Scientists from the University of Tasmania reported last week that plastic ingestion is having a negative impact on the health of flesh-footed shearwaters, a near-threatened species of seabird. The study found that birds that had eaten plastic had stunted growth and a decline in kidney function. Plastic ingestion kills many species, with more than a million seabirds estimated to be dying from it each year.
A 2017 University of Exeter study showed that hundreds of sea turtles die every year after they become entangled in plastic – items such as lost or discarded fishing nets or holders for six-packs of beer. Last year, Exeter scientists detected microplastics in the guts of every sea turtle species in the Atlantic and Pacific Oceans and the Mediterranean Sea, and also at the nesting sites of loggerhead and green turtles, potentially affecting turtle breeding. As microplastics absorb heat, their presence may raise the nest incubation temperature, skewing the sex ratio towards females.
Toothed whales often accidentally ingest large pieces of plastic while hunting, clogging up their digestive systems. Earlier this year, researchers from a natural history museum in Davao City in the Philippines recovered the body of a Cuvier’s beaked whale that had 40kg of plastic in its stomach and intestines. Scientists in Florida also found plastic bags and a balloon in the stomach of a rough-toothed dolphin calf, which was then euthanised.
Research carried out in 2014 by scientists from the University of Exeter determined that microplastics can enter crabs’ bodies through their gills, as well as by ingestion. Scientists believe this is also the case for other marine creatures, including fish. Entry through the gills increases the chance of the microplastics passing up the food chain to humans.
Plastic pollution also affects marine bacteria, scientists from Macquarie University in Australia reported earlier this year. Tests showed that “exposure to chemicals leaching from plastic pollution interfered with the growth, photosynthesis and oxygen production of Prochlorococcus,” said lead author Dr Sasha Tetu. These photosynthetic bacteria are critical as they produce 10% of the oxygen we breathe.