National Park Service

Northeast Temperate Network (NETN)

atmospheric deposition and stress


An estuary is a body of water formed where freshwater from rivers and streams flows into the ocean, mixing with the seawater. Estuaries and the lands surrounding them are places of transition from land to sea, and from freshwater to saltwater. Although influenced by the tides, estuaries are protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that surround them.

Importance & Issues

Estuary in BOHA The estuarine nutrient enrichment vital sign applies to Acadia and Boston Harbor Islands and was developed by the Northeast Coastal and Barrier Network as a component of the estuarine eutrophication monitoring protocol. The negative effect of nutrient enrichment in estuaries is well documented. Habitat quality can be adversely impacted from increased nutrient inputs, anoxic conditions can arise, and changes to the biotic community can occur. The Massachusetts Water Resources Authority (MWRA) has ongoing water quality monitoring within Boston Harbor and will provide adequate information for the Boston Harbor Islands. The NETN will determine what specific existing monitoring stations are relevant for the Boston Harbor Islands, how frequently these stations are sampled, and how to best establish an information exchange between NPS and MWRA. At Acadia, we will consider implementation of the NCBN estuarine eutrophication monitoring protocol or a subset thereof.

Monitoring Objectives

Monitoring objectives set forth by the NCBN for the estuarine eutrophication protocols are as follows:

Estuarine Eutrophication: Seagrass

  • Determine the distribution and abundance of submerged aquatic vegetation beds in selected areas of parks.
  • Determine long-term, inter-annual trends in seagrass condition (shoot density percent cover and biomass) in selected estuarine areas of parks.
  • Measure ancillary data, including Light Attenuation, Sediment Parameters, Temperature, and Salinity

Estuarine Eutrophication: Water Quality

  • Determine long-term trends in summertime levels of dissolved oxygen concentration, turbidity, attenuation of photosynthetically active radiation, temperature, salinity and suspended chlorophyll concentrations in estuarine waters and organic carbon in estuarine sediment in selected park sites.

Estuarine Nitrogen Loading

  • Determine long-term trends in nitrogen loading estimations to park estuaries through nitrogen load modeling that incorporates human population density, atmospheric, fertilizer and wastewater nitrogen sources, non-point source discharge permits, permitted water withdrawals for domestic and agricultural consumption, fertilizer consumption and livestock population data.


Measures set forth by the NCBN for the estuarine eutrophication protocols are as follows:

Estuarine Eutrophication: Seagrass

The trend in submerged aquatic vegetation (SAV) distribution and condition over time offers an indicator of changes in nutrient load, while also providing information directly applicable to critical habitat protection efforts.

Estuarine Eutrophication: Water Quality

Diagnose local causes of nutrient enrichment, detecting changes in nutrient loads, and determine if nutrient inputs are near to exceeding thresholds that would result in shifts in ecosystem structure and function.

Estuarine Nitrogen Loading:

Monitor estuarine nutrient agents of change, or potential sources of nitrogen within the watersheds of each of the parks.



Last Updated: December 30, 2016 Contact Webmaster