Bay Daily: Oysters Can Help Clean the Bay, Can't Fix the Bay

07/20/2012

Oysters Can Help Clean the Bay, Can't Fix the Bay

One of the keys to restoring the Chesapeake Bay to good health is restoring the Bay’s native oyster population to good health.

Why? Beyond being one of the Bay’s most iconic cultural and economic critters, oysters are what’s called a keystone species, an animal critical to a balanced, properly functioning ecosystem. Oysters naturally clump together to create reefs beneath the water’s surface, over time forming large mounds of gnarly shells that provide food and shelter for an array of other Bay creatures. Ask anglers where the best fishing in the Bay is and likely they’ll point to an oyster “rock” or reef area.

And just by eating and respiring, oysters help filter and clear Bay waters, removing algae and sediments that cloud the water and cause big Bay problems. One adult oyster can clear about 50 gallons of water a day. Scientists estimate that in pre-Colonial times, there were enough oysters in the Bay to filter the entire quantity of water in the Chesapeake in just a few days.

Since then, of course, oyster numbers have declined dramatically because of over-harvesting, pollution, and disease. Today, the Bay’s oyster population is but a tiny fraction of its historic levels. That’s a huge loss for human gourmands, the plants and animals that depend upon oysters, and for the Bay’s water quality.

As important as oysters are to the Bay, they are not a silver bullet for restoring it. They may have once cleared the Bay of algae and silt, but that was in an era of a balanced, near pristine Bay ecosystem. Today’s Bay watershed is very different, overloaded with millions of pounds of excess nitrogen, phosphorus, and sediment from man’s activities on the land.

Even if oysters are restored in large numbers, today's flood of pollution would overwhelm them, a recent study by Auburn University and the Dauphin Island Sea Lab concluded.

“In the water bodies that are the most polluted, there's just not space available,” Dauphin Island Sea Lab scientist Ruth Carmichael said in a published report. “In the most polluted urban estuaries, you just don't have enough room for the oysters. You would have to blanket the bottom of the entire estuary in oysters.”

Restoring the Chesapeake Bay will require many efforts, including restoring oysters, but Job One remains dramatically reducing manmade pollution from multiple sources. That’s why the federal-state Bay cleanup blueprint targets big cuts in pollution from wastewater treatment plants, runoff from farms and cities, and industry pipes and smokestacks.

Meanwhile, the challenge to restore native oysters is difficult and complex, a trial-and-error process of incremental gains and setbacks. Just as it took many decades to decimate the Bay’s oysters, so too may it take decades to bring the population back. Success will likely come one creek, one cove, and one river at a time, over many years and replicated across the Bay region.

One effort in one river was in the news this week. The Chesapeake Bay Foundation (CBF) and the Elizabeth River Project (ERP) joined forces to restore a half-acre oyster reef in Norfolk’s Lafayette River. The partnership first laid down a base of concrete rubble, then coated it with oyster shells, then topped the area with baby oysters grown by CBF and local volunteers.

This week, CBF began surrounding the reef with the first of 400 reef balls, concrete spheres full of nooks and crannies and coated with baby oysters. The goal is to restore a healthy oyster population to the Lafayette, part of a larger effort to restore the river to fishable-swimmable standards by 2014. And that’s part of the larger Bay cleanup blueprint aimed at restoring the Bay by 2025.

More oysters and less pollution, one creek, one cove, one river at a time.

Chuck Epes
Chesapeake Bay Foundation

Posted on 07/20/2012 at 03:16 PM | Permalink

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Bay Daily

07/20/2012

Oysters Can Help Clean the Bay, Can't Fix the Bay

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