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Swarms of mayflies on wing over Lake Erie

Monday, July 26, 1999

By Don Hopey, Post-Gazette Staff Writer

They first appeared in early July on WJET-TV's Doppler radar weather screen as blue and green splotches of light, three miles out over Lake Erie, and closing on the Presque Isle beaches. If they had been incoming ICBMs, Edwin C. Masteller couldn't have been more excited.

 
  Edwin Masteller, professor emeritus of biology at Penn State Erie. Mayflies "are what I call a nice nuisance." (John Beale, Post-Gazette)

They were instead identified as hundreds of thousands, perhaps millions, of "Canadian sailors" -- local slang for the wispy, tall-winged mayflies, each about an inch and a half long, that haven't been seen in those numbers around Erie for more than 40 years.

"This has been a tremendous year for the mayflies. They are exotic, legendary, thrilling and suspenseful." said Masteller, 64, professor emeritus of biology at Penn State Erie, the Behrend College, whose ebullience about the bugs belies his retirement five years ago.

But it's not just about the bugs, which move in great clouds -- some 10 miles long -- from the lake to the shore where they cover buildings, sidewalks and roads.

It's also about the lake. The three species of mayflies -- ephemera simulans, hexagenia rigida and hexagenia limbata -- are North America's largest and thrive only in clean water. This year's swarms mean something good is happening out in the big lake, which was all but declared dead in the late 1950s, the victim of industrial pollution, untreated sewage and phosphate detergents.

"They're what I call a nice nuisance," said Masteller, who has collected and counted thousands of insects for the state's Mayfly Watch Program. "Although they can land in undesirable places -- in the 1940s they had to use snow shovels to remove the mayflies from sidewalks -- they mean the lake has become clean and inhabitable."



The snowstorms of mayflies along Pennsylvania's Lake Erie shore, so common in the first half of this century, ended in the early 1950s when massive amounts of organic pollutants discharged into the lake contaminated the bottom sediment and caused excessive algae growth.

When the algae died and decayed, a sediment layer formed that contained no oxygen and could not support the mayflies, which hatch from eggs in the sediment.

Pollution limits contained in the 1972 International Water Quality Agreement between the United States and Canada paved the way for the mayfly's return to the lake, said Eric Obert, associate director of Pennsylvania Sea Grant, a year-and-a-half-old outreach and environmental education program at Penn State Behrend.

"The mayfly is a water quality indicator, and we're excited by its comeback because of what it says about the lake and sediment," said Obert, whose organization hired the U.S. Geological Survey to do dredging in shallow Presque Isle Bay for the nymphs and their burrows.

None were found, Obert said, but the search will continue in deeper water.

The insects hatch in the lake sediment, where they then spend up to two years before swimming to the surface and flying to shore. On land or some other hard surface, they molt, then mate in the air before the females fly back over water to deposit as many as 8,000 eggs and die. The eggs sink into the sediment at the lake bottom.

The whole process, from the time the mayfly nymph swims to the surface of the lake and the eggs are deposited, takes only 72 hours.

The hatches occur sporadically from June through September, though the heaviest times are the last week of June and the first half of July.

The mayfly's resurgence was first noticed in the shallower western basin of the lake along the Ohio shoreline in 1994.

They have become so plentiful that they have caused power outages in Sandusky and Cedar Point, and signs warn motorists that roads can get slippery when wet with so many of the squashed insects.

The mayfly's reappearance along the Pennsylvania, New York and Ontario lake shores has been more recent.

Although growing in number, they haven't yet caused the problems seen in Ohio.

Masteller said that after a strong hatch in 1997, 1998 was a down year. This year the mayflies have alighted along the Pennsylvania shore in record numbers -- at least four times more numerous than two years ago.

"It's just been fantastic to see them come back in such numbers on the eastern end of the lake," he said. "We didn't think it could occur in the deeper water, but they're here."

Masteller said they may have had an assist from an unlikely and exotic benefactor -- the zebra mussel.

The aggressive, rapidly multiplying, alien bivalve hitchhiked from southern Russia's Black and Caspian seas to the Great Lakes in ocean-going ships' ballast in the late 1980s.

They are roundly considered the scourge of the Great Lakes and nearby waterways because they clog power and water plant intakes and crowd out native species.

But Masteller said the black and white stripped mollusks, which filter large amounts of water as they feed on minuscule plankton and impurities, have also cleared the lake, allowing sunlight to reach deeper depths.

"It's ironic, but the zebra mussels are cleaning up the water so that we now have oxygen in the lower reaches of the lake," he said. "They may be eliminating some clams and freshwater mussels, but I believe there is a strong correlation between their arrival and the mayfly's resurgence three or four miles out in the lake.

"Off Cleveland, the mayfly nymphs have been found in sediment at 48-foot depths, and I think they're even deeper here, off Erie."



Masteller talks about the television station's Doppler radar as though it is a crystal ball, showing the lake's future and echoes of its past.

"It's exciting to watch them show up on the radar screen and amazing to watch them move on time lapse," he said.

"As a practical measure, if we can locate where they emerge in the lake, we'll be able to tell people that it might not be a good night to travel near the shore because their windshields will be splattered or the roads will be slippery."

Doppler radar is different from conventional radar because it can detect and show an object in motion and the speed of that motion. It has been used to track the flight of flocks of birds and bats, but only a handful of researchers have used it to track insects.

The U.S. Department of Agriculture's Research Service uses it in Texas to track corn earworm and bollworm moths that cause millions of dollars of damage to corn and cotton crops in the south.

Meteorologist Tom Atkins, who works the evening shift at WJET, Erie's ABC affiliate, said he was surprised when the mayflies first showed up on his radar screen.

"We got the new Doppler in March and we were used to dealing with storms on the lake, but to see the mayflies was really exciting," he said.

"They'd show up like precipitation bands. The echoes would start about 9:30 at night and continue for about an hour, appearing as colorized clouds moving toward shore."

On nights when the hatches have been heaviest, the television station has shown their movement on the radar as part of its weather report on the 11 p.m. newscast.

Atkins said Masteller has been at the television station almost every night this month to monitor the radar and track the insects' flight path. Once he determines where they will be coming ashore, Masteller and volunteers from the Sea Grant and the college hurry to the lakefront to collect and count the bugs, which land thick on buildings, homes, trees, sidewalks, roads, even the historic brig Niagara, docked in Erie and commemorated on special Pennsylvania license plates.

During the heaviest hatches, Masteller has collected more than 950 mayflies under a netted hula hoop thrown on the ground.

"It's a neat thing for Erie," Atkins said.

"When my wife was a kid, she'd go down to the docks, lots of people would, to watch the clouds of Canadian sailors come in. It's neat to see them again."



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