Ballast has been used to maintain stability and seaworthiness of cargo ships dating back to timber-hulled sailing ships and their use of solid ballast. Water as ballast was widely introduced in the use of metal-hulled steam powered ships, where water carried to generate steam could also be used as ballast to trim and maintain stability of the ship. Today’s modern large cargo ships can have a ballast capacity in excess of 5,000m³ or 5,000 tons of water.  

Unfortunately, this widespread and efficient practice often has an unintended consequence. It is estimated that the wider shipping industry transports up to 5 billion tons of water and circa 10,000 unwanted species annually. This essential water needed for the safe operation of ships can pose a significant risk to indigenous marine life through the unintentional transportation of marine life around the globe through shipping routes resulting in the bio-invasion of non-indigenous marine organisms with possible dire consequences for the local marine life. 

Importance of ballast water management   

Ecological impact 

Ballast water which is taken on board by ships to ensure safe operation and maintain stability will often contain a wide variety of microbes, bacteria, small invertebrates and other marine organisms. As ballast water is discharged at different ports around the globe, relocated marine organisms may establish themselves in the new location and disrupt the existing marine ecosystem. They become an invasive species, displacing the native species resulting in loss of biodiversity.  

Economic impact 

Invasive species transported within ballast water which establish themselves and disrupt the existing marine ecosystems can result in significant consequences for the local economy, in particular the local commercial and leisure fishing industry. By competing with native marine species, these invasive marine organisms put additional drain on food sources and habitat that can result in declining fish stocks and other marine life, impacting on the local economy. In addition, invasive species produce a detrimental effect to marine infrastructure by destabilising embankments and obstructing water intakes/outlet pipes.   

Heath impacts  

Marine organisms transported in ballast water also have the potential to impact human health, both directly and indirectly, through the spread of harmful algae blooms and pathogens resulting in harm to humans through direct contact or potential contamination of drinking water supplies. 

Ship operations 

Prevention of the transportation of marine organisms is by far the most effective strategy for tackling the risk of introducing invasive species into an existing ecosystem. Prevention is much less costly and more successful than attempting to eradicate an identified invasive species. Affecting 99% of the global fleet, the Ballast Water Management (BWM) Convention requires vessels to manage their ballast water on every voyage as of September 2024.  

• All ships are required to have an approved BWM plan and ballast water record book on board
• All ships of >400 gross tonnes must be surveyed, issued with an International Ballast Water Management Certificate of a Ballast water Management Certificate of Compliance.

Port operations 

Climate change impacts 

The well documented changes in climate relating to water temperature and water chemistry can not only affect the assets, infrastructure and operation that are essential to service ports and terminals. It can also have a negative effect on the marine ecosystem by providing conditions for invasive species to thrive and displace native species and should be a consideration in the overall climate change risk assessment for ports and terminals. 

Monitoring 

Port Biological Baseline Surveys are an important step in the control of the transfer of harmful non-indigenous marine organisms transferred in the ballast tanks of ships from one marine ecosystem to another. A port biological baseline survey is a study of the port’s ecosystem, which identifies the abundance and spreading of invasive species. These surveys, if repeated on a regular basis can provide an important first warning of a potential issue as ports are the likely location for these non-indigenous marine organisms to arrive.  

The main purpose and benefits of undertaking port biological baseline surveys are. 

• Provide an overview of the current state of the local ecosystem with regards to the population of non-indigenous marine organisms and their potential effects on the native species and overall biodiversity. 
• Aid the development of the ballast water management strategies for the ships calling to port with regards to the risks associated with taking on ballast water in a particular port or region. 
• Build a baseline of data on the ecosystem and the effects of non-indigenous marine organisms so that biodiversity risks can be identified and mitigated

Summary 

International Maritime Organization (IMO) have already stated that the rate of invasion of these non-indigenous marine organisms is increasing and that the peak may not have been reached as volumes of sea traffic grows. Ships need to comply with the Ballast Water Management (BWM) Convention as the prevention of the transportation of marine organisms is by far the most important strategy in tackling the risk of introducing invasive species into an existing ecosystem and is much less costly. Ports can provide important insight through the implementation of Port Biological Baseline Surveys, not only for the local management of the port ecosystem, but also for the development of the calling ship’s ballast water management strategies.