Threat: Nitrogen Loading

Nitrogen Loading

What & Why  Nitrogen is a nutrient that is essential to life in the estuaries. However, scientific understanding of estuaries is that high levels of nitrogen may cause problems like the excessive growth of plants and algae. When the plants dies, oxygen needed by fish is pulled out of the water and can cause fish to suffocate. The rapid plant growth can also shade or smother underwater eelgrass meadows and other important habitats, limiting important functions such as providing food and shelter and cleaning the water. Excess nitrogen is a problem across the US and around the world.

Non-Point Source Pollution  Nitrogen enters the Great Bay Estuary primarily in two ways. First, nitrogen from fertilizers on lawns and farms, septic systems, animal wastes, and air pollution or atmospheric deposition from the whole watershed is carried into the bay through rain and snowmelt runoff, river flow, and groundwater flow this is called non-point source pollution. These sources account for 68% of the nitrogen entering our system.

Point Source Pollution  Second, there are 18 municipal sewer treatment plants that discharge treated wastewater out through pipes either into the bay or into rivers that flow into the bay, this is called point-source pollution. This nitrogen loading section looks at the recently released NHDES Great Bay Nitrogen Non-Point Source Study and breaks it down by subwatershed, it only charts the non-point sources of nitrogen entering the bay. For more detailed graphs of non-point source pollutant loads by town, source and pathway please read the NHDES Great Bay Nitrogen Non-Point Source Study.

Land conservation is the least expensive and most effective action to preventing water pollution and supporting healthy ecosystems. As of 2015 municipalities in the region have conserved 14% of land in the Piscataqua Region. For a more detailed look at conservation review the land conservation plans for NH and ME.

Percentages indicate pounds of nitrogen per year.


[HC.JS:cocheco-watershed,pie,Cocheco River Watershed,Nitrogen Load] [HC.JS:exeter-squamscott-watershed,pie,Exeter–Squamscott River Watershed,Nitrogen Load] [HC.JS:hampton-seabrook-watershed,pie,Hampton and Seabrook Watershed,Nitrogen Load] [HC.JS:lamprey-river-watershed,pie,Lamprey River Watershed,Nitrogen Load] [HC.JS:oyster-bellamy-watershed,pie,Oyster–Bellamy River Watershed,Nitrogen Load] [HC.JS:salmon-falls-watershed,pie,Salmon Falls River Watershed,Nitrogen Load] [HC.JS:winnicut-coastal-watershed,pie,Winnicut and Coastal Watershed,Nitrogen Load]

PREP is part of the U.S. Environmental Protection Agency’s National Estuary Program, a joint program between local, state and federal agencies established under the Clean Water Act with the goal of protecting and enhancing nationally significant estuarine resources. PREP is supported in part by an EPA matching grant and is housed within the School of Marine Science and Ocean Engineering at the University of New Hampshire.

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