A ship discharges ballast water. Since 2017, IMO regulations require vessels to treat their ballast before discharge so that invasive species cannot harm ecosystems.

Ships move all sorts of amazing, useful and vital commodities around the globe making the world a much smaller place. All year round, Icelanders can enjoy mangoes from Thailand and the Japanese can sip champagne from France

As the International Chamber of Shipping says: “Without shipping, the import/export of affordable food and goods would not be possible – half the world would starve and the other half would freeze!”

Ships carry all the things we love and need but also, inadvertently, give lifts to all sorts of aquatic species in their ballast water tanks.

Ballast is water – fresh or seawater – taken on by a ship and stored in tanks to improve the vessel’s stability and increase its performance, especially when carrying little or no cargo or in rough seas.  According to Marine Insight (www.marineinsight.com) it has been integral to ship stability since steel-hulled vessels were introduced, as it “reduces stresses on the vessel’s hull, balances off for the weight loss due to consumption of water and fuel, provides better manoeuvrability with sufficient vessel draft, including ship propeller immersion, and also helps in improving living conditions of the crew aboard by reducing vibrations and uncontrolled vessel’s movements.”

Living in this water, however, are numerous marine microorganisms, phytoplankton, zooplankton. These organisms pose no problem if they remain in their intended, or ‘native’ region, but when they are moved around these same species are regarded as ‘non native’ species. Most cannot tolerate the new environment in which they are deposited, but certain species have shown themselves to be particularly adaptable and become invasive and harmful to their new habitat, outcompeting native species for resources. Examples include zebra mussels, green crabs and mitten crabs.

When a vessel leaves a port it often takes on or pumps out ballast depending on its cargo, and will likely carry out the operation as it leaves port. The truly global nature of shipping enables non-native marine species to be deposited all around the world, threatening the globe’s diverse marine ecosystems.

According to ballast water management system provider Erma First, “Invasive aquatic species are one of the four greatest threats to the world’s oceans and can cause extremely severe environmental, economic and public health impacts”. (www.ermafirst.com)

One sensitive marine ecosystem is off the coast of Alaska on the left coast of North America. So far, many invasive species that have made their way to other ecosystems have yet to reach Alaska, but a 2016 paper published by Alaska Pacific University (www.sciencedirect.com/science/article/pii/S0308597X16302044), says: “…the relatively uninvaded coastline of Alaska currently faces a heightened risk of novel biological introductions as a result of increasing regional traffic, climate change, emerging Arctic trade routes, and development”.

Vessels arriving at the US states main port, Port of Alaska, come from across the globe. According to the Observatory for Economic Complexity (https://oec.world/en/profile/subnational_usa_state/ak) in 2020, the top importing countries to Alaska were South Korea, Canada, Thailand, Vietnam and Malaysia.

MarineTraffic data shows that between January and June this year 273 vessels called at an Alaskan port. Whilst the majority were arrivals from the US, most notably the west coast port of Tacoma, there were also 27 vessels from South Korea, nine from China and three from Japan.

Of these vessels, 129 were wet bulk, most likely related to its biggest import of petroleum products, 91 were containers and 52 were dry bulk.

To protect areas such as Alaska the International Maritime Organization (IMO) has been tasked with containing the movement of invasive species. In 2004 introduced the International Convention for the Control and Management of Ship’s Ballast Water and Sediments or just Ballast Water Management Convention (BWMC), which came into force in 2017.

Meanwhile, the US introduced its own rules which came into force in 2013. BWMS manufacturer Erma First was the first to gain approval for its system by the United States Coast Guard.

A BWMS filters and treats the water with chemicals or ultraviolet light, killing organisms before the water is discharged from the ship.

To curb the spread of invasive species a unified approach to responsible ballast water management was called for. IMO’s Ballast Water Management Convention was rolled out amidst many challenges, but to date has garnered signatures from 63 states representing 68.51% of world merchant shipping tonnage (www.imo.org/en/MediaCentre/PressBriefings/Pages/21-BWM-EIF.aspx).

With the majoring of the world’s tonnage onboard it may be that Alaska’s native aquatic species will be free to thrive unhindered by ballast water stowaways.