Missing plastic rubbish 'in fish'
Published 30/06/2014 | 20:22
Thousands of tons of plastic rubbish dropped into the oceans is missing - and much of it might be ending up in fish, scientists believe.
A worldwide survey conducted in 2010 showed that the oceans contained between 10,000 and 40,000 tons less plastic than expected.
The lost plastic consisted of small particles between a few microns and a few millimetres in size which was under-represented in the seawater samples collected.
An unknown mechanism must be removing the fragments from surface waters at a rapid rate, say scientists.
One of the most likely possibilities is that the plastic is entering the food web via shrimp-like organisms called zooplankton and the fish that prey on them, and are themselves eaten.
Other research had shown that between 9% and 35% of small fish part way up the food chain contained plastic in their stomachs.
"The most frequent plastic size ingested by fish in all these studies was between 0.5 and 5mm, matching the predominant size of plastic debris where global losses occur in our assessment," said the scientists writing in the journal Proceedings of the National Academy of Sciences.
The team, led by Dr Andres Cozar from the University of Cadiz in Spain, said the nine-month Malaspina circumnavigation analysed data from more than 3,000 sea surface samples collected around the world.
In total, 88% of the sample sites contained plastic debris of varying sizes with the highest concentrations found where large rotating ocean currents converged.
Bacteria breaking down the plastic into undetectable microscopic fragments could also explain the mystery of the vanishing plastic, said the researchers.
"Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the oceans," they wrote.