The study by the University of Tasmania found seabirds eating plastic typically have a higher cholesterol, dissolve less calcium and their wings grow slower than those without plastic
The team studied the plastic intake of shearwater birds (Credit: Twitter, @IMASUTAS)
Eating plastic could be the root cause behind the declining shearwater seabirds population of the Pacific island Lord Howe, located more than one thousand kilometres away from Tasmania, according to a new study.
The research published in the scientific journal Environmental Science and Technology found that ingestion of the material by the animals affects their blood chemistry and physiology – even having a negative impact on the apparently healthy ones.
It was conducted by scientists from University of Tasmania (UTAS), the UK’s Natural History Museum and Lord Howe Island Museum, with the team being led by UTAS’ Institute for Marine and Antarctic Studies (IMAS).
Research scientist at UTAS’ IMAS Dr Jennifer Lavers, the study’s lead researcher, said: “Flesh-footed shearwater populations are declining across the south-west Pacific Ocean and Western Australia’s south coast.”
“Plastic ingestion has been implicated in this decline, but the mechanisms by which it affects shearwaters are poorly understood.
“Our study found that birds which ingested plastic had reduced blood calcium levels, body mass, wing length, and head and bill length.
“The presence of plastic also hurt the birds’ kidney function, causing a higher concentration of uric acid, as well as on their cholesterol and enzymes.”
A closer look at the impact on seabirds of eating plastic
A wide range of research on the effect of plastic consumption by the bird population on Lord Rowe Island has been taking place for more than a decade.
Most of this involves looking at what plastics do to the seabirds’ mortality rate by examining the digestive system of the animals.
During some years of the research, as much as between 80% and 90% of all the chicks studied had at least one piece of plastic in their stomach – in one instance 274 pieces were found in one bird.
The team on the island also found that some of the seabirds that were still alive also had plastic in them, and they wanted to understand the effects this could be having.
They found that some of the chicks with just a single piece of plastic in them weighed less than those without, also observing that the material is making wing growth slower.
The researchers also looked at what impact this ingestion was having on the animal’s blood chemistry.
Dr Alex Bond, the senior curator in charge of birds at the UK’s Natural History Museum who took part in the study, said: “What was interesting was that for certain blood chemistry values we did find some significant effects.
“For example, birds with plastic had higher cholesterol, they had lower dissolved calcium and they also tended to have more uric acid and more amylase in their blood.
“We assumed that there would be some sort of sub lethal effects, but for some of the aspects like cholesterol, we didn’t think that it would just be the presence of plastic that would cause higher cholesterol compared to birds with less plastic.
“Just a piece is enough.”
No specific coloration between the amount of plastic a bird eats and its health, says Dr Lavers
According to Dr Lavers, the data in the research found no specific coloration between the amount a bird eats and its health.
She said: “Our data did not show a significant relationship between the volume of plastic ingested and the health of individuals, suggesting that any plastic ingestion is sufficient to have an impact.
“Until now there has been scant information on the blood composition of seabirds in the wild, many of which have been identified as threatened species.
“Understanding how individual seabirds are affected is also further complicated by the fact they spend little time on land or at breeding colonies, and most mortalities occur at sea where the causes of death are often unknown.
“The complex range of issues that face seabirds – from habitat loss and climate change to fishing and marine pollution – make it vital that we better understand the impact of particular challenges such as plastic debris.”