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NC - Clear—Not Just Clean—Water Matters for North Carolina’s Coast

As state commission prepares to set water clarity standard, a look at what it means and why it’s important

Seagrasses and other underwater plants, known as submerged aquatic vegetation (SAV), grow only in shallow estuarine waters rather than in deep water. Like plants on land, these marine flora—which provide critical habitat for economically important fish species and help protect coastlines and communities from shoreline erosion—need sunlight to grow.

In recent years, however, scientists and managers focused on the health of North Carolina’s coastal ecosystems have increasingly found that much of the 298 square miles of SAV in the state’s coastal rivers, creeks, and sounds aren’t getting enough light to thrive. Though the waters are shallow, they simply are not clear enough for the sun’s rays to penetrate. So, state leaders are now considering setting standards for water clarity to help restore and protect the health of SAV and the diverse ecosystems these plants support.

Last year, as part of its updated Coastal Habitat Protection Plan, North Carolina identified restoring and maintaining the state’s historical expanses of SAV as a key goal. State managers prioritized SAV because it supports abundant and diverse coastal fisheries that are essential to many of North Carolina’s economic sectors and, together with salt marsh, protect the state’s coast against rising sea levels and strong storms by anchoring barrier islands, absorbing wave energy, reducing erosion, and safeguarding human life and property.

For all these reasons, creating a standard to maintain water clarity and help SAV grow should be a priority for everyone who loves North Carolina’s vibrant and beautiful coast and who relies on it for their livelihood.

The color shows the cause

Clear water allows ample light to reach plants

When a coastal body of water is healthy and the substances that float or flow in it are balanced at natural levels, the water is typically visibly clear, allowing plenty of light to reach seagrasses and other underwater plants and supporting a robust ecosystem. However, changes to the usual color of a water body can indicate that certain substances—most often natural ones—are too abundant and are blocking light from reaching SAV.

When water is bright green, it’s usually a sign of an overgrowth of algae

Although some algae belong in a healthy ecosystem, high algae concentrations, known as a “bloom,” can block so much sunlight that underwater plants cannot survive. Algae blooms often result from an overabundance of two key nutrients—nitrogen and phosphorous—getting into the estuary when stormwater causes fertilizers used on farms, golf courses, residential lawns, and other landscaped areas to wash into streams, rivers, and sounds.

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