Off pristine shores, mystery amid muck

Seaweed: Usually fueled by pollutants, a strange form of algae is surging across the clean waters along Assateague Island.

March 22, 2002|By Heather Dewar | Heather Dewar,SUN STAFF

CHINCOTEAGUE BAY - The first sign of spring here lies under the sea, and it isn't a joy to behold.

Imagine the most tangled spool of fishing line you've ever seen. Multiply it till it's 3 feet wide and 10 feet long, and color it a lurid green. This is chaetomorpha, a form of underwater plant life that is growing fast in the shallow waters along Assateague Island National Seashore.

Until two years ago, fishermen had seen only a few tiny patches of the stuff in these waters, which were once believed to be some of the most pristine in the state. But when scientists began looking for it last year, they found it almost everywhere in eastern Sinepuxent and Chincoteague bays.

Some scientists think the floating aquatic weeds are the reason sea grasses have died in one of the most lush underwater meadows left in Maryland. And the tangled, fibrous algae are a boater's bane.

"If it gets hung up in your prop, it'll stall your motor out, and you've got to take a knife and cut it off," said Calvin Jordan, a biologist for the Maryland Department of Natural Resources.

The stringy stuff is one of several seaweed varieties, known to scientists as macroalgae, that have recently come to dominate parts of Maryland's coastal bays.

"It was the spring of 2000 when all hell broke loose with macroalgae," said David Wilson of the Maryland Coastal Bays Program. "The stuff was so thick that some people literally could not get their boats out of their canals."

The reason for the seaweed's sudden abundance is a mystery. The coastal bays haven't been as well studied as the Chesapeake, and scientists don't have enough information to pinpoint a cause.

The thick mats are a nuisance, clogging fishermen's nets and stinking as they die and wash ashore. In some places, they imperil other aquatic life by robbing the water of precious oxygen. In other spots, they may help young sea creatures survive, providing hiding places from predators for shrimp, fish and crabs.

As habitat for sea creatures, "it's better than nothing," said David Goshorn, chief of DNR's living-resource assessment program, but not as good as the underwater grasses it may jeopardize.

To find out how extensive the seaweed is, DNR biologists have completed the first comprehensive survey, sampling 600 locations once a season for a year. They found a mix of seaweed varieties in the bays' most polluted waters - and in some of the purest.

The same phenomenon is being observed around the world in both fresh and salt water, including Norwegian fjords and Pacific Northwest lakes. "Globally, this stuff has been appearing in a lot of coastal areas and causing problems," said Margaret McGinty, a DNR biologist who supervised the survey.

On a rainy March morning, McGinty and co-worker Al Wesche hauled a custom-designed dredge - steel bars and metal mesh, with a net sewn into the bottom - through murky waters near the Ocean Pines development. Within minutes, the two were smeared with muck and several kinds of seaweed.

"Ugh," said McGinty, as she hauled up a weed-draped anchor in Herring Creek, off Isle of Wight Bay. "This stuff is so thin and slimy, it's just a ball of goop."

McGinty squeezed the water from a reddish-brown bucketful. A tiny crab skittered out, and killifish wiggled amid the filaments. In spite of nutrient pollution from nearby houses and farms, the creek teems with life, Wesche said - blue crabs and shrimp, flounder and sea trout, mummichogs and other bait fish. But the dense algae makes it impossible to catch them.

The shallow waterways are tainted with runoff from septic tanks, parking lots, farm fields and poultry plants. The runoff acts as fertilizer, fueling algae growth.

It's no surprise to find the seaweed in the waters west of Ocean City, where levels of nutrients such as nitrogen and phosphorus are similar to those in some lower Eastern Shore rivers, Goshorn said. But the protected shallows of Chincoteague Bay are another matter.

Off Assateague Island in the late-winter mist, the DNR biologists' boats were the only signs of humanity. The water's soft gray-green, the color of weathered copper, blurred into the silver clouds. A blue-gray smudge of silhouetted pines marked the island's distant high ground, where wild ponies grazed amid marsh grass. When the biologists cut their engines, the hush was quickly filled by the loud cries of water birds - Canada geese, bufflehead ducks, and gulls.

DNR's Jordan dunked a plastic tube fitted with a clear bottom pane into the water, and a burst of brilliant spring green appeared. Growing on the bottom were new shoots of eelgrass - the mainstay of the underwater meadows that normally shelter fish and crabs.

Growing over, around and through the young grasses, like a tangled net, was the macroalgae.

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