An advantage of plastic: it is durable. A disadvantage of plastic: it is durable.
The durability of plastics causes plastics to build up in the ocean, which has become a global concern. Due to its pervasive nature it does not decompose but breaks down slowly into smaller pieces, microplastics. It is widely known that plastic pollution poses many threats to wildlife. Photos of entangled seals, turtles with plastic straws in their nose, and birds and whales with stomachs full of plastics have been floating on social media for years. Ingestion of plastics has been documented across all trophic levels. Seabirds are particularly at risk, as plastics accumulate on the ocean surface, where the seabirds feed. First reports of seabirds ingesting plastics come from the late 60s. The birds can ingest plastics by mistaking it for food prey or ingesting prey that had ingested plastic, which leads to biomagnification along the food chain. Studies agree that plastic pollution is widespread in marine and terrestrial ecosystems, but the extent of the impact on wildlife is not yet fully understood.
The area of Skálanes, where we stayed, provides habitat for a wide range of wildlife, including many seabird species. Arctic terns in Skálanes now make up one of the biggest colonies in Iceland, however, in the past the colony had lower breeding success due to unknown factors. They have the longest migration route in the animal kingdom, travelling between the poles twice a year. This means that their diet primarily consists of marine small fish like sand eels, which are likely to be affected by plastics themselves.
My project’s aim was to investigate the extent of the plastic pollution in the remote area of Skálanes. Firstly, we did a beach clean in the area to map out the extent of plastic pollution and to see its sources. In a few hours, we collected so much plastic debris to fill up 6 large bin bags making up almost 500 pieces. The majority of plastics originated from the fishing industry (pieces of ropes and buoys) and food packaging (styrofoam, bottles and lids).
Secondly, I collected samples of sediment from the beaches and analysed them in the lab for microplastics. My plan was to use simple analysis method of density separation. Plastics have considerably low density, so concentrated saline solution separates pieces of plastic from the sediment and they float at the surface. The solution is then poured through a cascade of sieves to catch any plastics, which were then analysed under a microscope. However, as it turned out it was not so easy. I had to improvise and use the apparatus available in the newly established lab to avoid complicated transport of samples back to Glasgow.
Microplastics, which are more likely to be ingested, can contain high amounts of persistent organic pollutants (POPs). POPs can enter the body and alter the hormone levels affecting the animals’ reproductive success. Hence, another aim of the project was to see if the plastics present in the environment were ingested by the local fauna, in particular, the terns. I was working with Agate measuring and weighing the tern chicks in the colony. The birds did not particularly enjoy when we were handling them so they defended themselves by giving me a sample of their excrement. Analysing faeces is one of the best non-invasive ways of determining microplastics ingestion. The lab analysis was done in the same way as with the sediment. I was hoping to link the ingestion of plastics to the breeding success, however, that was too ambitious and would need further research. In addition, every now and then we found a dead adult tern. Since it died of natural causes, we dissected it to see if there were any plastics present in its digestive tract. Fortunately, we did not find anything that would be related to human activity. More likely the cause of deaths was starvation, as many of them had an empty stomach.
According to my research, the plastic is present in the environment, but has not affected the Arctic terns yet. However, previous studies showed that other seabirds on the same trophic level ingest plastics. In the future, I would be curious to look into what factors determine why plastics are found in some species and not others.