and persistent organic pollutants (e.g., polychlorinated biphenyls (PCBs), organochlorine pesticides, chlordane, and polycyclic aromatic hydrocarbons (PAHs)). These research and monitoring efforts have helped managers limit the impact that legacy contaminants have on coastal ecosystems, but such efforts are lacking for the increasing number of new and unregulated compounds known as contaminants of emerging concern (CECs), many of which are known to be harmful to people, animals, and the environment. In response to resource managers’ concerns about the extent and impact of these chemical stressors, both ongoing and new, the Mussel Watch Program conducted a basin-wide survey to assess the magnitude and distribution of a suite of CECs, metals, and legacy contaminants in the U.S. coastal northeast region in 2025.
What We Are Doing
The Mussel Watch Program was established in 1986 and is a national chemical contaminant monitoring program housed in NOAA’s National Centers for Coastal and Ocean Science (NCCOS). The program uses an ecosystem-based approach to monitoring, which entails measuring the concentration of chemical contaminants in sediment and tissue of indigenous bivalves, such as oysters and mussels, as a way to evaluate local environmental quality. Bivalves are used as indicator organisms for chemical contaminants in their local environments because they are immobile and they bioaccumulate contaminants in the water as they filter feed up until the point at which they are reflective of the concentrations in the surrounding environment. Mussel Watch currently analyzes sediment and bivalves for both legacy contaminants and contaminants of emerging concern (CECs). Legacy contaminants have been monitored within the Mussel Watch Program since 1986 and include compounds such as chlordanes, chlorobenzenes, dichlorodiphenyltrichloroethane (DDT), dieldrins, endosulfans, hexachlorocyclohexanes (HCHs), butyltins, PAHs, and PCBs. The monitoring of CECs began in 2009 and includes contaminants such as alkylphenols, alternative flame retardants, current-use pesticides, (per- and polyfluoroalkyl substances (PFASs), polybrominated diphenyl ether (PBDEs), polybrominated biphenyls (PBBs), and pharmaceuticals and personal care products. In general, CECs are minimally regulated, not commonly monitored, but potentially toxic chemicals that are finding their way into the environment.
In 2025, the Mussel Watch Program assessed a network of 79 sites in the U.S. Northeast to be analyzed for the full suite of metals, legacy contaminants, and CECs. In this survey, 6 samples of Crassostrea virginica and 73 samples of Mytilus edulis were collected across the region, which spans from the Gulf of Maine through the Chesapeake Bay. Sites were selected based on recent success of historic site locations and availability of collaborator support in the region. Additionally, site selection was conducted in collaboration with natural resource managers from the Gulf of Maine Council on the Marine Environment and involved a strategic mixture of sites that met both programs’ monitoring needs. Mussel Watch designed the 2025 U.S. coastal northeast region chemical stressors survey in collaboration with the Gulfwatch Contaminants Monitoring Program.
Benefits of Our Work
This study supplies much-needed data to the national Mussel Watch Program and to local stakeholders and managers in the U.S. Northeast and informs water quality data used by coastal resource managers to develop effective, long-term policies to protect ecosystem services provided by the region.
