Watch list predicts Great Lakes’ future nonnatives

As many agencies try to rid the Great Lakes of foreign plants and animals causing ecological havoc, a team from the National Oceanic and Atmospheric Administration recently identified the region’s “future” invaders.

Staff compiled a “watch list” of 52 nonnative crustaceans, fish, plants and invertebrates. Perhaps to no one’s surprise, two species of Asian carp—bighead and silver—topped the list. Five Great Lakes states continue a court battle to close Chicago Sanitary and Ship Canal locks to stem the carp’s advance.

“Clearly the ones that would be of greatest concern are the two Asian carp species simply because we haven’t closed off the canal,” said Hugh MacIsaac, invasive species chair of the Department of Fisheries and Oceans at the University of Windsor  and one of several experts asked to review the list.

Aquatic plants like water lettuce (shown here) and water hyacinth topped a list of potential Great Lakes aquatic invaders. Photo: Nicole Marti via Flickr.

The effort also identified potentially troublesome plants like the water lettuce and water hyacinth introduced through aquarium and pond shops.

The list is part of the Great Lakes Nonindigenous Species Information System, a database of Great Lakes aquatic non-native species that helps lake and resource managers decide how to best manage aquatic invaders.

Researchers listed foreign species that might establish in the Great Lakes and spread. The potential troublemakers were identified after reviewing scientific studies published between 1998 and 2010. Species were also listed if they could survive and be transported into the Great Lakes, could reproduce there and could be introduced multiple times.

The list is a first step toward the Great Lakes Restoration Initiative’s goals of early detection and rapid response of invasive species, said Rochelle Sturtevant, a principal investigator on the study and Great Lakes Regional Sea Grant Extension educator. That initiative addresses pollution, invasive species and habitat restoration through funding to local, state and federal governments, universities and non-profit organizations.

Sturtevant said species could be added to the list if climate change makes once uninhabitable environments habitable. Others may be removed as researchers assess whether recent regulations have made it harder for species to be transported in the ballast water of ships.

Impacts to the list based on climate change were hard to address, Sturtevant said.

Studies considered whether a species could survive a Great Lakes winter.

“Most of those studies did not take climate change into account when making that determination,” Sturtevant said. “There just isn’t enough data yet on what climate change is realistically going to do to the region…much less on an individual species by species basis of whether it’s going to overwinter. The data’s just not there.”

John Magnuson, a zoology and limnology professor emeritus at the University of Wisconsin-Madison has studied climate change impacts to lakes, rivers and freshwater fish.

“The warm water fishes that do really well in the warmest waters of our shorelines in the Great Lakes are also able to withstand winter temperatures at a couple degrees Centigrade,” Magnuson said.

That’s about 36 degrees Fahrenheit.

Warm water fishes include carp, bluegill and crappie. Magnuson said fish species with similar “thermal biology” might be more likely to establish with warming water temperatures.

Climate change may create favorable habitat for other unlisted species like limnoperna fortunei, the Golden Mussel, according to Alexander Karatayev, director of Buffalo State University’s Great Lakes Center for Environmental Research and Education who has studied the mussel.

“This species is adapted to higher temperatures than zebra mussel, therefore climate change…may further the spread of the species,” he said.

The Golden Mussel can withstand a variety of environmental conditions. Photo: Alexander Karatayev.

Though the Great Lakes are too cold right now, Karatayev said increasing water temperature may allow the mussel to survive. It can adapt to a variety of environmental conditions including low pH, high salinity and low oxygen. Though it prefers warmer water, it can also withstand cooler temperatures.

South American researchers hypothesize that the southeast Asia native was introduced there via ballast water in the early 1990s. It quickly spread within five to six years, according to Karatayev. The mussel is a powerful water filter like the zebra mussel and poses problems by clogging water intake valves for industrial and power plants, water treatment stations and refineries.

“It’s very likely that in the near future it can get to North America because now it’s almost everywhere in South America,” Karatayev said.

Most species listed also have a “high probability of invasion if introduced to the Great Lakes via residual ballast water” or sediment according to list notes. Ballast water has long been recognized as a pathway for aquatic invasive species. Since 1959, introduction through ballast water is the most likely source of a majority of introductions, according to a National Oceanic and Atmospheric Administration report.

“A lot of these studies date to the early 90s when ballast water regulations were still being discussed and were just brought into play,” Sturtevant said.

That means some species may come off the list once recent regulations are considered, and some species are already listed with a reduced chance of entering due to 1993 ballast water regulations. Those regulations require ships to flush ballast tanks with seawater, providing a more hostile environment for potential nonnative species.

“I think ships pose a much lower risk today than even 100 years ago,” said MacIsaac, who is also director of the Canadian Aquatic Invasive Species Network.

Sturtevant said nonnative species were put on the list even if studies suggesting they could establish in the Great Lakes were conducted during ballast pre-regulatory years. Impact assessments conducted for fact sheets on each species will help with decisions to remove, add or rank species on the list. The sheets will be released sometime this year.

Species decisions were reviewed by experts from U.S. and Canadian universities and governments.

The project was funded by a small portion of $250,000 the agency received in 2010 Great Lakes Restoration Initiative funds and support from the Great Lakes Environmental Research Laboratory.