ORLEANS — For more than 15 years, townspeople have been taking the fate of their estuaries into their own hands.
They've done this literally, by diligent collection of water samples from Nauset Marsh/Town Cove, Upper Pleasant Bay, Rock Harbor, and Namskaket and Little Namskaket marshes. The data were used by the Massachusetts Estuaries Project (MEP) to assess the health of these water bodies and played a part in establishing state regulatory limits for nitrogen, known as TMDLs (total maximum daily loads).
Recently, the Coastal Systems Group of the School for Marine Science and Technology (SMAST) at UMass Dartmouth reviewed the data and found that the consistent sampling protocols and testing stations that produced them will allow the information to be used not only to manage the restoration of the resources but also to meet state compliance standards. The review also looked at changes in the systems since the MEP assessment and the need for more comprehensive data related to changes in water column readings.
The report by Brian Howes and Ed Eichner of SMAST was reviewed last month by the town's marine and fresh water quality committee, which includes some of the people who have been monitoring local waters for more than a decade. More than 50 volunteers are involved in this summer's testing program.
Nauset Marsh/Town Cove, Pleasant Bay, and Rock Harbor have been identified as systems impaired by excessive nitrogen, but the data show the Namskaket marshes “as having healthy habitat systems with the capacity to accept additional nitrogen loads from their watersheds,” according to the report. A nitrogen-reduction TMDL has been developed by DEP for Pleasant Bay but not yet for the other impaired systems.
The report describes Namskaket Marsh as a 200-acre tidal salt marsh that receives floodwaters from Cape Cod Bay and watershed inputs from Orleans and Brewster. The MEP assessment showed “healthy salt marsh habitat throughout its tidal reach” and found that nitrogen loads could be increased by more than 200 percent. Findings were similar for 124-acre Little Namsaket Marsh, whose watershed inputs come only from Orleans. The watershed nitrogen load to this overall system could be increased by up to 65 percent.
The other systems have their challenges. Rock Harbor, an 80-acre salt marsh that receives tidal flood water from Cape Cod Bay with watershed inputs from Orleans and Eastham, also gets water discharged from Cedar Pond. The MEP assessment found healthy salt marsh on the upper portion of the system but “significantly impaired conditions” in the harbor basin. At the time of the assessment, Cedar Pond was brackish; since then, the tidal exchange has been increased and Cedar is now a salt pond. The town is working to restore the brackish conditions and the system's ability to reduce nitrogen levels.
The Nauset Marsh/Town Cove system, fed by tidal flood water from the Atlantic and watershed inputs from Orleans and Eastham, is healthy salt marsh habitat near Nauset Beach, but there is “significant impairment in each of the enclosed tributary basins,” especially Salt Pond and Town Cove. While the overall watershed nitrogen reduction target is 47 percent, the report calls for “additional site specific data” focusing on those two basins.
Pleasant Bay estuary, “the largest embayment on Cape Cod,” includes “numerous tributary subembayments such as The River complex, Paw Wah Pond, Quanset Pond, Pochet, Round Cove, Muddy Creek, and Bassing Harbor,” the report notes. The Orleans portion includes the northern region of the main bay plus all subembayments of The River system, including Arey's, Lonnies and Meetinghouse ponds.
The estuary's status ranges from “healthy to severely degraded,” according to the report, with the most significant impairment in locations including Meetinghouse, Arey's and Lonnies ponds as well as Round Cove and Bassing Harbor. The telltale signs are low dissolved oxygen, high phytoplankton biomass, macroalgal accumulations and surface mats, eelgrass loss, and impaired benthic animal communities. The overall reduction target for the estuary is 36 percent.
Orleans is on track to do its share for meeting nitrogen reduction targets with a planned combination of wastewater collection and treatment and innovative options such as nitrogen removal through aquaculture and permeable reactive barriers.
The report found that data collected by the town volunteers were amassed following proper protocols and will be a useful resource in helping to determine when the goals of the nitrogen reduction efforts have been met.