Ships, especially larger vessels, need to carry ballast water to ensure stability, trim, and structural integrity during voyage. Their ballast tanks are filled or emptied in order to adjust the amount of ballast force by taking up local water upon cargo discharge (light-load state) and discharging it again upon cargo reload (medium/ heavy-load state). This way, small aquatic organisms, including bacteria and other microbes, micro-algae, as well as various life stages (i.e. eggs, cysts, larvae) of aquatic plants and animal species, are transported from port to port, often across thousands of sea miles, and introduced to entirely new environments. Ballast water thus represents a major vector for aquatic invasions all over the world.
Invasive aquatic species
Species are considered ‘alien’ (also: exotic, non-native, non-indigenous) if they are not native to a given ecosystem, and ‘invasive’ when their introduction to a new environment causes (potential) harm to ecosystems, the economy, or human health. Not many invasive species manage to adapt to their new environment, but once they become established, they are virtually impossible to eradicate and often easily outcompete local species. According to the UN, invasive species dispersed by ballast water discharges represent one of the four main threats to the world’s marine ecosystems, with increasing damage potential due to the expanding volume of seaborne traffic. Notorious examples of aquatic invaders include the green alga Caulerpa taxifolia, the zebra mussel Dreissena polymorpha, and the comb jellyfish Mnemiopsis leidyi, as well as the bacterial pathogen Vibrio cholerae, the causing agent of the Cholera disease.
In 2004, following many years of negotiations, the International Maritime Organization (IMO) adopted the ‘International Convention for the Control and Management of Ships Ballast Water and Sediments’, a body of regulations and guidelines for the effective prevention of species dispersal by ballast discharges. The Convention will require all ships to carry out ballast water management and documentation procedures to a given standard, with the option for signing States to take additional measures. It will enter into force 12 months after ratification by 30 member States, representing 35% of the world’s merchant shipping tonnage.
The Knutsen Ballast Water Treatment System is a cost-effective, environmentally friendly and user-optimized system for the cleaning of ballast water based on a pressure/vacuum-procedure combined with UV radiation. After successful completion of both the land-based and ship-board test phases, KBAL® received Type Approval by Det Norske Veritas in November 2012 and is now available for installations.
Flow Cytometry is a laser-based technology that simultaneously measures and then analyzes multiple physical characteristics of single particles, usually cells, as they flow in a fluid stream through a beam of light. The properties measured include a particle’s relative size, relative granularity or internal complexity, and relative fluorescence intensity. These characteristics are determined using an optical-to-electronic coupling system that records how the cell or particle scatters incident laser light and emits fluorescence. Modern flow cytometers are able to analyze thousands of particles per second, in ‘real time’, and can actively separate and isolate particles based on specific properties. (Source: BD Biosciences)