Ships have allowed humans to navigate the world for the purposes of exploration, travel, and trade. But all too often, we inadvertently allow aquatic stowaways to hitch a ride aboard our vessels. When ships enter new territories and discharge ballast water, they also release huge numbers of marine organisms—ranging from microbes and mollusks to crabs and comb jellyfish—into new waters. The purpose of the BWM Convention is to prevent the damaging effects these non-native species can have.
Alien species: What are the risks?
Invasive alien species are defined as species that have been introduced to an environment that is not their own. Once there, they modify their new ecosystem or habitat, or harm other species around them. While some alien species may quickly die off in their new habitat, others can thrive due to the lack of natural predators that would normally control their population. The effects of this can be devastating for the local environment. As they grow in number, invasive species compete with native flora and fauna for food or space, wreaking havoc on the environment and threatening to destroy biodiversity.
There are currently over 14,000 invasive alien species recorded in Europe, with more than half originating from outside EU countries.
The effects of untreated ballast water are well documented. If left unchecked, the resulting explosions in population of non-native organisms can wipe out native species, disrupt the food chain, interfere with infrastructure by incapacitating power plants, disrupt water supply, and spread deadly diseases.
5 aquatic invasive species at a glance
- Northern Pacific sea star (Asterias amurensis): Native to the coasts of northern China, Korea, Russia, and Japan, this starfish has invaded the southern coasts of Australia. The sea star has a huge appetite and will eat a wide range of other organisms, and therefore poses a threat in its new home—specifically by eating the eggs of the endangered handfish. It also tolerates a wide range of temperatures and water salinities and can carry up to 20 million eggs, giving it the potential to spread far and wide.
- European green crab (Carcinus maenas): As the name suggests, this green crab (also known as a shore crab) originally came from Europe. However, it is highly adaptable and has now colonized Southern Australia, South America, South Africa, and coastlines in the United States. It is responsible for seriously depleting native species. According to the IMO, green crab has cost the American fishing industry millions of dollars.
- Zebra mussels (Dreissena polymorpha): The zebra mussel not only spreads via larvae in ballast water; it can also hitch a ride by attaching itself to ships and other solid objects. As well as decimating native fish populations and promoting the growth of poisonous algae, the zebra mussel can also damage water treatment plants by clogging pipes in the water. When attached to vessels, the mussels increase ship resistance, which significantly impacts both fuel costs and emissions. If left alone for too long, they can increase corrosion of steel and concrete, making equipment and infrastructure more susceptible to failure.
- Comb jelly (Mnemiopsis leidyi): Despite moving incredibly slowly, the comb jelly (or “sea walnut”) is one of the most notorious invasive species. Via ballast water, the comb jelly has managed to invade numerous non-native environments, including the Black Sea, Caspian Sea, and the Baltic and North Seas. Capable of eating ten times its body weight, it has had a severe detrimental impact on the fishing industry.
- Cholera (Vibrio cholera): It’s not only larger organisms that are causing problems. Bacteria such as Vibrio cholera can quickly spread via ballast water, posing a serious threat to humans if ingested via drinking water or seafood. In fact, a cholera outbreak caused by ballast water discharge led to 12,000 deaths in Latin America.
Prevention is the shipping industry’s responsibility
It is clear to see that the industry must address the issue of untreated ballast water. Controlling introduced populations is a difficult and extremely expensive task—and complete eradication may even be impossible. Therefore, preventing the introduction of invasive species is therefore the best way to address the issue.
Ballast water management systems (BWMSs) can minimize the risk of such species spreading. While purchasing, implementing, and operating a BWMS may cause a headache for shipowners, compliance with the new regulations is imperative. Only in this way can the shipping industry help protect the oceans, the economy, and most importantly: people.