to Reduce Harmful Hypoxia in Long Island Sound
The TRBP Floating
Workshop IX took place on June 12, 2009. It was planned to
coordinate with and compliment The Last Green Valley's
Sea, Connecting the Drops in The Last Green Valley events. It
featured a tour of the Thames River aboard
Project Oceanology's Envirolab
and focused on upland contributions of nitrates to the waters of Long
Island Sound. Click
here to view a
slide show of the workshop.
Nitrates are the leading
cause of seasonal hypoxic conditions in Norwich Harbor, part of the
Thames River estuary and in western Long
Island Sound. There are actions municipalities can take to reduce the
upland contribution of nitrates. Select examples were featured on
the Thames River tour.
was developed based on the results of a
Municipal Survey conducted in 2009.
Long Island Sound is an estuary, or a
place where freshwater from land runoff combines with sea water in a
semi-enclosed area. Estuaries are normally highly productive
habitats. However, in parts of Long Island Sound and in
Norwich Harbor, seasonal hypoxia (low dissolved oxygen) in deep water
habitats place stress on marine organisms. Swimming
organisms, such as fish, can leave the area. Bottom dwelling
organisms, such as shellfish and marine worms, may be stressed or killed
due to the lack of available oxygen.
The major cause of hypoxia in Long
Island Sound is nutrient enrichment, especially in the form of nitrates.
Near the surface, where solar exposure is high, phytoplankton thrive in
the nutrient enriched water. Upon death, they settle to the
bottom where they are decomposed by oxygen consuming decomposer
organisms. Once the dissolved oxygen concentrations fall
below 5 mg/l, mild adverse ecological effects
in the bottom water habitats of the Sound begin to occur. According to
Island Sound Study the most severe effects (such as mortality) occur
when dissolved oxygen levels fall below 1.5 mg/l at any time and below
3.5 mg/l in the short-term (i.e., 4 days).
The major sources of nitrates to surface waters in
The States of Connecticut and New
York are cooperatively working to achieve a
Total Maximum Daily Load for nitrates in order to meet water quality
standards and improved habitat quality in Long Island Sound.
This workshop was
funded in part by the
and Wildlife Foundation as part of the Long Island Sound Study.