DEEP: Hypoxia and Monitoring Fact Sheets

Hypoxia and Monitoring Fact Sheets

Hypoxia is a condition of low dissolved oxygen concentrations in the waters of Long Island Sound that impacts up to half of the Soundís waters each summer.  The primary cause of hypoxia is nitrogen enrichment that comes from a variety of sources throughout the Long Island Sound watershed, in particular sewage treatment plants, stormwater runoff and atmospheric deposition.  The nitrogen stimulates the growth of phytoplankton, microscopic plants that grow in the Sound.  Today, so much nitrogen has been added that the amount of phytoplankton generated causes low oxygen in the summer when it decays in the bottom waters.  To more fully understand hypoxia and its effects on water quality and the biology of Long Island Sound, CT DEEP receives funding from the EPA Long Island Sound Study to monitor the Soundsí waters year round.  In addition to taking measurements of dissolved oxygen from New York City to Block Island Sound, CT DEEP measures nutrients (nitrogen, phosphorus, silica), phytoplankton and other related physical and chemical conditions.

Annual summary reports of the Long Island Sound Hypoxia Season Review - Summer Water Quality Monitoring Program are listed below.  Click on any one of these report links to view detailed data and narrative information of water quality conditions for the summer.  For the 2014 Hypoxia Summary we have also produced a GIS StoryMap showing specific water quality data by station location.  When viewing the map you may click on any station point to view a window with detailed information such as surface and bottom dissolved oxygen as well as temperature, salinity and latitude/longitude coordinates.

Monitoring 2018 Long Island Sound Hypoxia Season Review, CTDEEP & IEC Joint Report - (PDF)

Monitoring 2017 Long Island Sound Hypoxia Season Review, CTDEEP & IEC Joint Report - (PDF)

Monitoring 2016 Long Island Sound Hypoxia Season Review, CTDEEP & IEC Joint Report - (PDF) 

Monitoring Long Island Sound 2015 - (PDF)

Monitoring Long Island Sound 2014 - (PDF)

Monitoring Long Island Sound 2013 - (PDF)

Monitoring Long Island Sound 2012 - (PDF)

Monitoring Long Island Sound 2011 - (PDF)

Monitoring Long Island Sound 2010 - (PDF)

Monitoring Long Island Sound 2009 - (PDF) 

Monitoring Long Island Sound 2008 - (PDF) 

Hypoxia 2004 - (PDF)

Hypoxia 2002 - (PDF)

Hypoxia 2000 - (PDF) 

Summer Hypoxia Monitoring Survey, 1991-1998 Data Review - (PDF)

  LIS Water Quality Program & Info

Last updated September 6, 2019