USGS Eastern Ecological Science Center Estuary Science Highlights
National Estuaries Week, September 20-27 this year, is an annual celebration to raise public awareness about the importance of estuaries, the dynamic ecosystems where rivers meet the sea, and the vital services they provide. Estuaries support rich biodiversity and are essential for recreational activities, economic growth and community wellbeing.
The Chesapeake Bay is the largest estuary in the United States, where freshwater from rivers mixes with saltwater from the Atlantic Ocean, creating a rich and productive ecosystem.
The USGS Eastern Ecological Science Center provides comprehensive science supporting the health and resilience of the Chesapeake Bay through research on invasive blue catfish including both removal strategies and contaminant assessments; advanced modeling to better understand fish health, particularly in smallmouth bass; studies of salinity patterns throughout the bay evaluations of how wetland sediment additions influence elevation and ecological function at places like Blackwater National Wildlife Refuge; and monitoring of wildlife indicators of bay health such as osprey reproduction.
These interconnected efforts help resource managers protect ecological integrity and guide conservation across the Chesapeake Bay watershed.
Let’s explore some of the USGS science that helps estuaries stay healthy and thriving.
Monitoring Wetland Elevation and Recovery After Sediment Addition at Blackwater National Wildlife Refuge
USGS Eastern Ecological Science Center researchers are helping track marsh recovery at Blackwater National Wildlife Refuge by monitoring elevation change and collecting long‑term data across sediment‑addition sites. Blackwater, one of the Chesapeake Bay’s largest brackish wetland complexes, has faced major marsh loss over the past century due to sea level rise, invasive nutria, low sediment supply, and marsh fragmentation.
To help stabilize the marsh and improve habitat for species like black rail and saltmarsh sparrow, the U.S. Fish and Wildlife Service used thin‑layer sediment placement at Shorter’s Wharf in 2016 and 2017. USGS monitoring found that added sediment compacted at an average of 4.5 mm per year, with initial elevation targets met at most sites before later compaction and sea level rise reduced some of the gains. A second sediment‑addition effort at Back Garden began in 2026 with higher target elevations informed by lessons learned.
Ongoing surveys, photos, and LiDAR (Light Detection and Ranging) will continue to document how the marsh responds, supporting future management decisions.
Evaluating Blue Catfish Status and Removal Strategies in Recently Invaded Tributaries of the Chesapeake Bay
USGS Eastern Ecological Science Center researchers are evaluating potential removal strategies for invasive blue catfish through coordinated data collection and modelling efforts with state, federal, and academic partners. This work is focused on developing tools and information that support long-term, adaptive management across the Chesapeake Bay, especially in Maryland waters.
Researchers are developing a population model that projects blue catfish dynamics under current conditions and alternative management strategies. This population model integrates multiple sources of information, helps guide monitoring efforts, and supports decision making about removal strategies to reduce harmful impacts of invasive blue catfish.
Ultimately, the work of USGS Eastern Ecological Science Center and its partners informs a broader science strategy for blue catfish that maintains a healthy Chesapeake Bay ecosystem and the diversity of benefits it provides to our communities.
Salinity levels in the Chesapeake Bay
USGS Eastern Ecological Research Center researchers are investigating rising salinity in Chesapeake Bay watershed streams and what it means for stream health. Just as you don’t expect salty water from your home faucet, freshwater plants and animals have adapted to live within a certain range of salt levels. Exposure to unusually salty water can harm fish, aquatic insects, and other organisms that support stream food webs in waterways that flow into the Chesapeake Bay. Across the watershed, monitoring sites show increasing trends in stream salinity, but gaps in monitoring coverage make it difficult to understand where salinity is rising fastest and why. USGS research is modeling nearly 40 years of salinity conditions to clarify patterns across seasons, years, and environments. The work evaluates how land cover, soil and rock characteristics, and human activities affect salinity levels.
These models can help identify where natural geology has the strongest influence versus where human-related sources may be increasing salinity. The findings can also help guide actions such as reducing road-salt use, improving stormwater management, and protecting forested areas that help reduce salty runoff to streams. This work equips resource managers with targeted strategies to keep the freshwater flowing to the Chesapeake Bay making the bay a little less salty and a lot healthier.
Osprey Reproduction on the Chester and Choptank Rivers
USGS Eastern Ecological Science Center researchers and partners work across the Chesapeake Bay to monitor osprey nests, track breeding success, and collecting long-term data on the nesting activity.
Since the ban of DDT (dichlorodiphenyltrichloroethane), Chesapeake Bay osprey numbers have grown from about 1,450 breeding pairs in the early 1970s to more than 8,000 pairs by 2020. The strongest recovery has occurred in the Bay’s fresher, low-salinity waters.
Starting in the late 1980s, ospreys breeding in the saltier parts of the southern Chesapeake began showing signs of food shortages. Ospreys depend almost entirely on fish, and in high‑salinity areas they especially rely on menhaden. When menhaden and other fish are more difficult to find, osprey parents struggle to feed themselves and their young. Over time, apparent food shortages have led to widespread brood loss in many parts of the Bay, except in low‑salinity areas where a wider variety of fish is available.
Other factors like weather, predators, disease, and water quality also play a role, but declining prey availability appears to be the main cause of poor reproduction in high‑salinity regions.
USGS scientists are continuing to analyze 2025 data and actively monitored nests in 2026. Using cameras at nests, we are identifying the fish species brought to chicks and estimating how often parents deliver food. These observations help us understand where prey shortages are happening and how they may affect the future of the Chesapeake Bay’s osprey population.
Learn more about USGS osprey research.
Smallmouth Bass as Sentinels of Watershed Health
USGS Eastern Ecological Science Center researchers are using a multi‑endpoint ecoimmunology approach to reveal how streamflow, agricultural chemicals, and land use shape the health of smallmouth bass in Chesapeake Bay tributaries. A three‑year, four‑site study across the Potomac and Susquehanna Rivers shows that immune responses in bass act as early‑warning signals of ecosystem health and can be used to detect watershed stress before disease occurs.
By tracking immune biomarkers, researchers found that pesticide pulses during periods of unusual high or low flow, and local landscape inputs were the strongest drivers of fish immune variability across the study sites. Sites with more agriculture and development showed suppressed immunity and higher parasite burdens, while fish in forested streams had healthier immune profiles.
By reducing stressors that compromise immune function—like pesticide runoff and unpredictable changes in streamflow—decision makers can help decrease mortality rates, reduce observations of external disease, and support higher abundances of smallmouth bass across multiple size classes. Restoring riparian buffers also improves stream quality, allows these habitats to act as a sink for agricultural runoff, and protects fish health. Healthy streams support healthy fish and together, they support more resilient Chesapeake Bay ecosystems.
Understanding Contaminants in Blue Catfish
Increased harvest of blue catfish in the Mid‑Atlantic region has raised concerns as recent studies show these fish may carry detectable levels of Per- and polyfluoroalkyl Substances (PFAS) and other contaminants, including heavy metals, Polychlorinated biphenyls (PCBs), and microplastics. PFAS compounds like perfluorooctane sulfonic acid (PFOS) have been found in blue catfish and other species at concentrations exceeding safe human exposure levels. Measuring these contaminants in catfish blood and filets is crucial for evaluating risks to people, wildlife, and the environment.
This research is especially important for estuary health, as contaminant‑laden fish can reflect broader water quality issues and influence ecosystem stability, food‑web dynamics, and restoration goals. With blue catfish increasingly consumed or repurposed for feed and fertilizer, understanding contamination levels supports safe public consumption, informed species management, and stronger environmental protection across the region. Learn more about contaminants in blue catfish.