A nettle-some problem on Potomac

By FRANK DELANO

An overabundance of jellyfish in the Chesapeake Bay is causing problems for power plants in Maryland.

According to reports filed with the U.S. Nuclear Regulatory Commission, jellyfish have clogged intake pumps three times this month at the Calvert Cliffs Nuclear Power Plant in Calvert County, Md.

On July 7, an influx of jellyfish in a pump that circulates cooling water forced the plant to reduce the power output of its Unit 1 to 41 percent of capacity. The unit returned to 100 percent production after engineers cleared and restarted the pump, the NRC report said.

Masses of jellyfish also jammed water pumps July 6 and as recently as Wednesday, but the plant's two units maintained 100 percent output, the reports said.

Jellyfish are also causing headaches at Maryland's largest power plant, the Chalk Point Generating Station on the Patuxent River in Prince George's County, an environmental analyst said.

Pat Langley said jellyfish have clogged large nets protecting cooling-water intakes. A local waterman is now dumping jellyfish from the outermost line of the nets twice a week, he said.

"It's not a perfect system, but it seems to be doing a good job," Langley said.

Chalk Point is about 30 miles upstream from the mouth of the Patuxent River. From there, Calvert Cliffs is about 10 miles up the bay.

There are indications that the annual infestation of jellyfish in Chesapeake Bay waters is worse this year than in prior years.

Langley said he could remember no other jelly-fish seasons where barrier nets had to be cleared as often as this year.

An online search of NRC event reports dating back to 1999 revealed no jellyfish problems at Calvert Cliffs prior to this month.

Jellyfish are also abundant in the lower Potomac River, but less so in fresher waters upstream.

That is good news for river swimmers at Colonial Beach, about 50 miles up from the mouth of the Potomac.

"Aside from a couple of little ones, we've had no problems with them. They usually don't show up here until around Aug. 1," said Colonial Beach Mayor G.W. "Pete" Bone Jr.

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Neither jelly nor fish

A jellyfish is not really a fish. Related to sea anemones and corals, they have no fins or muscles and are at the mercy of the wind and the tides. They use a weak, pulsating swimming action for locomotion.

During the summer, there are typically three types in bay waters, researchers say: moon jellies, a relatively harmless variety that can reach the size of a dinner plate; nonstinging oval comb jellies; and the nettle, which can grow to 18 inches across with tentacles several feet long.

Nettles come in an array of hues and sizes and are the stinging variety responsible for the painful close encounters with bathers.

The sting, painful but rarely serious, is caused by tiny barbs on the tentacles that shoot out on contact with an object--such as a swimmer's arm--and inject a poison.

Date published: 7/15/2006

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