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In addition to the six MARPOL Annexes, IMO conventions address antifouling systems used on ships, the transfer of alien species by ballast water and the environmentally sound recycling of ships.  


Biofouling: The accumulation of organisms where it is not wanted on surfaces such as ship hulls.  

Biocide: Substance that kills living organisms 

Tributyltin (TBT): Toxic biocide embedded in self-polishing anti-fouling paint.  

Invasive Species: Alien species that is introduced to a new region that does not have natural predators allowing its population to grow exponentially.  


The settlement and growth of organisms on the hull of ships, biofouling, is a problem as old as man sailing the seas. Marine organisms growing on the ship´s hull include microorganisms such as algae, shellfish larvae, or seaweeds, barnacles, sponges, and more. Fouling leads to increased fuel consumption up to 15%, lower sailing speeds and lower maneuverability. Biofouling communities can also be found on docks, marinas, fences, and other hard surfaces in the water. 

The introduction of alien species has been identified as one of the four greatest threats to marine ecosystems.  When an alien species is introduced into a new region it may establish a population. Often, the newly introduced species does not have natural enemies and its population can grow without limitsOnce established, an invasive species is difficult to get rid of and the far-reaching effects on marine ecosystems are irreversible in most cases. The largest source for the global introduction of marine invasive species is shipping. Species migrate by traveling in ballast water tanks, on ship hulls or other locations on the ship.   

Ships have an average life expectancy of 25-30 years (Mikelis 2008). After that they are replaced by new, technologically more advanced ships. In 2020, 630 end-of-life vessels were recycled (Shipbreaking Platform Website). Up to 97% of all the ship material collected in dismantling is re-used in onshore industries: hence the term ship recycling. But ships also contain many hazardous and toxic materials that should be handled with care when dismantling a ship such as oil, sludge, paints, heavy metals, ozone depleting substances, and asbestos.  

Dive Deeper

Antifouling Systems

Over time, different systems have been used to stop organisms growing on the ship’s hull. During the 1960s, a highly effective solution was found: a biocide called Tributyltin (TBT). It was embedded in a self-polishing anti-fouling paint. TBT has since been described as the most toxic substance ever deliberately introduced into the marine environment. Besides killing fouling organisms, TBT proved to be harmful for a great number of marine species, specifically shellfish species, such as the dog whelk.  

While TBT is banned by the antifouling convention, many antifouling paints used today also contain toxic substances, such as copper, zinc, and (agricultural) pesticides.  Several antifouling systems are developed that do not use biocides, including:  

  • Non-stick coatings: organisms cannot attach to very smooth surfaces  
  • Technical systems based on creating an electrical powered field or vibrations 
  • Prickly coatings: covering the ship hull surface with hairs or tiny spines  

Invasive species can also damage human health, including a deadly condition called paralytic shellfish poisoning (PSP). PSP can be induced by toxic algae in red tides that contaminate mussels and other shellfish, which are eaten by humans. Invasive species can also facilitate the spreading of viruses, such as the Cholera bacteria.  

Invasive Species

Invasive species can have serious impacts on ecology, economy, and human health. They can affect infrastructure such as the golden mussel in Brazil where large quantities of clustered mussels are clogging hydropower plants. The comb jelly in the Black and Caspian Sea has impacted the fishing industry due to its consumption of larvae and zooplankton that are food for native fish species.

Ship Recycling

Ship recycling is labor intensive, and most ships are recycled in countries where labor is cheaper and national laws are less strict. The leading five states in terms of numbers and tonnage of ships recycled are India, China, Pakistan, Bangladesh, and Turkey (Mikelis 2008). 

Many ship recycling ‘yards’ on the Indian sub-continent are tidal beaches. Ships are beached by grounding them at high tide, which leaves them stranded at low tide. This is referred to as ‘the beaching method’. Local people dismantle the beached ships by hand, often under dangerous and polluting circumstances. These unregulated dismantling operations where protective equipment, heavy machinery and training are lacking often lead to health problems, injuries, and death.  

What can you do?

The antifouling, ballast water and ship recycling conventions require companies to use procedures and technical installations on board in order to minimize the negative impacts of antifouling systems, the introduction of invasive species and the recycling of ships. As a seafarer or port employee, you can contribute by following the procedures and using the technical means available to you. 

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