Long Island Sound
Water Quality and Hypoxia Monitoring Program

Results and Annual Reports

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

• 2023 LIS 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:

• August 2023 Hypoxia Survey (HYAUG23) Map - August 14 & 16, 2023
• August 2023 Water Quality Survey (WQAUG23) Map - July 31 - August 3, 2023
• July 2023 Hypoxia Survey (HYJUL23) Map - July 17-19, 2023
• July 2023 Water Quality Survey (WQJUL23) Map - July 5-10, 2023
• June 2023 Hypoxia Survey (HYJUN23) Map - June 23, 2023

• June 2023 Water Quality Survey (WQJUN22) Map - May 31 - June 2, 2023

Historic Monitoring Reports & Maps