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Science Response 2020/053

Additional Analyses of Ballast Water Management Scenarios to Reduce the Establishment of Harmful Aquatic Species Across Canada and the Great Lakes


The International Maritime Organization’s International Convention for the Control and Management of Ships’ Ballast Water and Sediments, 2004 (the Convention) establishes global ballast water management regulations for ships to address risks of spreading harmful aquatic organisms and pathogens in ballast water and sediment (IMO 2004). The Convention entered into force in September 2017 and, in turn, parties to the Convention are expected to implement the Convention’s ballast water regulations in waters under their jurisdiction. This includes the implementation of a ballast water performance standard (Regulation D-2 of the Convention), which sets limits on the concentration of viable organisms in discharged ballast water. Most ships will adhere to the D-2 standard by using a type approved ballast water treatment system (hereafter referred to as treatment), which utilizes wastewater treatment technologies such as filtration (e.g., screen or disc filters) and disinfection (e.g., ultraviolet radiation, chlorination) processes (Mouawad Consulting 2013). The D-2 standard will replace the currently widespread management method of ballast water exchange (hereafter known as exchange; Regulation D-1), which is the process of discharging ballast water at sea and refilling ballast tanks with oceanic water in an effort to reduce the abundance of high-risk coastal or freshwater organisms. Parties to the Convention also retain the right to impose more stringent requirements for ballast water than those required by the Convention (Art. 2.3; IMO 2004). In 2010, Canada proposed that utilizing exchange plus treatment may provide greater protection against the establishment of harmful species than treatment alone, at least for freshwater ports (IMO 2010).

The Convention applies to international shipping (whether transoceanic or regional), as well as domestic ships that pose a risk to the environment, human health, property and resources. Studies indicate that ballast water moved by Great Lakes ships also introduce nonindigenous species (Briski et al. 2012, Adebayo et al. 2014, Cangelosi et al. 2018). Within the Great Lakes, at least 7 nonindigenous species and 21 indigenous species were transported in ballast water to ports outside of their historical distribution within the region (Briski et al. 2012, Cangelosi et al. 2018). Additionally, Great Lakes ships typically transport a higher organism abundance in ballast water than their transoceanic counterparts because survival is higher on shorter voyages (Rup et al. 2010, Briski et al. 2012, Adebayo et al. 2014). Given that Lakers transport at least 68 million tonnes of ballast water annually and account for 95% of the ballast water moved within the Great Lakes region (Rup et al. 2010), empirical evidence indicates that Lakers play a major role in the dispersal of nonindigenous species within the region.

Canada, a party to the Convention, is currently updating its ballast water management regulations to (i) fulfill its international obligations and (ii) minimize the risk of introducing and spreading harmful aquatic organisms and pathogens through ballast water. Transport Canada’s proposed regulations would require ships originating from international waters to use exchange plus treatment to manage ballast water when travelling to Canadian freshwater ports (excluding U.S. transits within the Great Lakes), at least until September 8, 2024 (Canada Gazette 2019). Ships travelling to any other Canadian port would be required to meet the D-2 standard, including domestic ships and Lakers. The proposed regulations are subject to change following the Canadian federal regulatory development process — any modification of details such as timelines and applicability could result in changes to expected efficacy of the regulations.

This study is a follow-up to a previous study (Drake et al. 2020), which used a multi-stage model to estimate the establishment rate of nonindigenous and harmful species in Canada under various ballast water management scenarios, with the objective to determine the effectiveness of exchange plus treatment compared to exchange or treatment alone. Building on the model from Drake et al. (2020), this study estimated the establishment rate for additional ballast water management scenarios, to address the science questions below, following a formal science advice request from Transport Canada:

  1. When compared to exchange or treatment, to what extent would requiring ships traveling to Canadian freshwater ports to perform exchange plus treatment reduce the establishment risk of nonindigenous or harmful species in Canada?
  2. Relative to the above-mentioned scenario, what is the expected reduction in establishment rate across Canada if exchange plus treatment was only required for ships traveling to either the Great Lakes only or Great Lakes and St. Lawrence River (GLSLR; see Table 1 for details)?
  3. To what extent would the utilization of treatment systems on domestic transits within the GLSLR reduce the risk of spreading nonindigenous species among Canadian ports or throughout the entire GLSLR region, and what is the predicted effect on establishment risk if treatment systems are utilized depending on various factors?
  4. What is the expected reduction in establishment risk if ballast water is treated using treatment systems on domestic transits across Canada?

Because Great Lakes ships operating binationally between Canada and the U.S. do not undertake ballast water exchange, they are considered along with domestic ships for the purpose of this science advice request.

This Science Response Report results from the Science Response Process of August 10–11, 2020: Additional Analyses of the Effectiveness of Ballast Water Exchange Plus Treatment as a Mechanism to Reduce the Introduction and Establishment of Aquatic Invasive Species in Canadian Ports.

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