Microplastics compromise marine worms
Tiny fragments of plastic could pose a serious hazard for sea life. Researchers from the Universities of Exeter and Plymouth found that plastic fragments can reduce the amount of food eaten by an important and common marine creature called the lugworm. Stephanie Wright was one of the researchers and she spoke to Helen Scales.
Stephanie - Basically, we went to collect lugworms from the beach. We also brought them back to the lab with some natural sediment. We wanted to see whether these tiny pieces of plastic, which can be smaller than a grain of sand - these microplastics - could cause any harm at all to important species at the bottom of the food web, which is why we focused on the lugworm. And so, in the lab, we maintained them in sediments, some were exposed to sediment containing different levels of microplastics which overlapped with some environmental levels. And then we kept them in these conditions for about 4 weeks, making observations throughout that time, and at the end, we also quantified their energy reserves as well. What we found is that actually, with very high levels of microplastics, the lugworms reduce their feeding activity. In some levels, which overlapped those reported for the environment, they actually had a lower amount of energy available for important processes such as growth and reproduction.
Helen - So, these microplastics, these tiny fragments of plastics, we do find these in the marine environment. They are out there, aren't they?
Stephanie - That's right, yes. Actually, trends have so far indicated that their abundance in the marine environment is increasing and they can be in the sea surface, in the water column, in the seabed. So, they really are widespread.
Helen - Where do they come from?
Stephanie - They tend to mainly come down from the breakdown of larger plastic items. Everyone knows that plastic litter is an issue for the sea. Scientists have found out this actually breaks down over time into smaller and smaller pieces, into fragments of plastic. We also actually get microplastics purposely manufactured to be of a microscopic size - and that's for products such as skin exfoliators, say for toiletries, toothpaste and also, even clothing. They produce lots of synthetic fibres which come out of your washing machine effluent into the sea. So, it's actually quite a wide range of sources.
Helen - Essentially, these lugworms are almost getting plastic constipation, perhaps. Is it the bulk of plastic inside them that we think is having this effect or could it be something else? Is there something on the plastic that maybe is affecting them chemically?
Stephanie - The plastic we chose to work on we selected because it was free of chemicals. It was free of any additives that could be incorporated during manufacture, because we are interested in the physicality - the presence of that particle itself and what that could do. So essentially, it's taking a broom in the digestive passage. So, in the stomach of these worms, which would normally be a space for nutritional plant matter or sediment grains laden with a vital resource, but what we found is actually this microplastic is taking up space and these worms, they're exerting energy trying to digest them.
Helen - What's the consequences of this study in understanding more about the impacts of microplastics? How does this translate back to the oceans and perhaps ultimately, back to ourselves as well?
Stephanie - This species in fact is very important, it churns the sediment through its feeding activity. So, when you see those casts on the beach, that's a product of it reworking the sediment, like earthworms in soil. So, it's very important to maintaining their health. So, any impacts on it seeding actually, it could have knock-on effects of the animals which live in the sediment. In terms of the wider implications, there are lots of other species that feed in a similar way, that ingest sand and don't show any selections. So, if the plastic is there, they could ingest this, things like sea cucumbers and certain crab species and other worm species. So, there are much wider implications but I think the key thing is, this is at very high levels and we just need to prevent those levels from being reached in the environment so that this doesn't happen.