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.

Across the Potomac in Charles County, Md., environmental analyst Liz Spitzer said jellyfish have caused no problems at the Morgantown Power Plant on the Maryland side of the U.S. 301 Bridge.

Marine scientist David A. Nemazie of the Center for Environmental Science of the University of Maryland, said jellyfish are a "balloon species" whose populations can explode under optimum conditions of salinity and water temperature.

Ideal conditions for jellyfish often occur in summer in the mid-Chesapeake Bay, including saltier portions of the Patuxent, Potomac and Rappahannock rivers, Nemazie said.

He said jellyfish populations seem to be increasing along with increases of nutrients such as nitrogen and phosphorous in the waters where jellyfish are found.

"Large, worldwide blooms of jellyfish are regular occurrences now. They used to be rare before," Nemazie said.

A Web site maintained by the National Oceanic and Atmospheric maps the probability of jellyfish in the Chesapeake Bay. Its address is http://coastwatch.noaa.gov/seanettles

Jellyfish are not the only marine species recently to beset the Calvert Cliffs power plant.

The plant reported Tuesday to the NRC that 150 to 200 cow-nosed rays had died on trash racks protecting water intakes of both units.

"The apparent cause was low oxygen levels in the Bay water," the report said. Power output was not disrupted by the death of the stingrays.

Staff reporter Rusty Dennen contributed to this story.

http://fredericksburg.com/News/FLS/2006/072006/07152006/206385

To reach FRANK DELANO:804/333-3834 Email: fpdelano@gmail.com