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Scientists Study How Well Shellfish Clear Muddy Waters

ALTAMONTE SPRINGS, FLORIDA — June 26, 2009 — Scientists in Florida and across the East Coast are looking to shed new light on whether restoring oyster reefs helps improve the clarity of water, benefiting seagrasses and other aquatic life. 

This week, teams of researchers installed hundreds of light sensors near natural and restored oyster reefs in the Mosquito Lagoon and Loxahatchee River to measure light levels around oyster reefs. The group included scientists from The Nature Conservancy, the University of Central Florida, the Loxahatchee River District and the National Oceanic and Atmospheric Administration (NOAA). The Nature Conservancy also plans to install light sensors at its shellfish restoration sites along Virginia’s Eastern Shore and New York’s Great South Bay

“Lots of folks have shown that in a lab or even a plastic bucket oysters can quickly improve water quality and clarity, but few people have measured it directly on any scale in the field,” said Rob Brumbaugh, the restoration director for The Nature Conservancy’s Global Marine Team. “This is the first time this particular approach has been tried, and we hope it provides a new method and direction for oyster restoration and research.”

Brumbaugh hopes the light sensors will provide further evidence showing that oysters clear the water as they feed on microscopic plants that grow in the bay. If so, water clarity will be greatest closest to the oyster reefs. Sensors have also been placed in areas that have sandy bottoms and no reefs to compare the water clarity away from oysters. He hopes that additional direct measurements will encourage people to consider oyster reefs valuable not just for harvests but for the other natural benefits or ecosystem services that they provide. 

Globally, 85 percent of shellfish reefs have been lost, according to a recent study led by The Nature Conservancy. Shellfish reefs and beds are essential to the health of marine ecosystems, yet they are almost always solely managed for harvest rather than habitat, according to the report.

In the Loxahatchee River, oysters were once widespread, but the system of reefs has declined dramatically over many decades, said Bud Howard, water resources director for The Loxhatchee River District.

“This river is a real jewel. It is one of two federally designated wild and scenic rivers in Florida,” Howard said. “Oysters play a key part improving water quality and in the life cycle of many species in the river, such as seagrass and fish.”

The Nature Conservancy, the University of Central Florida and a wide array of groups have worked to restore more than 20 acres of oyster reefs in Mosquito Lagoon thanks to a grant from NOAA. In November, the Loxahatchee River District, The Nature Conservancy and NOAA installed one of the first artificial reefs in the Loxahatchee River with the help of local volunteers.

On Thursday, half a dozen scientists waded waist-deep in the northwest fork of the Loxahatchee River to install hundreds of light sensors. The sensors sit atop a thin PVC pipe that scientists pound into the bottom on and around the oyster reefs. The light sensors are programmed to measure and record light levels every 5 seconds, providing a record of the reef’s impacts over several days and tidal cycles.

“What we hope this will confirm is that restored oyster reefs and other shellfish beds have a measurable effect on light levels in the surrounding waters,” said Anne Birch, coastal restoration director for The Nature Conservancy in Florida. “We want to provide additional evidence that oysters are more than simply a tasty hors d’oeuvre – that if reefs are restored they can provide function that is essential to both the economy and ecology of coastal areas.”

To learn more about shellfish conservation, visit nature.org/shellfish.

The Nature Conservancy is a leading conservation organization working around the world to protect ecologically important lands and waters for nature and people. The Conservancy and its more than 1 million members have protected nearly 120 million acres worldwide. Visit The Nature Conservancy on the Web at www.nature.org.