Greenwich Free Press

NY - ONE WATER: Climate impacts on water resources. Putting it all together: water, climate change, and our coastline.

Climate change is rapidly reshaping Long Island Sound. Water temperatures in eastern Long Island Sound (LIS) have increased over the past four decades, four times faster than the global ocean.

Ocean acidification, another symptom of climate change, is also happening much more rapidly in LIS than elsewhere in the U.S. Cold water marine organism populations are declining. Sea levels are rising, increasing the frequency of flooding and erosion along our shorelines, which also impacts water quality in the Sound as it brings contaminants and sediments from onshore into the Sound.

Throughout the “One Water. Shared” series, we’ve looked into understanding where our water comes from, where it goes, and how to best steward this essential resource. In this final article, we look closely at our shoreline and LIS and how the health of the entire watershed depends on how we live on land.

Our Shellfish

A survey made by local commercial shellfishers calculated that Greenwich waters are the home to about twenty-five million oysters, close to one billion clams (hard and soft shell), and ten million mussels (blue and ribbed). An abundance of healthy shellfish in Greenwich waters and their natural filtration capabilities are a major factor in maintaining and improving water quality.

Nutrients, such as nitrogen and phosphorus, are essential for the terrestrial landscape, but an overabundance of these nutrients negatively affect Sound waters.  Too much nitrogen and phosphorus fertilizers runoff or seep into ground and surface waters, causing algae to grow faster than ecosystems can handle. Significant increases in algae harm water quality, food resources and habitats, and decrease the oxygen that fish and other aquatic life need to survive. Large growth of algae or “algal blooms” can severely deplete oxygen levels in the water undermining or killing off leading to illnesses and damage in fish populations. Algal blooms are also a risk to human health and can result in closed beaches.

Shellfish provide important services in the Sound ecosystem. Roger Bowgen, Shellfish Commissioner, says, “Each of these mature shellfish continuously filter the water they inhabit, removing algae, nitrogen and other contaminants. Daily filtration rates vary per species, e.g. oysters 50 gallons, clams 24 gallons and mussels 15 gallons. Based on the number of shellfish this calculates to billions of gallons of water being filtered per day. One estimate is that because of the number of shellfish in Greenwich Cove, it’s contained water is completely filtered twice a day.” A recent study by the National Oceanic and Atmospheric Administration (NOAA) determined that 9% of Nitrogen is removed from the Greenwich watershed annually by hard clam and oyster aquaculture, about 31,000 pounds of nitrogen per year. More than half of the local nitrogen input into Greenwich’s waters are from “nonpoint sources”, such as runoff from lawn fertilizers, which we learned from our previous article, “The Lowdown on Runoff: Keep Water Clean”.

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