The Invasion Continues Another exotic algae is having an impact on Pennsylvania waters

The Associated Press

MINNEAPOLIS — An aquatic weed is creeping across the Great Lakes region. It grows really fast and is very hard to kill.

Scientists don’t know a lot yet about starry stonewort, but they’re hurrying to find out more. The robust algae first turned up in North America in 1978 in the St. Lawrence River in New York. Researchers think it probably arrived in ballast water from ships entering the Great Lakes.

It wasn’t a big concern for about 30 years, but then it took off. Now it’s widespread in Lake Erie waters of western New York, Ohio and Pennsylvania, where it has been sighted on the lagoons and canals of Presque Isle.

The algae has reached beyond the Great Lakes. On Michigan’s Lower Peninsula it has infested more than 200 inland lakes. It is present in inland waters of Canada, Vermont and Indiana. In Pennsylvania it has been documented in Lake Arthur, Butler County.

The name starry stonewort comes from the tiny, white six-pointed starshaped bulbs, or bulbils, that grow on the stems. In its native Europe and Asia it is endangered and even considered beneficial, but it turned aggressive in American waters.

Starry stonewort is difficult to kill with herbicides because it doesn’t have a vascular system that could carry the poison to the entire plant, said University of Minnesota invasive species specialist Dan Larkin. Herbicide treatments often result in a “haircut effect” that burns off the top but leaves the rest alive to regrow.

The weed mats — up to 7 feet thick and spreading across the bottom — can be a nuisance to boaters and anglers. Scientists are concerned about the potential harm to native plants, fish habitats and other disruptions to aquatic ecosystems. But last year Larkin said there was almost no peer-reviewed research documenting the algae’s adverse effects. Still, experts wouldn’t be sounding the alarm if they weren’t worried.

Researchers are just starting to understand the conditions in which the algae thrives, and modeling suggests that large swaths of the United States could be highly suitable, including the mid-Atlantic states, the Great Plains and much of the West, Larkin said,

Starry stonewort reproduces when fragments and bulbils break off, and they can hitchhike on contaminated boats and trailers. Recent discoveries have often been concentrated near public accesses such as boat ramps. Scientists don’t know yet how long those plant fragments can stay viable out of water, Larkin said.

The algae is sometimes misidentified because the distinctive bulbils don’t appear until late in the season. In 2016 it was confirmed in a lake in northern Minnesota, but the infestation probably went unnoticed for several years. That finding is concerning because the Mississippi River flows through the lake, a popular fishing destination. No infestations have been found downstream so far, though monitoring continues, said Tim Plude, an invasive species specialist with the Minnesota Department of Natural Resources. He said the species doesn’t seem to like fastmoving water.

But it’s tough. Wisconsin has had some success with THIS WEEK: To slow the spread of invasive aquatic species, should Pennsylvania law require boaters to clean hulls and trailers at launching ramps? • Yes • No • LAST WEEK: Many Pittsburgh anglers have never fished for hybrid striped bass despite their size and fighting reputation. Have you targeted hybrid striped bass? an expensive method known as DASH — Diver Assisted Suction Harvesting. Divers hand-pull plants and feed them into a big suction hose.

Different approaches were attempted on a popular recreational lake in central Minnesota where the weed was first discovered in the state. Crews used a mechanical harvester, aided by a diver, and followed up with herbicide. Researchers hopes to learn whether other methods of starry stonewort eradication work.

The best strategy, they say, is prevention. Boaters are urged to thoroughly clean their watercraft, trailers and other equipment of plants, mud and other debris before moving them from one body of water to another.