Estuaries form transition zones between rivers and saltwater environments. On Cape Cod, where we have few, if any true rivers, estuaries are areas partially surrounded by land where ground water and/or marsh streams interface with coastal waters. Estuaries are tidal, brackish or slightly salty, and are often high in sediments. The mixing of sea water and fresh water provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world. Orleans is fortunate to have three major estuary systems:
- A set of three marshes off of Cape Cod Bay (Rock Harbor, Little Namskaket and Namskaket),
- Pleasant Bay – the largest estuary on Cape Cod, and
- Nauset Estuary / Town Cove.
Our estuaries provide nurseries and habitat for a large number of organisms, including fish, shellfish, terrapins, horseshoe crabs and eelgrass. They are highly productive growth environments. Migratory bird populations depend upon essential food sources in estuaries to fuel their migrations and in some cases to feed their young.
Unfortunately, similar to estuaries all over the world, Cape Cod’s estuaries are being impacted by a number of factors related to population pressure and human activities. Excessive nitrogen from septic systems and fertilizers is causing eutrophication which leads to increasing algae and plant growth. Other factors are man-made pollution from untreated storm water runoff, sea level and temperature rise from global warming, wetland and eelgrass destruction from all of these factors, as well as boating activities and near-shore construction. Since 2001 the Massachusetts Estuaries Project has been studying the Cape Cod estuaries and documenting the dire conditions including decreasing oxygen, increasing nitrogen concentrations, and declining marine life and plants (https://www.mass.gov/guides/the-massachusetts-estuaries-project-and-reports ). The conditions in Pleasant Bay are particularly well documented and illustrate the status of all the Orleans estuaries and the measures being taken to improve water quality.
For Pleasant Bay, it is expected that tide levels could see an increase of four to eight feet by 2100 due to sea level rise. If this occurs, the increase would result in considerable changes along the Nauset barrier beach and Pleasant Bay inner shoreline (https://pleasantbay.org/news-updates-2023 ).
Between 2000 and 2014 nitrogen levels, especially bioactive nitrogen, have increased in Pleasant Bay. Even with the 2007 break in the Nauset barrier beach in Chatham that created a new inlet and a significant increase in ocean water flowing into upper Pleasant Bay (and increased dissolved oxygen levels), the trend of increasing nitrogen concentration continues. By 2014, it was clear from all the measured parameters that things were getting worse. The Pleasant Bay Alliance reported on the declining water quality in Pleasant Bay and convinced the citizens of Chatham, Harwich, Brewster and Orleans that multiple steps needed to be taken:
By 2018, a Comprehensive Nitrogen Removal Plan for Pleasant Bay had been prepared with input from all the towns. Several different approaches were proposed as part of a State certified “Watershed Permit” to reduce the total nitrogen to acceptable limits ((https://pleasantbay.org/wp-content/uploads/PB-TWMP-final-4May2018.pdf). The Pleasant Bay Watershed Permit is the first of its kind in the State and as a result of this permit, Orleans and the three towns are exempt from the 2023 MA Department of Environmental Protection (DEP) regulations requiring all properties within areas determined to be nitrogen sensitive to install very expensive nitrogen reducing septic systems (called Innovative/Alternative Systems).
Instead, the Comprehensive Nitrogen Removal Plan focuses on eliminating septic systems, which are responsible for 75% of the controllable nitrogen load to the Bay. The major component of the plan is construction of new sewer systems in Orleans, Harwich and Chatham, and a new Wastewater Treatment Plant in Orleans. Each town operates independently, but their activities are coordinated in compliance with the plan. The new Wastewater Treatment Plant in Orleans has been operational since 2022. There is also a Wastewater Treatment Plant in Chatham which treats sewage from both Chatham and Harwich. Efforts have also been underway to reduce the use of lawn fertilizers as fertilizer accounts for approximately 16% of the nitrogen input to the Bay. Another effective intervention is oyster farming in Lonnie’s pond. Oysters (and shellfish in general) remove nitrogen as they filter it out of the water and use it to grow and develop. Changes in land management of the Captains Golf Course in Brewster are also being made to reduce the fertilizer (nutrient) inputs to the Bay.
In Orleans, the downtown commercial and private residential properties began connecting to the new sewerage system in 2023. Further installation of sewer pipes and connections is ongoing in a phased approach which will take decades to complete:
The result of the sewering and wastewater treatment will benefit not only Pleasant Bay, but all the estuaries and freshwater ponds of Orleans. The Association to Preserve Cape Cod (APCC) summarizes future expectations in the 2024 ‘State of the Waters’ report (https://capecodwaters.org/overview) as follows: “A number of towns have made significant steps toward managing nutrients by approving construction of modern wastewater treatment projects. While (estuaries and coastal) embayment water quality has yet to improve as a result, as these projects are implemented over the next few years, the region should begin to see lower nutrient loading that should be reflected in improving water quality”.