Managing risk of non‐indigenous species establishment associated with ballast water discharges from ships with bypassed or inoperable ballast water management systems

Abstract

Ballast water is recognized as a leading pathway for the introduction of aquatic non‐indigenous species which have caused substantial ecological damage globally. Following international regulations, most international ships will install a ballast water management system (BWMS) by 2024 to limit the concentration of aquatic organisms in ballast water discharges; however, these new technologies may not operate as expected at global ports having variable water quality or may periodically malfunction. Using simulations informed by empirical data, we investigated the risk of non‐indigenous species establishment associated with BWMS inoperability and evaluated potential mitigation strategies. Scenarios considered included bypassed or inoperable BWMS achieving no reduction in organisms, and partially functioning BWMS with discharged organism concentrations exceeding permissible limits. These scenarios were contrasted to outcomes with fully functioning BWMS and to voyages where ballast water exchange (BWE) was used to mitigate risk. Partially functioning BWMSs were nonetheless beneficial, reducing organism concentrations in ballast and thus establishment risk. When a BWMS is bypassed or partially functioning, BWE is a useful emergency mitigation measure, reducing establishment risks more than partial BMWS. However, the greatest risk reduction was achieved when partial BWMS and BWE were combined. Voyage‐specific characteristics such as concentration of organisms at uptake and destination port salinity can affect the optimal management strategy for voyages when the BWMS does not achieve compliant discharges. Synthesis and applications. The risk of aquatic invasions and their associated ecological damages can be substantially reduced by using a ballast water management system (BWMS) and/or ballast water exchange (BWE). When a BWMS is inoperable, appropriate mitigation measures should be decided on a trip‐by‐trip basis considering voyage route and reason for BWMS inoperability (when known). BWE is a useful strategy for reducing invasion risk, except when uptake concentrations are very low. Combining BWE and partial BWMS always reduced risk compared with BWE alone, but did not greatly reduce risk when uptake concentrations were high.

Incorporation of colonization pressure into the propagule pressure‐based global ballast water standard

“…To model establishment risk, first, we determined population sizes from discharge volumes obtained from Bradie et al (2022), which consisted of 10,000 recorded ballast water discharges that ranged from 20 to 1,060,620 m 3 (13,871 ± 25,738, mean ± standard deviation). We used volumes from 29 vessels sampled in Atlantic (Halifax, Hamilton, Saint John, Sorel) and Pacific (Vancouver) ports in Canada in 2017 and 2018 by Fisheries and Oceans Canada as a reference for empirical community composition in treated ballast water (Bailey et al, 2022).…”

Biological testing of ships’ ballast water indicates challenges for the implementation of the Ballast Water Management Convention

“…In addition, the abundance of living ≥50µm -sized organisms in non-compliant samples reached thousands of organisms m -3 several times, indicating that living organisms in the largest organism category may have been more resilient to ballast water treatment. Alternatively, the observed non-compliances may be associated with tank contamination, potentially due to several factors, such as insufficient crew training in operating and maintaining the BWMS, issues with connecting pipework and valves of the ship (e.g., valves malfunctioning, or not completely closed), bypass of the BWMS pumping untreated water into the ballast tanks, or inadequate ballast tank cleaning to remove all sediments at the time of BWMS installation (C ̌ampara et al, 2019;Gerhard et al, 2019;Bradie et al, 2023). In four out of five non-compliant commissioning tests included in the present study, non-compliance was due to tank contamination (presence of ≥50µm organisms living in the sediments) or malfunctioning ship valves allowing seepage of untreated ballast water from connected tanks (Stephanie Delacroix, unpublished data, September, 2023).…”

Modification of Ballast Filtering Device on John Lie Training Ship to Prevent Marine Pollution

“…This can also have an impact on the imbalance of marine ecosystems and adversely affect the marine life development (Bailey et al, 2022). The impact of the foreign species development at sea by the IMO is considered more difficult to overcome than the impact of pollution due to oil spills and has become a global problem that requires more serious attention from the entire world maritime community (Bradie et al, 2023;Casas-Monroy & Bailey, 2021;Čulin & Mustać, 2015).…”