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.