Keeping Aquatic Invaders Out: Pathways and Roadblocks

The St. Lawrence Seaway was a major route for invasive species to enter the Great Lakes before a 2006 change in ballast water regulations. Credit: Kunal Mukherjee

Quagga mussels. Hemimysis. Alewives. Sea lamprey. Phragmites. These are just a few of the more than 180 non-native species that have entered the Great Lakes basin over the past few centuries. They’ve come through canals, from ships, and escaped from gardens and other private lands. Managing existing populations of these creatures is difficult enough, but how are officials keeping new invaders out? It all depends on the species, the likeliest route for that species and how people could inadvertently transport them into the basin.

The single biggest pathway invasive species had in the past was hitching a lift inside the water-filled ballast tanks of ships crossing the ocean, according to Jeff Brinsmead, senior invasive species biologist with Ontario Ministry of Natural Resources and Forestry. Ballast water is necessary for maintaining a ship’s balance when cargo and fuel usage change its mass. For decades, ships could simply take on ballast water --- with its sediments --- in their home port and dump it when they arrived in the Great Lakes – inadvertently dropping dozens of species in a new ecosystem. The US Environmental Protection Agency estimates about 30 percent of all invasive species in the Great Lakes arrived through ballast water. Not all non-native species are considered invasive; invasive species are a subset of that group whose introduction causes – or is likely to cause – economic or environmental harm, or harm human health. A sea lamprey attached to a salmon caught in northern Lake Huron. Credit: M. Gaden/Great Lakes Fishery Commission

Transoceanic Invaders and the St. Lawrence Seaway

Some species introductions date back almost 200 years, like the parasitic sea lamprey who gained access to the upper lakes with the opening of the Welland Canal, bypassing Niagara Falls.  But it was the opening of the St. Lawrence Seaway in 1959 that sparked a dramatic increase in the Great Lakes, Brinsmead said. Ballast water and invasive species was likely not something anybody involved with the seaway had thought about or considered when it was opened, and it took until 2006 for the United States and Canada to realize the extent of the problem and address it, he said. That year, the St. Lawrence Seaway Corp. and Canadian government agreed to new regulations requiring ballast water to be exchanged in the open ocean before vessels enter the seaway, in line with proposed regulations by the International Maritime Organization and its International Convention for the Control and Management of Ships’ Ballast Water and Sediments. The EPA implemented similar measures that took effect on Jan. 1, 2016. Since 2006, only one new species has been confirmed in the Great Lakes, Brinsmead said: a tiny crustacean known as a copepod that may have already been in the Great Lakes prior to 2006 and went unnoticed. Researchers believe ballast water is how invasive species like zebra mussels, quagga mussels and Hemimysis – also called the “bloody-red shrimp” – entered the Great Lakes.

Moving Within the Basin as Hitchhikers

But while that may have slowed down new species from entering the Great Lakes, species already in the waterways still can inadvertently be moved to inland lakes or other parts of the Great Lakes. These pathways don’t require major shipping. A watercraft --- be it a boat, kayak or Jet Ski, for example --- moved from one body of water to another without amply being cleaned, drained and dried can bring tiny invasive passengers into a different body of water. That includes microscopic mussel larvae to invasive plant seeds. Anglers using nonnative bait can introduce those species into a new environment, whether by dumping them into the water system or through escapees. And people with home aquariums or gardens with nonnative plants and animals can accidentally allow them to spread.

Invasive Phragmites weeds, like these on the shore of Lake Huron in Lexington, Michigan, settle in wetlands and coastal areas, where they can quickly choke out native plants and ruin habitat for aquatic and terrestrial creatures. Credit: Sara Hattie

To combat these pathways, Ontario and the Canadian government use a combination of educational outreach and regulations, including the Ontario Invasive Species Act, which came into force in November 2016. Under that act, 16 species including round goby, Asian carp and northern snakehead are prohibited from being brought into the province, while plants like Phragmites or Japanese knotweed are restricted – people with those plants on their property won’t be penalized, but they can’t be bought, sold or traded. Brinsmead said Canada encourages people to use native and non-invasive plants for their gardens as replacements.

In the United States, the US Fish and Wildlife Service (USFWS) uses several national laws and executive orders to manage invasive species, alongside state-level regulations and activities. Much like Ontario, US officials recommend cleaning, draining and drying boats traveling to different water bodies. Under the Lacey Act, USFWS also can determine the risk factors of bringing specific nonnative species in commercially to convince the animal trade industry to refrain from bringing in specific species; they can also prohibit species entirely from crossing national or state lines.

Asian Carp and Electrical Barriers

Asian carp remain a major concern for Canadian and US officials. In addition to monitoring the lakes for their presence through “environmental DNA” and netting trawls, US agencies are trying to improve ways to keep them from getting into Lake Michigan via the Mississippi River. Currently the river is separated from the lake with three electrical barriers in the Chicago Area Waterway System, which maintain electric fields in the water to drive fish away.

Research is also underway on other methods to discourage carp from entering Lake Michigan through that pathway. The carp are about 45 miles (72 kilometers) away from Lake Michigan behind both the electric barriers and three lock and dam barriers. But officials throughout the basin are taking the threat seriously following a 2012 Illinois-based federal district court ruling that the canal should not be permanently closed, a ruling later upheld in an appeals court. There have been tests suggesting the barriers lose some of their potency when ships are moving through them toward the Mississippi River, so fine-tuning the system continues.

The Asian Carp Regional Coordinating Committee released its 2017 Action Plan in January, with a list of proposals including a new electric barrier in the Chicago canal, additional monitoring and continued development of new control measures.

Given the costs of managing invasive species and the damage they can do to their newfound ecosystems, keeping new ones out is an important job for everyone, from individuals and communities to businesses and governments.

Researchers from the US National Oceanic and Atmospheric Administration pull invasive quagga mussels out of Lake Ontario during a trawl. Credit: NOAA