Do Ballast Water Management Systems Reduce Phytoplankton Introductions to Canadian Waters?

Global coastal aquatic ecosystems are negatively impacted by the introduction of harmful species through discharge ships’ ballast water. To reduce discharges organisms and pathogens, such as toxic phytoplankton species, ships now transitioning to use water management systems (BWMS) instead exchange (BWE). This study examines abundance diversity in managed BWMS (or a combination both BWE + BWMS) comparison those alone (collected from arriving Canada’s Pacific coast 2017–2018 2008, respectively). The were also examined relation key variables salinity age. Total was significantly lower preserved samples either or compared alone. Abundances higher than observed fresh (unpreserved) at time collection, with all meeting international limits for number viable ≥10 <50 μm minimum dimension (based on six 1-mL live counts). While there no apparent influence factors treatment type [e.g., ultraviolet (UV) chlorine], presence filtration, salinity, age, nor location last uptake abundances samples, power detect differences may be limited sample size. Ballast tended have although difference not statistically significant – additional research into community composition cells could valuable discriminate risk associated surviving treatment.