The effect of plastics on our environment and wildlife is almost beyond the scope of our imagination, and scientists are just beginning to uncover the scale of the problem spread through the food webs of the marine environment.
Recent research has revealed that tiny fragments of plastic sink into sand and mud on the seafloor where they are eaten by many of the small creatures living there as they feed. These have a key role in coastal ecosystems, as an important food source for other creatures, including the many bird species found around our coast.
It's been discovered that worms, like the lugworm and ragworm found on our shores, feeding in highly contaminated sediments will eat less, thus gaining less weight, and have less energy for growth and reproduction. This could have a significant knock-on effect for many of the birds that depend on them as a key part of their diet, particularly if the populations of worms were to decline.
Marine worms also provide a vital ecosystem service, much like earthworms, burrowing through the mud, mixing in nutrients and introducing oxygen, that supports the survival of other small invertebrate species.
Other studies have shown that ingesting microplastics can transfer pollutants into worms. Microplastics have been shown to concentrate chemicals, like pesticides and detergents, onto their surface. Many of these chemicals are environmentally persistent, and can accumulate in the tissue of the organisms consuming them. As an abundant prey species, marine worms could pass these through the food chain to top predators, like many of the birds we see around the shore.
All of this happens at a tiny scale, underwater, often within the sediment itself. The birds we see out on the mudflats, returning year after year, are the visible part of a complex system of interactions that happens in these environments, the flagships for a whole series of ecological processes.
It is important that we aim to prevent the build-up of plastic and microplastic debris in the marine environment. Better waste handling and making smarter choices in the materials we use as small, simple steps we can all take.
By Vicky Inglis