Long Island Sound
Water Quality and Hypoxia Monitoring Program

Results and Annual Reports

A collage of LIS water quality monitoring pictures
LIS Monitoring Surveys
The summer Long Island Sound water quality sampling schedule includes routine water quality surveys as well as summer-only hypoxia surveys.

Routine water quality surveys are conducted year-round, including during the summer months.  During these surveys water samples are collected from 17 stations and analyzed for nutrients and other water quality parameters.  In addition, phytoplankton and zooplankton samples are collected from 6 stations in the Sound.

Hypoxia surveys are conducted during the months of June through September at an additional 30 stations.  During hypoxia surveys, stations are sampled for dissolved oxygen to get a more accurate understanding of the extent of summer hypoxia conditions in Long Island Sound bottom waters.

DEEP's Long Island Sound Water Quality Monitoring Program utilizes data from both surveys to monitor the extent of low dissolved oxygen in Long Island Sound bottom waters, or 'summertime hypoxia'.  Hypoxia condition maps are posted as soon as possible after each survey.  

Monitoring Schedule
Monitoring Results

This year's monitoring results are reported in the survey summaries and hypoxia maps below.   

Survey Summary Newsletters:

Dissolved Oxygen Distribution/Hypoxia Extent Maps:


Historic Monitoring Reports & Maps
Use the drop-down menu below to view and download available summary reports and maps from past monitoring efforts.

LIS Hypoxia Monitoring Distribution List

Biweekly newsletters, summarizing the results of each survey, are also distributed to interested parties. If you are interested in receiving future biweekly survey summary newsletters, email Katie O'Brien-Clayton at Katie.Obrien-Clayton@ct.gov to be added to the distribution list.

Photo of the research vessel John Dempsey
Long Island Sound
Water Quality and Hypoxia Monitoring Program
Content last updated December 2023.