Thursday, November 15, 2012

Hypoxia in Long Island Sound

Hypoxia in Long Island Sound.
The colors represent the percentage of years that there was hypoxia in the
bottom waters of the Long Island Sound (1991-2011)
Image from the Long Island Sound Study.
Click for more information.
One of the major pollution problems in any water body near urban areas is nitrogen pollution from runoff.  Long Island Sound, particularly the western portion of the sound, has a serious nitrogen pollution problem that leads to hypoxia in some areas.  Hypoxia is a condition in the water where dissolved oxygen is reduced to the point that marine organisms are stressed and in some cases die.  The reason that oxygen is reduced in the water is complex.  You can read about it in detail here.  But, in short, algae thrives in the nitrogen-rich environment.  Algae blooms occur and create unnatural biogeochemistry in the water.  When the algae dies, the decaying process uses up disproportionate amounts of oxygen, thereby reducing oxygen levels for marine organisms.

There are a number of anthropogenic sources of nitrogen in Long Island, the most important being sewage treatment plant releases with storm water pollution the second most significant source.  Reductions of nitrogen in these sources are key to the overall health of the Sound.

No comments: