Ballast Water Invasive Species Calculator

Ballast water is seawater or freshwater pumped into a ship's tanks to provide stability when carrying little or no cargo. When ships discharge this water at a new port, any organisms living in it — including bacteria, plankton, fish larvae, and invertebrates — are released into a potentially non-native environment. This makes ballast water one of the primary vectors for introducing non-indigenous aquatic species globally.

The score combines five weighted sub-factors: propagule pressure (ballast volume and organism density), environmental compatibility (salinity and temperature match between ports), ecoregion similarity, port traffic intensity, and treatment efficacy. Each factor contributes up to 20 points, for a maximum score of 100. Higher scores indicate greater risk of a successful establishment event.

Propagule pressure refers to the number of individual organisms introduced and how frequently introduction events occur. Larger volumes of ballast water carry more organisms (higher introduction size), and ports receiving more vessel calls experience more introduction events — both increase the probability that at least some organisms survive and establish a self-sustaining population.

Yes, ocean exchange significantly reduces risk by replacing coastal organisms with open-ocean species, which are unlikely to survive in nearshore environments. It is estimated to achieve 95–99% flushing efficiency. However, it is less reliable than UV or combined treatment systems because complete exchange is difficult in rough seas, and residual organisms may remain.

The International Maritime Organization's Ballast Water Management Convention (BWM Convention, in force since 2017) requires ships to manage ballast water to meet one of two standards: the D-1 exchange standard (volume-based exchange) or the D-2 performance standard (discharge must contain fewer than 10 viable organisms per m³ ≥ 50 µm). Most new vessels must meet D-2 using an approved treatment system.

Most aquatic organisms are adapted to a narrow salinity range. A large salinity difference between source and destination ports creates an osmotic stress that kills most transported organisms before or shortly after discharge. A difference of less than 5 PSU is considered low barrier, while differences above 15 PSU significantly reduce survival probability.

Based on decision-support frameworks used by agencies like Fisheries and Oceans Canada, voyages scoring above 60/100 are considered high-to-very-high priority for active compliance monitoring and ballast water sampling. Scores of 40–60 are moderate priority, and scores below 40 are lower priority but should still comply with all applicable BWM regulations.

Not necessarily. Establishment depends on finding suitable habitat, food sources, temperature, salinity, and the absence of strong competition or predation. Ecoregion similarity is a key predictor — species transported between ecologically similar ports have a far higher probability of establishment than those moved between very different marine environments.