Cedar Pond is a brackish pond with salt and fresh layers that do not mix, and which is subject to a constant addition of nutrients. The pond is in a highly eutrophic, unstable, and unhealthy condition. Sources of pollutants include nearby septic systems, stormwater runoff, and the hundreds of cormorants that roost on the power lines over the water surface. An old weir system which regulated tidal inflows from Rock Harbor has deteriorated and no longer controls the water level.
In recent years, stormwater systems on Route 6 and along Locust Road have been upgraded. The Town is working with NSTAR to identify a device that will prevent birds from roosting on the power lines. This spring, the Town is proposing a water quality study to evaluate how best to manage water exchange with Rock Harbor to provide the best opportunity for habitat restoration in the pond. The Annual Town Meeting will have an article to support the study cost of $40,000.
What are the most recent trends in Pleasant Bay’s water quality?
In an effort to better understand the trends in Pleasant Bay’s water quality, the Alliance contracted with The Cadmus Group to conduct a statistical analysis of ten years of water quality data collected throughout the Bay and its ponds. The Alliance was particularly interested in the effects of the Patriots Day storm of 2007, and the resulting “break” in Nauset Beach, on trends in water quality.
The Cadmus report showed that water quality is improving at some sites, but declining at others. However, most sites did not demonstrate any statistically significant trend. In general, those sites showing improvement in water quality tended to be located in the open water areas of the Bay, while those sites showing declining water quality tended to be located in ponds.
These results suggest that the increased exchange of water between the Atlantic Ocean and Pleasant Bay (as a result of the 2007 inlet formation) may be responsible for limited improvements in water quality in some open areas of the Bay. Even with limited improvement in these areas, the report found that bioactive nitrogen concentrations exceeded MEP modeled restoration values for estuarine health. The 2007 inlet is expected to migrate south along Nauset Beach. As it does, tidal flushing of the Bay may decrease to previous levels and nutrient concentrations may return to pre‐inlet concentrations if steps are not taken to reduce watershed nitrogen loads.