Existing protocols not halting invasive species spread into Great Lakes

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Existing protocols not halting invasive species spread into Great Lakes

 

 

February 25, 2009

Jim Moodie / www.manitoulin.ca

 

 

CHICAGO-A recent report from the US Environmental Protection Agency (EPA) warns that the current regime in place to catch invasive species won't prevent dozens of new exotic pests from entering the Great Lakes.

 

The study, titled Predicting Future Introductions of Nonindigenous Species to the Great Lakes, identifies 30 non-native species that pose a medium or high risk of reaching the lakes and 28 others that have already gained a toehold and could proliferate more widely. They include such ominous-sounding critters as the monkey goby, the fishhook waterflea, and the doctor fish (technically called a tench fish).

 

These 58 newcomers would join the 185 invaders that are known to have already found a niche in the Great Lakes. Not all, it should be noted, are wreaking utter havoc: according to the EPA, only 13 of the existing intruders, such as the zebra mussel and sea lamprey, have done extensive harm to the aquatic environment and the regional economy.

 

Still, the report recommends prompt action to nip the ingress of more unwanted species, and points to a number of high-traffic ports as areas where tougher monitoring should be implemented. These include Duluth, Minnesota; Superior, Wisconsin; and Toledo, Ohio. Each is a site that receives a high concentration of discharged ballast water, a medium that accounts for over two-thirds of the invasive species that have entered the lakes.

 

Both Canada and the US now require ocean-going vessels to flush their ballast at sea, and have recently enacted requirements for ships to rinse empty tanks with saltwater in hopes of killing organisms that can lurk in residual pools at the bottom.

 

Still, even with such measures in place, "it is likely that nonindigenous species will continue to arrive in the Great Lakes," the report predicts, as some saltwater-tolerant species may survive ballast-water exchange and tank flushing. "Despite these ballast-water regulations, at least 13 new (invasive species) are believed to have entered the Great Lakes from ballast water since 1993," the report notes.

 

Hugh MacIsaac, a University of Windsor biologist and director of the Canadian Aquatic Invasive Species Network, believes the ballast regulations are quite effective, however, and that the picture painted by the EPA is unreasonably alarmist. Flushing and ballast-water exchange should kill 99 percent of organisms, he told the Associated Press, adding, "I would be very surprised if their prediction comes true."

 

Canada implemented voluntary ballast-water guidelines to stem the spread of invaders in 1990, with tougher rules introduced in 2006 that now require all ships entering Canada's waters to manage their ballast water.

 

The law, through the Canada Shipping Act, states that cargo ships must: exchange their ballast water in open ocean; treat their ballast water while in transit; discharge their ballast water to a reception facility; and retain their ballast water on board ship.

 

According to Environment Canada, a mid-ocean exchange of freshwater for seawater in a ship's ballast tanks will take care of most invaders, as the high salt content of the latter tends to kill off the freshwater organisms, while the number of salt-tolerant creatures are relatively few.

 

When this ballast is discharged at the port of destination, "the very small number of organisms that would be taken in from the high seas would not survive in the port's waters," the department states in an article at EnviroZine, its online newsmagazine.

 

However, there is growing evidence that this approach is far from foolproof, and a more effective way to stem the alien tide is to treat the ballast water during a ship's voyage with organism-zapping agents or by depriving these aquatic nasties of oxygen.

 

There are about 30 treatment systems being developed around the world, four of which are being tested in Canada. Two of the more promising methods that Environment Canada has been studying are The Peraclean Ocean treatment, which uses peracetic acid and hydrogen peroxide to eliminate aquatic hitchhikers; and Ballaclean, which employs deoxygenation technology to choke the life out of the little stowaways.

 

Neither is perfect: the former leaves toxic residues in the treated water that may take up to a week or more to dissipate; the latter requires a long period of time for the process to be effective, and can cause increases in ammonia and other byproducts that render the discharged water hazardous for the environment.

 

While ballast-water discharge is the most prevalent pathway for invaders, the EPA report notes that a high rate of this activity in one area of the basin does not necessarily translate to more species invasions. It points to the example of Lake Superior, which counts the most discharges of ballast water in the Great Lakes, yet has fewer invasive species than the other lakes.

 

"The low nonindigenous species colonization rate in Lake Superior may be due to any of several factors including cooler temperatures, a high ratio of deeper waters, low food availability due to low productivity, and low calcium concentrations," the report states.

 

The US environmental agency attributes 65 percent of invasive species in the Great Lakes to shipping and ballast water. The remainder come through a variety of conduits, including canals, bait transfers, fish farms and aquarium releases.

 

The study employs a type of ecological modelling, combined with remote sensing data, in order to predict which areas of the Great Lakes would become suitable habitats for the next round of invasive species.

 

Lake Huron, for instance, is considered an area of "high suitability" for the blueback herring, a medium-sized fish very similar to an alewife.

 

Indeed, most of the Great Lakes, save for the deeper parts of Lake Superior and all of Lake St. Clair, are considered a promising habitat for this newcomer.

 

By contrast, Lake Huron is an unlikely home for the rudd, whereas circumstances on Lakes Erie and Ontario are ripe to receive these hardy, thick-bodied fish. We're also, thankfully, a zone of "low suitability" for the roach, a member of the carp family. (Again, Erie and Ontario are most apt to host this type of invader.)

 

According to Jennifer Nalbone, invasive species director for the advocacy group Great Lakes United, the EPA report acts as a wake-up call for tougher legislation and monitoring. She told the Associated Press that it "reinforces the need for further measures to keep foreign species out, including requiring onboard technology to sterilize ballast tanks."