Plastic collected from remote corners of the South Pacific Ocean, including the nesting grounds of New Zealand albatrosses, has confirmed the global threat of plastic pollution to seabirds.
In the findings published in the journal Aquatic Conservation: Marine and Freshwater Ecosystems, the researchers looked at plastic collected in far corners of the South Pacific Ocean, including the nesting grounds of New Zealand albatrosses.
The results showed that albatrosses are more likely to eat brightly coloured plastic, particularly red, green and blue, likely mistaking it for prey. The study suggests that brightly coloured fishing gear from commercial fishing operations around these islands could be the source of some of the plastic found in the nests.
In the case of diving seabirds such as the Sooty Shearwater, the plastics found in their stomachs were mostly round white/grey hard plastic items. The researchers believe that most of these objects are accidentally ingested when the birds eat fish or other prey that have consumed plastic.
“One of the interesting takeaways from this study is that it shows how far plastic can travel in the ocean. Some of the areas where we collected the plastic are very remote. To me, that shows that it's a global problem; It is not something that a single country can solve on its own”, emphasizes Christopher Robertson, co-author of the study.
Seabird will affect most seabird by 2050
By evaluating the patterns of interactions between seabirds and plastic on a larger scale, that is, throughout the South Pacific Ocean, the team, led by the study's lead author, Valeria Hidalgo-Ruz, from the Millennium Nucleus Center in Chile, confirmed that even seabirds in one of the most remote areas in the world, the Rapa Nui (Easter Island) ecoregion, are heavily affected by this global problem, “highlighting the need for urgent solutions,” says Hidalgo-Ruz.
The ingestion of marine plastics is a major problem for seabird conservation and will affect most seabird species by 2050, according to estimates.
Where does the plastic come from?
Plastic is a ubiquitous material that we all use. Much of it is only used once and then thrown away. You may come into contact with single-use plastics more than you think.
It takes the form of discarded single-use packaging, such as plastic straws and cups. These are containers for household items, such as shampoo and cleaning products. It can even be clothed. Synthetic materials, such as polyester and nylon, shed microplastics when washed.
Why do seabirds eat plastic?
Every year, hundreds of thousands of seabirds ingest plastic. It is estimated that one million birds die from plastic each year. This problem has grown explosively.
In the 1960s, less than 5% of birds had plastic in their stomachs. Twenty years later, more than 80% of birds had plastic in their stomachs. It is projected that by 2050, 99% of seabird species will ingest plastic.
Plastic ingestion also affects juveniles that are too young to hunt alone. Adult birds return to nests with plastic that they mistake for food. Chicks ingest the plastic and are less likely to survive to adulthood.
Plastic reduces the volume of the stomach, which often leads to starvation. Dead seabirds are often found with stomachs full of plastic debris.
Seabirds mistake plastic debris for prey. Some birds, such as albatrosses, eat fish eggs which they deposit on floating debris. When the albatrosses eat the eggs, they also consume plastic.
Colour matters
For the study, the researchers compared these items to similar plastics found elsewhere in the Pacific. They analyzed the types of plastic, including its colour, shape and density.
They found that albatrosses are more likely to feed on red, green, blue and other brightly coloured plastics because they likely mistake them for prey. The researchers suggest that commercial fishing gear could be the source of some of the plastic found at nesting sites.
Diving seabirds like the black shearwater (Ardenna grisea) mainly had round, white and gray hard plastic on their stomachs. The researchers believe the birds accidentally swallowed these plastics when they ate fish or other prey that had first ingested the plastics.
Toxins in the body
The most serious effect of plastics is the ingestion of waste that, due to accumulation in the stomach, can end up obstructing the digestive tract, even causing the death of the animal due to starvation or suffocation.
Second, plastics can cause waste to break down in the stomach and contribute toxins to the body, or affect the health and physiology of birds. And thirdly, entanglements and snags with nets, hooks and other parts of fishing gear or even with floating garbage of terrestrial origin.
Plastic ingestion has been dramatically documented in populations of Laysan albatross (Phoebastria immutabilis), a species native to Hawaii. In this area is one of the gyres where ocean currents concentrate a large amount of waste.
In theory, adult albatrosses could overcome this obstacle, since they are capable of excreting waste through their mouths. But the problem occurs when they feed the chickens, which accumulate all the plastic that their parents bring them.
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