Given how diverse marine plastic is, it can also have a variety of effects on marine life. Larger pieces of plastic can become deadly traps – as can be seen in the six-pack rings that can strangle seabirds, or old fishing nets, which sea turtles can get tangled in and ultimately drown. Experts are currently discussing whether marine litter still “only” kills individual animals, or if it might even endanger entire populations.
A recent study shows that today 90 per cent of all seabirds swallow plastic parts; different species are at different levels of risk, depending on their feeding habits. The situation is especially critical for northern fulmars, which spend their entire lives on the open sea and exclusively feed from the water’s surface. Experiments on dead animals have revealed that in some cases, their stomachs are completely full of plastic; many of them must have simply starved to death. As such, it’s highly plausible that plastic litter could decimate fulmar populations in the years to come. What remains unclear is how microplastic particles affect marine animals and ultimately human beings.
Laboratory experiments have shown that different species vary in terms of their vulnerability to the particles. If bivalves are subjected to high concentrations, the particles are transported from the digestive tract into the animals’ cells and tissues, where they can cause inflammations. In contrast, marine isopods appear to have mechanisms in their digestive tracts that prevent microparticles from spreading to other parts of their bodies. And we still have no idea whatsoever whether or not microparticles unwittingly consumed together with seafood pose a threat to human health.