Ballast Water Management in the Great Lakes Reduces the Introduction of Aquatic Invasive Species: Fisheries and Oceans Canada Study
The first scientific study of the Great Lakes Ballast Water Program reveals that the strategy is very effective at protecting waterways from the introduction of new aquatic invasive species, which can have devastating effects on natural ecosystems. Since the introduction of the current regulations in 2006, no new invasive species attributed to ballast water release and transoceanic shipping in general have been recorded in the Great Lakes. The study, led by Fisheries and Oceans Canada scientist Dr. Sarah Bailey, was published on March 9, 2011 in the Journal of Environmental Science and Technology.
Managing aquatic invasive species
Aquatic invasive species cost Canada and the United States hundreds of millions of dollars each year. Most are difficult, if not impossible, to eradicate once they are established in lakes, rivers and other aquatic systems. For this reason, the most effective way to limit their spread is to prevent their introduction in the first place. One of several ways to reduce the risk of non-native species introductions into Canadian waters is through the management of ballast water on ships.
To ensure stability on the water, most large commercial vessels have ballast tanks that can be filled with water or emptied to safely balance the weight distribution of their load or to compensate for reductions in cargo or fuel. However, ballast water taken on board in one port may be released in another port, inadvertently releasing non-native species that the water may contain. Historically, ballast water was considered to be the largest single source of introduced aquatic invasive species in Canada's waterways.
Between 1959 and 2010, at least 56 non-native aquatic species were reported in the Great Lakes, with 34 of those attributed to transoceanic shipping. For example, ballast water is the original vector1 by which Zebra and Quagga Mussels, Tubenose and Round Gobies, Spiny Water Fleas and Bloody Red Shrimp were transported to the Great Lakes. Since their original introduction, these aquatic invaders have been spread further through river systems and from lake to lake by other means such as on fishing equipment, in bait buckets, or on the hulls of recreational boats that may not have been cleaned properly.
Between 1959 and 2010, at least 56 non-indigenous aquatic species were reported in the Great Lakes, with 34 of those attributed to transoceanic shipping.
For example, ballast water discharge from vessels is the original vector by which Bloody Red Shrimp, Zebra Mussels, Round Gobies and other invasive species were introduced to the Great Lakes.
They have since been spread further by other means.
Ballast water management in the Great Lakes
Invasive plants and animals from foreign freshwater ports are those most likely to thrive in the fresh waters of the Great Lakes. Ballast water exchange, where ships' crews exchange coastal port water in ships' ballast tanks with oceanic salt water during the voyage, is used to reduce the risk of species invasions by physically removing coastal organisms from the tanks. Second, the high salinity of the ocean water would be inhospitable for many coastal organisms that were not removed from tanks. Third, any marine organisms drawn into the ballast tanks along with salt water in mid-ocean are unlikely to survive if released in a coastal port. Used globally, ballast water exchange is particularly effective for reducing the risk of invasion to freshwater ports like those in the Great Lakes.
Between 1989 and 1993, ballast water exchange was voluntary. In 1993, it became mandatory for ships destined for the Great Lakes to exchange ballast water loaded at or near a port with salt water from mid-ocean (at least 200 miles offshore and in water at least 2,000 metres deep).
In 2006, Canada added a new measure for ships with empty ballast tanks to help prevent the arrival of non-native species. In addition to mid-ocean ballast water exchange, the new regulations require that empty tanks be flushed or rinsed in mid-ocean to make sure any leftover organisms are also given the salt water treatment.
These regulations are supported by intensive inspection and compliance efforts. All vessels entering the St. Lawrence Seaway from outside Canada’s Exclusive Economic Zone are inspected by Transport Canada or the U.S. Coast Guard under a unique bi‑national inspection program when they reach the Port of Montreal. Annually, no more than three percent of vessels are non-compliant, and all of these ships are required to take corrective actions before proceeding. The program has been heralded around the world as a model of effective management and bilateral regulatory cooperation.
Examining policy effectiveness
The ballast water requirements pioneered in the Great Lakes have become regarded as best practices that are being incorporated into international ballast water guidelines. As the world begins to consider the next steps in ballast water management, there is a need to fully understand the effectiveness of ballast water exchange and flushing.
