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The Problem with Nutrients
What’s at Stake?: Although much of the Buzzards Bay ecosystem remains relatively healthy, major changes in land use and nutrient loading from the surrounding watershed are resulting in significant changes in habitat health along the Bay coastline. This system-wide change involves nutrients, particularly nitrogen. At greatest risk are the Bay’s more than 30 harbors, coves and river mouths which receive the bulk of the nutrient load from the watershed. Unfortunately, it is these same embayments and nearshore waters that are least capable of handling excessive nutrients and support the most diverse ecological habitats and productive shellfisheries, as well as much of the recreational and aesthetic values of the Bay.
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| A healthy sign of a clean marine environment—lush green blades of eelgrass. (Photo: Joseph Costa) |
Nutrient Pollution Effects: Nutrients are a natural and essential part of all marine ecosystems. Excess quantities of nutrients (particularly nitrogen in Buzzards Bay), however, can adversely affect water quality and coastal habitat and ultimately impact a wide range of marine organisms including fish and shellfish populations. Similar to over-fertilizing your garden, nutrient overloading in marine ecosystems stimulates the growth of algae. Too much algae blocks sunlight to eelgrass, shading out this valuable nursery habitat and feeding ground. Living and dying algae consume oxygen, leading to hypoxic (low oxygen) and anoxic (no oxygen) conditions. This process of water quality decline creates a chain reaction of negative impacts known as eutrophication. Poor water clarity, bad odors, stressed marine organisms and even fish kills are all symptoms of eutrophic conditions.
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| An overgrowth of algae resulting from nitrogen pollution overtakes an eelgrass bed. |
Widespread Problem: Nutrient overloading, or eutrophication, is the greatest long-term threat to the Buzzards Bay ecosystem. While toxic impacts such as oil spills can have serious consequences, they tend to be relatively localized. The difficulty with managing nitrogen loading is its widespread distribution from a wide array of sources throughout the Bay’s 432 square mile watershed. The principal sources of nitrogen inputs to Buzzards Bay include septic systems, wastewater treatment plants, stormwater runoff, lawn and agricultural fertilizers and acid rain. All of these sources are rooted in the watershed’s ever-growing population which has more than doubled this century alone to now include 370,000 people.
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