By Dave Kellam, New Hampshire Estuaries Project

The New Hampshire Estuaries Project (NHEP) has released a comprehensive water quality report that analyzes data from a wide range of sources on key indicators of water quality such as toxic contaminants, bacteria concentrations, and nitrogen loading for New Hampshire’s estuaries.

NHEP Coastal Scientist Phil Trowbridge developed the report that was peer reviewed by a team of water quality experts. Trowbridge reports that “the overall condition of the water in the State’s estuaries is generally good compared to estuaries across the country; however, conditions are changing. Some of the changes are for the better but more of the trends are troubling.”

Toxic contaminants, such as lead, zinc, DDT and PCBs, are a constant concern; however, the several indicators included in the report suggest that concentrations of these harmful substances are on the decline. Monitoring efforts have shown that shellfish tissue samples (mussels, clams, oysters) have toxic contaminant concentrations below national guidance values. Since shellfish collect toxic contaminants in their flesh when they feed, low levels of contaminants in these creatures suggest the ambient toxic contaminant levels are relatively low. Data from the past eleven years suggest that toxic contamination levels are decreasing.

In addition to shellfish tissue assessments, estuarine sediments also are analyzed for contaminant levels. Trowbridge says the data reveal few areas of contaminated sediments, which may be a surprise to some. “Given the industrial history of the area, many people believe that all of New Hampshire’s estuaries are contaminated. This is not true.” Sediment contamination is most significant in tidal rivers, most notably in the Cocheco River, near historically industrial areas.