The Hitchhiker's Guide to the Ocean

We’ve all heard of spheres like the atmosphere and the biosphere, but a new sphere has been created: The Plastisphere.

(Source: The Longest Swim)

It’s a name used for ecosystems that grow and live on plastic surfaces (left). These ecosystems are mainly microbial and because plastic surfaces are hydrophobic, they can create a thin layer of cells stuck to each other and the surface, known as a biofilm.

Studies on the plastisphere only properly started in 2000 by Dang and Lovell who looked into how biofilms accumulate on plastic surfaces in a marine environment.

Since then we have discovered that due to the much longer half-life of plastic compared to other naturally occurring elements on which biofilms occur (like feathers and wood), the microbes can thrive and be transported long distances.

(Scanning election microscope picture of microbes living on
a piece of plastic. Source: Ocean Portal)

But why is this an issue?

Well these microbes (right) harbour persistent organic pollutants (POPs) – which as we have seen in an earlier post, are naturally occurring in oceans but become harmful when concentrated – and harmful microalgae which, when transported long distances, can become an invasive species, thus a pathogenic danger to marine life not used to these microbes.

Different types of plastics sorb different types of POPs, for example, polypropylene (a thermoplastic found in items like packaging) sorbed higher concentrations of certain POPs than polyvinyl chloride (found in clothes and construction material), so depending on the plastic type floating around the ocean, different pathogens can affect different ecosystems. Zettler et al. (2013) discovered that the main pathogen found on polypropylene was Vibrio which has been attributed to gastrointestinal problems and cholera. A study by Senderovic et al. (2010) found that fish can be vessels for the cholera strain of Vibrio, which could make its way into our bodies.

However, these microbes have been found to be hydrocarbon-degrading and may therefore be a solution to breaking down plastics. Although then we are back to the issue of microplastics all over again, so using these microalgae as biodegraders seems like a nonsensical idea.

It is clear more research needs to be done into the plastisphere, especially its effects through the food chain.