Big problems tend to start small, and true to this maxim, one the biggest problems in global shipping starts quite small indeed, with some remarkably weak forces at the atomic level.
Then, quite literally, it grows out of control.
But let’s first step back and get a glimpse of the big picture.
The global merchant fleet is huge, with more than 50,000 ships currently in active service, transporting around 90% of the world’s goods. This not only includes cargo delivered as the result of international online purchases, but even domestic shipping involves substantial use of national ‘marine highways’. Purchasing something in person? Chances are either the finished product, or the raw materials to make it, traversed a waterway at some point.
To get a sense of just how vast and how busy the global marine shipping industry is, take a look at Shipmap. It’s the result of a recent collaboration between the University College London Energy Institute and the data visualization company Kiln. The resulting interactive map is a mesmerizing amalgamation of 250 million data points from a full year of shipping data (2012).
Seen on this scale, it’s not so surprising to learn that the global fuel consumption associated with marine cargo transport is massive. Infact, it accounts for a significant share of the 3.9 million barrels of fuel per day used by all marine vessels.
According to the International Maritime Organisation, even if we exclude military, commercial fishing and recreational ships from the equation, merchant shipping accounts for approximately 2.5% of global CO2 emissions.
So, the last thing you’d want is something increasing the drag on these already laden ships, slowing them down and increasing fuel consumption just to get from port A to port B. Yet this is precisely what marine biofouling does.
Marine biofouling is the buildup of marine organisms on a submerged surface, and it’s a very big problem. Ship hulls are designed to glide through water in as streamlined a way as possible, but the gathering of algae, barnacles, mollusks and other marine life can undermine even the most inspired example of sleek naval architecture and can increase fuel consumption up to 40%.
It’s also a problem for structures that aren’t moving anywhere at all, causing corrosion and other structural damage to offshore platforms and underwater pipelines. It’s also the bane of most fisheries.
We tend to think of marine biofouling as a long time-scale problem, something that takes place on the scale of months to years. But as any seafarer will tell you, you can see the first effects within days, sometimes hours. Yet the biofouling process actually begins the instant the ship’s hull touches the water.
This is because organic molecules in the water such as proteins and sugars will adhere to the surface and are kept there through very weak interactions. Chief among theses are are Van der Waals forces, which involve the faint attraction atoms have to one another when they are in close quarters. These may be the weakest possible chemical interactions between molecules, a far cry less potent than the strong covalent forces within a molecule, yet without Van der Waals forces, life itself wouldn’t exist because what these gentle forces lack in individual strength, they make up in sheer numbers. Working together, they help hold proteins in the right shapes, and contribute to the stacking of nucleic acid base pairs in a DNA helix.
Along the hull of a ship, these weak interactions enable the formation of a fantastically thin biomolecular coating. This is where the whole problem of biofouling begins, because from there, life can take hold. Bacteria can find purchase in this coating, as well as diatoms and microalgae, forming a biofilm within days. Soon the larvae of macrofoulers take refuge in what is now essentially a microbial smorgasbord. From these larvae grow barnacles, mussels, sponges, corals and more. Sometimes it happens even more quickly than that, with seaweed spores taking hold within minutes of immersion, and barnacle larvae settling in within a few hours. Either way, the result is literal drag.
Some estimates suggest that fuel consumption can increase by as much as 6% for every 100 micrometer increase in hull roughness (Source: Shipping and the Environment, 2016). The added weight of all that extra marine wildlife doesn’t help. The added fuel costs coupled with the efforts to combat biofouling costs militaries and marine industries billions.
And then there is the other major problem with marine biofouling: the stowaways.
Marine vessels inadvertently contribute to the global spread of invasive marine species. As often happens with invasive species, they tend to arrive without their natural enemies, such as species that co-evolved with them to keep them in check. As such, they’re able to quickly grow in a new environment, competing with native species for nutrients and real-estate, and generally threatening local ecology. The spread of invasive species through biofouling also places coastal aquaculture at risk. Such was the case in Brittany when the invasive Atlantic slipper snail nearly wiped out local oyster farms.
Biofouling has become such a significant environmental concern that the UN has become involved via its division for Ocean Affairs and Laws of the Sea, in order to foster international collaboration on the matter. Scientifically, its a challenge to track the thousands of stowaway species embarking on free rides around the world, but efforts such as DNA bar-coding approaches to port biosecurity efforts could help keep tabs.
The problem is, by the time the ships reach port, the invasive species are hard to contain, which is why many efforts — including those reaching back to the 1700’s when the British Navy began using copper hulls — are trying to prevent these stowaway microenvironments from forming in the first place.
But that is another very interesting story altogether!