Biofouling: a deep dive into the dirty world of shipping


Marine biofouling is destroying the environment. It makes ships more polluting, gives invasive species a free ride across the world to cripple fragile ecosystems and it costs the shipping industry over £100 billion per year. The antifouling coatings applied to protect ships from biofouling tend to be toxic, shed microplastic particles, and often have strict disposal regulations – which perversely leads to most ship recycling taking place on just three beaches in South Asia where such regulations can be best avoided, to the detriment of workers’ safety.

Biofouling happens when organisms such as bacteria, algae, and barnacles build up on unwanted surfaces, like underwater cables or hydropower turbines. When fouling occurs on ships it can dramatically increase the frictional drag they experience, meaning they consume up to 45% more fuel. This is particularly harmful as most large vessels are powered by Heavy Fuel Oil, which is extremely polluting.

Biofouling happens when organisms such as bacteria, algae, and barnacles build up on unwanted surfaces

We don’t often think about the shipping industry. Even the fervent post-Brexit discussions of UK trade hardly mentioned it, focusing instead on queues of lorries and threats to the automotive industry. Nevertheless, whether we notice it or not shipping has a massive impact on our day-to-day lives. Over 95% by volume of imports to and exports from the UK travel by sea, including oil, food, and medicines. We are an island nation after all, but worldwide the figure is still around 80%. To facilitate this there are over 60,000 ships in the world’s merchant fleet – that’s a lot of hull to foul.

Organisms don’t just settle randomly; marine biofouling is a structured hierarchical process. Within a few minutes of immersion, a conditioning film of organic molecules (mainly proteins and glycoproteins) will have formed on the ship’s surface. As the name suggests, this film ‘conditions’ the surface to make further attachments easier.

Within hours bacteria will attach to the surface, and if the conditions are right these bacteria will initiate biofilm formation to permanently adhere. Microalgae, diatoms and other microorganisms will attach to the biofilm after a few days, followed by the settlement of macroalgae, animal larvae and finally adult marine organisms like barnacles and tubeworms. In total, there are over 4,000 different biofouling species in the ocean and together they form complex ecosystems on submerged surfaces.

Within hours bacteria will attach to the surface, and if the conditions are right these bacteria will initiate biofilm formation to permanently adhere

In the age of globalised trade, ships can transport these miniature marine ecosystems thousands of kilometres from their usual spots, sometimes to vast-yet-fragile environments where they can cause untold harm. Creatures hitching a free ride on ships’ hulls have been recognised as an important source of non-indigenous species to many nations’ waters, including Australia, Japan, and the US. In New Zealand, where the marine environment is recognised as a global biodiversity hotspot, 87% of invasive marine species are suspected to have arrived due to ship biofouling.

To counter biofouling, ships tend to be equipped with antifouling coatings. The ancient Phoenicians are credited with devising the earliest antifouling coatings around 700BCE – attaching large lead sheets to cover their wooden ships. Unfortunately, most antifouling technology is still similarly toxic over 2,700 years later. Modern biocidal antifouling coatings usually contain a copper-based biocide which is released into the surrounding water to kill biofouling organisms. These coatings are also usually polymer-based, meaning they shed microplastic pollution into the oceans. Recent research has shown that these biocidal antifouling paint particles are toxic to sediment-dwelling organisms like cockles and ragworms and remain so for decades.

At the end of a ship’s life the toxicity of these coatings presents further problems, with increased regulation of ship recycling in the Global North increasing recycling costs – and fuelling more dangerous practices in developing nations. Every year around 800 ships reach the end of their lives, and research from the NGO Shipbreaking Platform indicates that around 70% of these are broken up on just three beaches in India, Pakistan and Bangladesh. More than 400 deaths have been recorded on these beaches since 2009, with the International Labour Organization classifying shipbreaking as one of the world’s most dangerous occupations. Child labour is also rife, with research suggesting 13% of workers in Bangladesh are under the age of 18.

Despite the EU recently implementing strong ship recycling regulations – and the UK keeping those regulations following Brexit – very little seems to have changed in practice. This is in large part due to the ‘flags of convenience’ phenomenon, whereby ships are flagged (and therefore follow the rules of) a country different from their country of ownership. This means international collaboration is vital. Until then, developing safer antifouling coatings could go a long way to improving the lives of workers in developing nations and protecting Earth’s marine life.

Image: Kereplaz via Flickr

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