14 pieces of plastic. That is the median lethal dose (LD50) required to be ingested to kill 50% of the whole turtle population.
Turtles are not all small creatures. The largest individual being a female leatherback that washed ashore in Anglesey, North Wales in 1988, weighing 900kg and measuring 2.75 meters.
And yet, just 14 pieces of plastic would be enough to kill this phenomenal animal.
In fact, this 900kg female leatherback was found dead, not due to ingesting plastics but to drowning after getting tangled up in discarded fishing lines, commonly known as ‘ghost gear’.
640,000 tons of ghost gear is lost in the ocean every year. This affects all marine life as first algae may begin to grow on it, attracting small fish which become entangled, attracting larger predators which also become entangled and so on until there is enough weight to cause the raft to sink to the seafloor where the organisms decompose. Once decayed, the ghost gear then rises, and the cycle begins again. In 2014, it was estimated that 15,000 turtles have been killed by ghost nets just in Australian waters.
In Australia, they necropsied as many turtles from around the coastline. From the 246 necropsied turtles and the 706 necropsied records it was determined that the LD50 of plastic for turtles was 14 pieces. This is due to inflammation in the gut causing a gas build up in the stomach and intestines which can sometimes rip through the stomach so there is gas inside the body of the turtle. This causes the turtle to be unable to dive for food and they are more likely to be subject to boat-strike, if they don’t starve or die from the ingestion of the plastic itself.
30% of necropsied turtles in Australia had plastic within their bodies.
50% of turtles worldwide had plastic within their bodies.
Australia also surveyed the entire 66,530km of coastline to work out where the plastic was coming from and 90% was local.
This research has led to scientists attempting to source where the rest of rubbish comes from to decrease global inputs while cleanups are carried out on local scales. This can be done by using the past 20 years of ocean currents data to specifically map where rubbish is being released from.
By working out how much is washing up over a set period, it can be determined how much of each type of plastic is still in the ocean and therefore, how much is left to clean up.
My Future
When listening to this talk at the British Chelonia Group Northern Symposium, I was simply shocked by the statistics shown. We are always bombarded by ‘plastics are bad’, ‘save the turtles’ and ‘don’t use a straw’ but the overall message of the scale of the problem faced seems to be lost.
After hearing this, I felt moved by the scale of the problem our oceans face. I wanted to make a difference and have since considered moving away from a career working directly with animals and more towards the clean up and maintenance of animals habitats to ensure that these animals have a place to live in the future.
This talk has enable me to think in further detail about the care and maintanance of habitats as opposed to simply keeping the organism itself safe from harm.
If you enjoyed today’s post please make sure to like and subscribe.
Zoology Composed 