Hows The Water

5.2.12 Start of the Season

Friends of the Bay started our water quality monitoring season on a beautiful Monday, April 16.  The first two runs of the season had to be cancelled due to small craft advisories on April 2 and 9.  The 16th was a beautiful day to start off the season, with unseasonably warm temperatures.  It was a pleasant contrast to many other early April days which were cold, wet and windy.

Friends of the Bay volunteers help to monitor the dissolved oxygen content, water temperature, salinity content and clarity of the water at nineteen different sites throughout the Oyster Bay/Cold Spring Harbor estuary.  In addition, we take water samples at each of these sites which are then tested for coliform bacteria on a weekly basis, and monthly for nitrogen.

Dissolved Oxygen (DO) levels are often used to gauge the overall health of the aquatic environment.  When the DO levels are too low (a condition called hypoxia) to non-existent (anoxia) the survival, reproduction, or use of an area by marine life is impaired.   There is a cyclical fluctuation in DO levels over the course of our water quality monitoring season, which runs from the first Monday in April to the last Monday in October.  During the spring the DO levels are generally high and as the air and water temperatures increase the DO levels can drop to 1.0 or below in August.  When September comes with cooler nights and increased rainfall, the readings increase again.  This is an established pattern, but if the DO levels begin to fall too quickly, or do not rebound in the fall, it could be an indicator that the water quality has become impaired.

Nitrogen is a necessary nutrient in a productive ecosystem, but too much nitrogen fuels the excessive growth of planktonic algae.  The dense algal blooms cloud the water and shade the bottom.  When the algae die and settle to the bottom, they are decayed by bacteria, a process that uses up available oxygen.  This can contribute to low oxygen levels in the water, which will then affect the marine life.

Coliform bacteria levels are used as an indicator of possible presence of human pathogens within the aquatic environment.  High levels of coliform bacteria can cause the closure of shellfish beds and swimming beaches due to health concerns.

This Week’s Results

DO: The Dissolved Oxygen readings were high this week, with levels of 9.0 or greater in all the areas.

Wildlife: All the osprey nests are fully occupied.  It appears there may be more ospreys than there are nests.  We saw many egrets and a few herons.  There was  a lingering flock of about ten brant near Seawanhaka.  The other winter bird species have apparently moved on.


Our water quality monitoring season began on April 16th and will continue until the end of October!  If you would like to become one of our water quality monitoring volunteers, are interested in other ways of assisting in our effort to preserve and protect the waters of the Oyster Bay/Cold Spring Harbor estuary, or want to report an activity that may be threatening the estuary/watershed please visit us online at or give us a call at 516-922-6666.  Friends of the Bay’s mission is to preserve, protect and restore the ecological integrity and productivity of the Oyster Bay/Cold Spring Harbor estuary and the surrounding watershed.