22 May 2009

Oyster reefs: most severely impacted marine habitat on the planet

85% of the world's oyster reefs have already been lost. Due mainly to poor fishing practices and coastal developments.
Killed oysters seen this month at Changi.

Oysters provide a number of key services within their ecosystems, such as filtering water, and provide food for other organisms, such as fish, crabs and birds. Oyster reefs may also protect shores from erosion and encourage the growth of seagrasses.

A recent report shows that oyster reefs were the most severely impacted marine habitats on the planet. The study, written by scientists based in five continents, found reefs that were "functionally extinct" in a number of regions, including North America, Europe and Australia.

Two main barriers impeding oyster recovery efforts were a lack of awareness that shellfish habitats were in trouble, and the assumption that non-native shellfish can be introduced in areas where native species are declining.

Habitat loss 'hitting shellfish'
BBC News 21 May 09;
Marine habitat loss is causing a decline in shellfish populations, which is having an adverse knock-on effect on sensitive ecosystems, a study suggests.

Described as the first global assessment of its kind, it warns that 85% of the world's oyster reefs have already been lost.

The findings, published by The Nature Conservancy (TNC), adds that many other reefs are now "functionally extinct".

It blames poor fishing practices and coastal developments for the declines.

Lead author Mike Beck said the report showed that oyster reefs were the most severely impacted marine habitats on the planet.

"We're seeing an unprecedented and alarming decline in the condition of oyster reefs, a critically important habitat in the world's bays and estuaries," he said.

Shell shocked

The study, written by scientists based in five continents, found reefs that were "functionally extinct" in a number of regions, including North America, Europe and Australia.

"However, realistic and cost effective solutions within conservation and coastal restoration programmes, along with policy and reef management programmes provide hope for the survival of shellfish," Dr Beck added.

Oysters provide a number of key services within their ecosystems, such as filtering water, and provide food for other organisms, such as fish, crabs and birds.

The assessment identified a number of "driving forces" behind the reefs' decline, including "destructive fishing practices, coastal overdevelopment, poorly managed agriculture and poor water quality".

Although these problems have been around for decades, the report said there were two main barriers that were impeding oyster recovery efforts.

The first was a lack of awareness that shellfish habitats were in trouble, and the second was an assumption that non-native shellfish can be introduced in areas where native species are declining.

"We want to raise awareness that the world's remnant oyster reefs and populations are important, since they represent some of the last examples of reef habitats produced by a particular species of oyster," explained co-author Dr Christine Crawford, from the University of Tasmania.

"We have an opportunity to conserve such reefs in Australia and elsewhere with the results of this assessment," she added.

Among the report's recommendations were to elevate native, wild oysters as a priority species for conservation, and ensuring existing protection policies were extended to include the vulnerable reefs.

UCF Biologist Restores Oyster Reefs During Global Shellfish Demise
Christine Dellert, University of Central Florida 21 May 09
Relying on mesh, drilled-out oyster shells and zip ties, Linda Walters’ work has added about 315,000 oysters to protected waters in Canaveral National Seashore during the last two years.

The University of Central Florida biologist’s unique solution is succeeding at a time of global shellfish demise. A report released today from The Nature Conservancy shows that about 85 percent of the world’s oyster reefs have been lost, making these reefs the “most severely impacted marine habitat on the planet.”

“Oysters are a cornerstone species,” said Walters, who partners with The Nature Conservancy on the local restoration project. “They create a complex, three-dimension topography to an otherwise barren muddy or sandy bottom.”

Walters and her students have discovered nearly 150 other species that use the oyster reefs for shelter or food in Canaveral National Seashore. These important shellfish also purify the lagoon as they filter water for their food.

Alongside her husband, Paul Sacks, Walters has helped restore about 19 acres of oyster reefs in Mosquito Lagoon, the northernmost region of the Indian River Lagoon system in one of the most biologically diverse estuaries in North America.

Walters’ research found that boat wakes are causing reef destruction here, sending oysters tumbling from the lagoon bottom to tall piles of sun-baked, barren shells above the high-tide line. In 2000, about 15 percent of the reefs in Canaveral National Seashore were impacted. Walters says that number is much greater today.

To survive, oysters need to attach themselves to other oyster shells and spend time feeding underwater, Walters said. Since 2007, she and more than 10,000 community volunteers have made and deployed the underwater mesh and weighted “oyster mats,” creating safe, stable homes for the shellfish to thrive.

Each mat has about 36 shells attached when it’s first placed in the water. Within 18 months, the number of live oysters on restored reefs equals the number of oysters on reefs in areas not impacted by boat wakes.

Signs installed around the reefs alert boaters to the protected area. Since the restoration efforts started, Walters has documented the reemergence of sea grass near oyster reefs in areas of the estuary where it hadn’t been for decades. She and her colleagues are also exploring how effective the oyster mats are at preventing shoreline erosion.

“From all accounts, this project has been extremely successful,” said Anne Birch, The Nature Conservancy’s director for the Indian River Lagoon system. “There aren’t many marine-related projects that offer the public such a hands-on opportunity.”

Many organizations fund the project, including a National Partnership grant between the National Oceanic and Atmospheric Administration Restoration Center and The Nature Conservancy. Walters and Birch say community involvement also has been key to its success.

Walters jokingly refers to the mat making as “oyster arts and crafts,” and everyone from Eagle Scouts and university students to local businesspeople and retirees have chipped in to make more than 11,000 mats. Many local middle and high school teachers, including Walters’ past students, also enlist help from their classes. As a bonus, volunteers get to name the restored reefs.

“We’re trying to reach everyone, young and old, to teach them how to be better stewards of the environment,” Walters said.

To connect with an even younger, preschool-aged audience, an illustrated children’s book about the oyster project will released as early as next week. Entitled “An Afternoon in Mosquito Lagoon,” the book was produced by Walters and Birch and written by Suzie Caffery and Diahn Escue from UCF’s Creative School for Children.

The book will be distributed for free to local schools and given to some of the project volunteers.

Mat-making volunteer and deployment opportunities will continue through August. Walters and Birch are hopeful that additional funding will become available to continue restoration of more than 50 additional dead reefs in Mosquito Lagoon.

To see The Nature Conservancy’s report, go to http://www.nature.org/shellfish.

And watch a short video clip featuring Walters' work here.

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