Microplastics and the deep blue sea

By Dr. Lucy Woodall

Microplastic fibres seen under a microscope.  Lucy Woodall/Natural History Museum  

Microplastic fibres seen under a microscope. Lucy Woodall/Natural History Museum 

“Surely that can’t be natural.”

Those were the words that went through my head when I first saw the strange blue, red, and bright green fibres under my microscope. Recently returned from a scientific expedition on the R.S.S. James Cook, I was back in London, studying deep sea mud collected from the South West Indian Ocean (SWIO). The purpose of the two-month expedition was to assess the biodiversity of seamounts (undersea mountains), and my role was to investigate the diversity of nematode worms that live in the sediment on their slopes.

Instead of microscopic worms, though, I was looking at microplastics, tiny synthetic fibres or particles. When plastic bottles and other garbage are dumped in the ocean, they eventually break down and microplastics are what you get. Studies have shown that these tiny pollutants can have negative physical and chemical impacts on a range of organisms and ecosystems. Already full of chemical additives from the initial manufacturing process, they absorb further organic chemicals and heavy metals once they are in the ocean, thanks to their large surface-area to volume ratio. When microplastics are ingested or otherwise absorbed, these chemicals can and often do accumulate in the tissues of all kinds of animals, causing untold harm as they’re passed along the food web.

First documented in the early 2000s by Prof. Richard Thompson of University of Plymouth (Thompson et. al., 2004), microplastics have been found in many different environments across the globe, from mangroves to Arctic ice. However, one area they had not been documented was in the deep sea, so I set up a collaboration with Prof. Thompson and a number of other researchers to obtain sediment and screen for microplastics from deep-sea locations across the globe.

The R.S.S. James Cook.  P. Boersch-Supan/Natural History Museum

The R.S.S. James Cook. P. Boersch-Supan/Natural History Museum

We recently published our findings in the first-ever report on microplastics in the deep sea (Woodall et. al., 2014). We showed that they are so abundant, the bottom of the ocean could be considered a sink for this pollutant. More research is needed to understand the true impact of microplastics on the environment, but something we can say right now is that these pollutants are so small and the oceans so vast that clean-up is never going to be an option. The first, and best, step is to prevent litter from getting into our oceans in the first place.

I continue to study the impact of microplastics on the deep sea environment at the Natural History Museum in London, while also documenting patterns of litter found on the seabed, and developing methods for working with microplastics.

Dr. Lucy Woodall is a research associate with Project Seahorse and a scientific associate at the Natural History Museum, London. Follow her on Twitter @water_nomad.