Research on marine plastics is revealing its spread up the food chain

Happy New Year to all our followers! This year we’re going to try something new on Naturally Speaking – we’re going to be blogging. Our ‘Researcher Round Table’ podcasts will continue, but to keep you updated with a broader range of content, we’re also introducing guest blog posts from researchers at all career stages from across our Institute.

Some will be posts about recent papers that are broken down to tell the bigger story and from the personal perspective of the author; others will be more about the process of doing the research—be it weathering storms in coastal Scotland while surveying seabirds, negotiating forests in S. America or (wildebeest) ‘tails’ from the field in the Serengeti. We’ve got it all. First up is 3rd year PhD student Sjúrður Hammer (@sjurdur) to tell us about the worrying spread of marine plastic.

Categorizing plastic found in seabirds
Categorizing plastic found in seabirds. © Sjúrður Hammer

Research on marine plastics is revealing its spread up the food chain

The environmentalist Bill McKibben once said that “we live in a post-natural world” with respect to the unprecedented impact we humans are having on the planet through greenhouse gas emission. But another impact of human activity that is almost equally worrying is the spread of waste plastic in our oceans. Recent estimates indicate that there are around five trillion plastic pieces floating in our oceans, and this may be an underestimate. Scientists are still unsure where such plastic ends up, and so we have yet to fully realise the scale of the issue.

A few years ago a regional monitoring scheme called Save the North Sea (SNS) set out to quantitatively and qualitatively assess the amount of plastic in the North Sea. Seabirds provide an important indicator of ocean health. Groups such as the tubenoses (Procellariiformes), which include fulmars (Fulmarus glacialis) and albatrosses, feed on floating prey from the sea surface and thus are particularly prone to accidentally picking up floating plastic particles. The fulmar was therefore a natural choice for the SNS monitoring scheme, because they are known to accumulate marine plastic, and they are distributed throughout the North Sea and North Atlantic.

The SNS also needed a reference sample from a relatively pristine area outside the North Sea, and for this they selected the Faroe Islands. What they found here was worrying – fulmars around the Faroes also contained a significant amount of plastic fragments. While the plastic load in these fulmars was five-fold less than the amount found in fulmars in the North Sea, it demonstrates quite well that the range of marine plastic is much further than previously thought.

My first personal encounter with marine plastic waste came as a great surprise during my last fieldseason on Skúvoy, Faroe Islands, where I study a seabird called the great skua (Stercorarius skua).

Sjurdur with great skua © Sjúrður Hammer
Sjurdur with great skua © Sjúrður Hammer

We explore skua diet by investigating their regurgitated pellets, which contain indigestible materials of whatever they have eaten, and provide a reasonably good idea of what’s been on the menu.

To my surprise I have found several pellets that contain plastic particles. I say surprise, because although great skuas are not known to be particularly picky with what they eat, they generally don’t feed on the ocean surface; they prefer instead to scavenge from fishing boats, steal from other birds and even kill and eat other seabirds such as fulmars, puffins and kittiwakes.

While it is impossible to establish the origin of the plastics in skua pellets at this point, it appears likely that they’re from secondary consumption of plastic particles, i.e. those eaten by fulmars or other seabirds, which have then fallen prey to the great skuas.

Plastic fragments found in great skua © Sjúrður Hammer
Plastic fragments found in great skua © Sjúrður Hammer

To my knowledge, this is the first observation of plastic found in the diet of the North Atlantic great skuas. We know that marine plastic is found in the ocean and seabirds around the Faroes, but for this plastic to penetrate so high up in the food chain is unique and may provide new monitoring tools in the future.

There are many uncertainties regarding the implications of finding plastic in great skuas. For example, we don’t know how long the plastic remains in the birds, so we don’t yet know if it will accumulate over the years as we have seen in other seabirds. A further concern is the propensity for plastics on the ocean surface to act as magnets to hydrophobic (oily) pollutants; an increasing amount of research is finding correlations between plastic consumption and increased concentrations of such pollutants.

While plastic in top predators such as great skuas may not be necessarily detrimental to their health, at least directly, we can appreciate that predators such as gulls and skuas may represent a new pathway of marine plastic into new ecosystems; but the long-term effects of exposure to marine plastic are still largely unknown. In a case of bad karma, the plastic we cast out into the ocean is finding its way back on shore, and high up in the food chain.

Additional reading:

Contact Sjúrður Hammer:@sjurdur

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