Amendments to an international treaty aimed at preventing the spread of potentially invasive species in ships' ballast water entered into force on 13 October 2019. The International Convention for the Control and Management of Ships' Ballast Water and Sediments, 2004 (the BWM Convention) was adopted by the International Maritime Organization (IMO), a specialized agency of the United Nations, to address this problem. The BWM Convention entered into force in 2017. The amendments formalise an implementation schedule to ensure ships manage their ballast water to meet a specified standard ("D-2 standard") aimed at ensuring that viable organisms are not released into new sea areas, and make mandatory the Code for Approval of Ballast Water Management Systems, which sets out how ballast water management systems used to achieve the D-2 standard have to be assessed and approved. This will help ensure that aquatic organisms and pathogens are removed or rendered harmless before the ballast water is released into a new location – and avoid the spread of invasive species as well as potentially harmful pathogens.
Usually, ballast water is pumped into ballast tanks when a ship has delivered cargo to a port and is departing with less cargo or no cargo. Ballast water is then transported and released at the next port-of-call where the ship picks up more cargo. If a ship is receiving or delivering cargo to a number of ports, it may release or take on a portion of ballast water at each port. In such cases, the shipís ballast water contains a mix of waters from multiple ports.
The release of ballast water may introduce non-native organisms into the port of discharge. These introduced species, or bioinvaders, are also referred to as exotic species, alien species, and nonindigenous species. (Source: Massachusetts Institute of Technology Sea Grant - Ballast Water)