The visible effects of plastic entering the ocean are sadly all too clear to us now, but what about the plastic we can’t see?
Microplastics, plastic fibres and fragments that are between 1 mm and 0.001 mm, account for a significant proportion of ocean plastics. The NOC’s microplastics team carries out cutting-edge research on the distribution and transport of plastics to and within the ocean, to better understand what happens to this plastic, and effects on marine life.
For plastic-free July, we spoke to the NOC’s Dr Mike Clare, Principal Researcher in Marine Geohazards and Sedimentology, about what it’s like to work in the NOC’s microplastics team, and his exciting brand-new research. Meet our full microplastics team.
What is your role within the Microplastics team at the NOC?
My role is to determine the pathways of microplastics into and across the ocean, to discover their ultimate resting place in the deep sea. Much of my research has focused on understanding powerful avalanches in underwater canyons, which transport huge quantities of sediment to the deep sea. As well as sediment, such as sand and mud, we have discovered that these powerful flows can also transport other materials, including organic carbon that provides food for important deep-sea ecosystems, but also large quantities of pollutants, including plastics.
With international collaborators, including Ian Kane at Manchester University, I have been investigating how these flows, and other types of seafloor currents, act like conveyor belts for microplastics, transporting them vast distances across the deep seafloor. These seafloor currents locally concentrate microplastics in the deep sea, in a similar manner to surface currents on the ocean surface, creating pollution hotspots that are unfortunately often where deep-sea life congregates.
What drew you to working in this area?
Surface currents can locally concentrate floating plastics on the top of the ocean, trapping them within sub-tropical gyres, and creating the now infamous floating 'garbage patches' widely covered in the media. However, most ocean plastic is heavier than water, and these floating surface accumulations account for only 1% of the plastic that has entered the ocean (as highlighted in the recent NOC plastics report). So where is the missing 99%? It is this question that got me interested, because my research focuses on tracking the fate of particles from land to the deep sea.
I use techniques based on studying natural sediments to determine the pathways and fate of pollutants in the ocean. Our sampling of seafloor sediments far from land in the western Mediterranean Sea revealed the highest concentration of microplastics yet reported anywhere. We linked these high concentrations to a vast network of seafloor currents, and explain where and why these microplastics hotspots are concentrated.
What science are you currently working on in relation to microplastics?
I am working on several projects that investigate how different types of seafloor currents disperse or concentrate microplastics. In particular, I am interested in how microplastics are transported along underwater canyons, some of which are far larger than the Grand Canyon. Many connect directly to large rivers and may effectively funnel pollution from land to the deep sea, but most lie 100s of km from shore so they were not expected to be polluted. However, recent work as part of the large NERC CLASS programme has shown that even these land-detached canyons can feature high concentrations of litter (mostly from fishing) and that vigorous seabed flows may be responsible for transporting litter into the deep. Work is underway to determine how significant these flows are for transporting microplastics and whether we have underestimated the role of these land-detached canyons in funnelling pollutants into the deep ocean.
I also work on understanding the often-weird behaviour of microplastics in the ocean. While we hoped to translate our understanding of sediment grains, we soon realised that microplastics often behave in a different manner to naturally-occurring particles - due to their density, shape, how they degrade and interact with other materials . If we want to know where microplastics end up, we need to understand this complexity, which requires laboratory experiments, water and seafloor sampling, and direct monitoring of multiple processes at field-scale. This requires international collaborations and seagoing expeditions, which the NOC is well placed to lead.
What is your favourite thing about the work you do?
I am consistently amazed by the vast network of seafloor currents that traverse the global ocean and the power of underwater avalanches that can travel over 1000s of km. Until recently, we have only been able to witness these events at laboratory-scale or through simulated models. Novel technology, including that developed at the NOC, now allows us to directly observe these processes. These new measurements are changing the way we understand pollution transport, and also the complexity of the ocean in general. It is a really exciting time to study the ocean.
What impact does your science have on society?
Shocking images of the so-called surface garbage patches have been a stark wake-up call about plastic pollution in the ocean. However, most of ocean plastic lies unseen, far below the surface and is less obvious to most people. In part, the work of the microplastics research group is to highlight this issue so it is not ignored and understand whether we should be concerned.
Our research aims to understand how, why and where plastic ends up in the ocean and to what degree sensitive habitats and organisms are exposed to it. Even if we switch off the sources of plastic to the ocean today, we will be left with a decades-long legacy of waste mismanagement, but we can make informed decisions about waste management if we can track it back to its source, which is another aim of our research.
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