Top image:  View of Manorhaven Beach from the water while sampling on June 5, 2023
The Manhasset Bay Protection Committee, with the support of the Town of North Hempstead and the Nassau County Department of Health, maintains an annual water quality monitoring program.  This is meant to track the status of the Bay and set a baseline for progress to be measured against.  

2026 Water Quality Monitoring Season

The 2026 monitoring season started on Monday, June 1st.  Bacteria counts are provided by the Nassau County Department of Health and will be uploaded here as they are received.
​2026 Manhasset Bay bacteria data to 8-10
Slideshow images:  MBPC

Past Water Quality Monitoring Seasons

2025 Manhasset Bay bacteria data
​2024 Manhasset Bay bacteria data 
2025 Manhasset Bay in situ parameters (forthcoming)
2024 Manhasset Bay in situ parameters (forthcoming)
​A report on the 2023 monitoring season is currently being reviewed and is expected fall 2026.  Check back here for updates.

Past Reports

2016 through 2021 Manhasset Bay Water Quality Report (link to folder)

Funding for the 2016--2022 water quality monitoring program and reports was provided for by the New York State Environmental Protection Fund as administered by the New York State Department of Environmental Conservation.  ​Additional support was provided by the Town of North Hempstead and Nassau County Department of Health. 
​2009 - 2015 Water Quality Report
Older reports and data can be found at:  manhassetbayprotectioncommittee.org/PDF_PUBLIC/Water_Quality_Data/

Other Sampling Programs

The Interstate Environmental Commission (IEC) conducts summer water quality surveys in western Long Island Sound, including three stations in Manhasset Bay.  2025 marks the 35th consecutive summer of this monitoring.  Their survey summaries and data are posted in our files:  IEC surveys.  
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IEC’s final Western Long Island Sound data is publicly accessible and available to download via the USEPA’s Water Quality Portal up to December 2025. To request data via the Portal, use the Advanced Search, select the Project ID: “WLIS (STORET),” and select the Data Profile, "Sample Results (physical/chemical metadata)." Data downloads can be filtered with a desired start and end date.
The Connecticut Department of Energy and Environmental Protection (CT DEEP) performs various Long Island Sound water quality cruises throughout the year.  Their data is available on UCONN ERDDAP and the water quality portal (Org ID: CT_DEP01_WQX).  ​Their newsletters are posted in our files. 
  • In their summaries, "HY" signifies a “hypoxia” cruise where they only conduct water column profiles and collect grab samples for chlorophyll analysis. These are only conducted during the summer months (June-September). 
  • "WQ" signifies a “water quality” cruise where they collect samples for nutrients, BOD, OA parameters, as well as water column profiles.  Theses are conducted year round.
  • They sample 17 fixed stations year round. During the summer months they add another ~23 stations but only collect water column profiles. 
In March 2025, a new Satellite Ocean Color data portal was launched to explore, discover and download satellite imagery of three water quality indicators for Long Island Sound and NY/CT coastal waters.  This new satellite data portal was developed by the NY/CT Sea Grant-funded 2023 project, "Actionable satellite water-quality data products in LIS for improved management and societal benefits."  Questions regarding the Ocean Color Data Portal and project should be addressed to Dr. Maria Tzortziou.