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Boston Harbor and Massachusetts Bay
MWRA Environmental Quality


Nutrients, like nitrogen and phosphorous are familiar to many people as ingredients in lawn and garden fertilizers. Nutrients are essential to the normal growth of plants in the ocean, but an excess of nutrients can be damaging. In marine environments, an overabundance of organic material and of nutrients, especially nitrogen, can lead to a condition called eutrophication, or over-enrichment of the system. Symptoms of eutrophication can include blooms of nuisance phytoplankton, discoloration of the water, bad odors, depression of dissolved oxygen in the water and sediment, shading out of seagrasses, and reduction of biodiversity in bottom-dwelling animal communities.

Since the transfer of Deer Island flows offshore, the amounts of nitrogen and phosphorus entering the Harbor have been greatly reduced. The Harbor is now returning to a more natural level of enrichment.