For the past several years, Fisheries and Oceans Canada has worked closely with various levels of Canadian and U.S. governments to examine how effective existing ballast water policies are at keeping invasive species out of the Great Lakes. Co-authors of the study include scientists from Transport Canada and the Canadian Aquatic Invasive Species Network, a national network of Canada's leading researchers in the field of aquatic invasive species. Following international peer review, the study results were published in the highly respected journal, Environmental Science and Technology.
"The four lines of evidence that we examined in this study indicate that ballast water exchange and flushing, coupled with the intensive inspection program provides robust, but not complete, protection against ship-mediated biological invasions into the Great Lakes system from foreign ballast water," says Dr. Bailey.
The researchers used four types of evidence to assess the efficacy of the regulations:
Is saltwater ballast water exchange and flushing demonstrably effective?
Ballast water exchange and flushing is designed to remove most freshwater organisms and kill the remaining ones. The first line of questioning was to confirm that the practices really work as planned, under tightly controlled conditions.
Comprehensive studies in the laboratory and onboard transatlantic ships revealed that saltwater ballast water exchange and tank flushing do effectively decrease the number of viable propagules (living organisms that could potentially start a population) in ballast tanks.
Is saltwater ballast water exchange and flushing effective under operational conditions?
To determine if exchange and flushing are as effective when scientists are not instructing the vessels, Dr. Bailey's team asked whether the average commercial vessel arriving to the Great Lakes has lower numbers of living organisms in its managed ballast tanks than would otherwise be expected.
Random sampling of incoming ships confirmed that ballast water exchange and flushing reduces the number of ships carrying a lot of individual organisms in their ballast water. "Also, the practice virtually eliminates high-risk freshwater organisms because the exchange replaces freshwater species from the source port with saltwater species. These have a much lower chance of surviving when discharged into the freshwater of the Great Lakes," says Dr. Bailey.
Can compliance be achieved on a broad scale?
The process only works if vessels follow the rules. Having shown the process is effective and works on regular commercial ships, the next step was to determine if all ship operators are in fact exchanging their ballast at sea as required.
The study found that compliance rates by the general vessel population were very high, perhaps as a direct result of intensive inspection by federal agencies.
Are desired changes observed in the environment?
The final question was to determine if the rate of species invasions has decreased since the introduction of the ballast water policy.
Prior to the introduction of the regulations, the rate of aquatic invasions in the Great Lakes was estimated to be one new invader every eight months. The study determined that the rate of discovery of new aquatic invasive species has been declining since 1995, and no new species attributed to ballast water have been recorded in the Great Lakes since 2006. The co-authors caution that discovery rates of aquatic invasive species can be affected by imperfect data due to time lags, taxonomic bias and insufficient data. While discovery rates alone cannot be used to evaluate the regulations, the four lines of evidence combined indicate that the ballast water program on the Great Lakes is extremely effective.
"Extensive inspection and enforcement efforts have been critical to the success of this program and need to be maintained to have confidence that exchange and flushing continue to work," says Dr. Bailey. "This is the case for any new environmental regulations… inspection and enforcement is necessary to ensure that environmental policies translate into increased environmental protection."
Results of this study indicate that mid-ocean ballast water exchange and flushing, coupled with an intensive inspection program provide a similar level of environmental protection to freshwater ports as expected under the International Maritime Organization's (IMO) proposed standards for ballast water - standards that are not anticipated to be implemented on all vessels until 2016. In the meantime, Dr. Bailey and her colleagues will continue to conduct research to identify vectors of aquatic invasions to the Great Lakes, as well as to develop strategies to minimize risk.
For more information on Aquatic Invasive Species:
Aquatic Invasive Species: An overview
A Canadian Action Plan to Address the Threat of Aquatic Invasive Species
Canadian Ballast Water Program
Canadian Aquatic Invasive Species Network (CAISN)
Centre of Expertise for Aquatic Risk Assessment
Aquatic Invasive Species Identification Booklet -Eastern Canada
1 Vector – The physical means by which a species is transported from one area to another, usually referring to transport by humans.