Water Quality

Save Our Sound’s Water Quality

Shallow coastal areas like Nantucket Sound are fed by estuaries and salt ponds and are essential to the health of our oceans because they support feeding and reproduction of many species. Indications of pollution in these ecosystems in terms of algae blooms and depletion in fish stocks are increasing and threaten this ecosystem. Dead and decaying algae has stretched for miles along the coastline of Nantucket Sound, releasing noxious gas noticeable along the coastline of the Sound. Parts of Florida and the Mississippi coast have closed beaches as a direct result of red tides and other harmful algae blooms.

Algae Blooms

The two runoff nutrients that increase algae blooms are nitrogen and phosphorus. Excess nitrogen comes from poorly treated wastewater and common fertilizers. Excess phosphorus generally comes from poorly maintained septic systems that leak it into surrounding groundwater that then enter ponds and lakes which threaten open ocean.

Local blooms are caused primarily by nitrogen coming from septic systems. High levels of liquid nitrogen in saltwater act as fertilizer and cause algae to grow dramatically. Through the continuous release of excess nitrogen and phosphorous from septic systems over the past few decades, we have been continually overfertilizing our waters. Blooms of sea lettuce and microalgae are on the rise as the result of this over fertilization of our local waters, known as eutrophication. These blooms choke the oxygen that these seaweeds and seagrasses need to grow and thrive.

Salt Marshes

Due to habitat degradation, there has been a decrease in natural systems like salt marshes. These systems help filter nutrients and run off from surrounding areas and prevent a significant amount of runoff from entering the ocean. Without a flourishing salt marsh system, run off and nutrients enter nearby waterways leading to the ocean, causing more frequent and prominent algae blooms, which can in turn have an effect on fish population and local aquatic flora and fauna. When there is an excess of nutrients entering the waterways, algae growth increases, which decreases levels of oxygen in the water, resulting in more acidic conditions. These acidic conditions can result in fish and other aquatic life dying as well as an impact in growth of eelgrass and other aquatic vegetation that is pivotal to the health of Nantucket Sound.

Algae blooms also pose a health threat to the surrounding community. When algae blooms are high, aquatic species feed on phytoplankton which may be toxic. Shellfish can consume these toxic phytoplankton which can then make them contaminated and toxic for humans to consume.

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