At UHI, we help coastal communities develop harbor management plans which provide a road map for management of municipal waterways and coastal areas. The topics addressed by these plans are identified by each community through interviews, workshops, surveys, and other types of research. The topic of water quality is always a key aspect of a harbor management plan. Many coastal communities are often trying to balance water and land uses with water quality protection, as the well-being of a coastal community depends on good water quality. 

Many factors can influence water quality including flushing and circulation, density of development and types of land-use along and within a watershed, and activities on the water. Today many coastal water bodies are affected by pollution from a variety of sources which can threaten the natural marine ecosystem and activities the harbor supports. 

Why a waterway’s connection to the open ocean matters 

Coastal harbors and waterways vary in shape and size, and are influenced by the geography of the land, with some having protection from barrier beaches and/or islands (Figure1a), and others more exposed to the open ocean (Figure 1b). Additionally, the entrance to a waterway can be wide or narrow. Together, these features impact water circulation and the amount of tidal flushing, which is the exchange of water (changing tides) between an enclosed waterway and the open ocean. Subsequently, the amount of tidal flushing can directly influence pollution levels. A waterway with more exposure to the open ocean (Figure 1b) experiences a higher rate of tidal flushing and increased water circulation, which can assist with flushing pollutants, compared to more protected harbors with narrow entrances, where pollutants are more likely to build up overtime (Figure 1a). 

A satellite image of a city and a body of water Description automatically generated

Figure 1. Nantucket Harbor (A) is an enclosed harbor with a single and narrow opening to Nantucket Sound. Provincetown Harbor (B) is less enclosed with a wide opening to Cape Cod Bay. 

Where do pollutants come from and how can they impact the marine ecosystem? 

Waterways can be polluted by excess nutrients, chemical contaminants, and biological contaminants (e.g., fecal coliform). Common sources of pollution include stormwater runoff, fertilizers, wastewater from septic systems, and land- or ocean-based marine debris. 

  • Excess nutrients, especially nitrogen, from failing septic systems and the over application of fertilizers, are a major problem affecting many waterways in Massachusetts. This leads to harmful algal blooms and depletion of dissolved oxygen in the water column, which can create anoxic (low or no oxygen) environments that result in decreased survival of marine life. For coastal communities reliant on fishing, this can directly affect both commercially and recreationally important species. 
  • Fecal coliform contamination from improperly managed wastewater can pose health risks to waterway users including boaters, kayakers, swimmers, and others. Many beaches in Massachusetts experience closings to swimming due to elevated fecal coliform levels. 
  • Manufactured chemical contaminants included in household and consumer products, cleaning supplies, building materials, etc. can enter waterways through stormwater runoff, outfalls, and groundwater outflows. These chemicals can bioaccumulate, or build up, in marine species, leading to biomagnification in the food chain.  
  • Most marine debris originate from land-based trash that is improperly managed. Other marine debris comes from offshore activities such as fishing, recreational boating, and shipping. Man-made materials such as plastic are especially concerning because they do not break down naturally in the environment and can persist for many years. 

Water pollution in many waterways will be influenced by climate change. More frequent heavy precipitation, increased flooding, and sea level rise is expected to lead to more stormwater runoff and pollution from wastewater through inundation of treatment plants or properties with septic systems. Additionally, warming ocean temperatures can act as a catalyst for algal blooms and bacterial growth.  

Protecting water quality 

Identifying and understanding where sources of pollution originate from is essential to determining prevention and mitigation strategies. This can be done through regular surface water quality monitoring, especially of heavily used areas such as a harbor, and testing for contamination in local commercial harvested species such as shellfish. Many coastal communities will employ education initiatives and outreach campaigns on pollutants from human sources to increase awareness and inform community members of individual prevention measures. Additionally, municipalities can develop and enforce local bylaws and regulations such as fines for illegal dumping, regulating the use of fertilizers, requiring dye tabs on boats with bathrooms, and other strategies. 

For more information on water quality issues and harbor planning, view the harbor plans in our current and completed projects online.