Charles Moore. The way this information was presented in the media, you'd think it was possible to walk for miles across the ocean on a carpet of flotsam and jetsam. Its existence had been predicted 10 years earlier by NOAA. Well it turned out that this was one of those things that we know for sure which just ain't so. Because a team of Spaniards went and obtained some data which (pffffff!) let some air out of that hypothesis.
The Spanish government funded Expedición Malaspina (2010-2011) which sent two ships Hespérides and Sarmiento de Gamboa off in the tracks of Ale[ss|x|j]andro Malaspina [another Shakepelinge issues here] who went exploring round the world between 1786 and 1794. The 2010-2011 expedition generated scads of data about all sorts of maritime questions but their sexiest finding is that we cannot account for 99% of the plastic garbage that we believe to be in the oceans. It was written up and published in PNAS a month ago. We have a pretty good (within an order of magnitude) idea of how much plastic is manufactured each year and it is widely accepted that 0.1% of it finished up getting washed out to sea or dumped there directly by large continually consuming ships like the QEII or the aircraft carrier USS Nimitz with a crew of more than 5000 all quaffing coke and sprite like they were back home in New Jersey. That all amounts to a guesstimate of 1 million tons of long-lived crud. But the Malaspinistas trawled through the gyres and other parts of the ocean and found levels of only 500g/km^2 which is a long way from being a light dusting let alone solid islands of matter. Where is the missing tonnage? The Malaspinistas offer a few hypotheses:
- There are, as yet unclassified, bacteria that can feast on styrofoam PVC and PTFE
- The UV-chemical breakdown is more efficient than previously thought and all the plastic is in nano-particles (and hence very trendy!) smaller than 0.2mm which is the mesh-size on the Malaspina trawls
- The plastic may be incorporated in the silica and calcium carbonate shells of small marine organisms like diatoms and foraminifera which die and sink below the trawl depth.
- They are treated as food by mesopelagic (200m-1000m deep) fish like filter feeding lantern-fish (Myctophidae) of which there are 250 known species ranging in size from 20-300mm.
Everything else: seals, skuas, dolphins, whales, squid, penguins, tuna, sharks, eats the mesopelagic chaps either directly or concentrated by some intermediate predator. The current working model therefore is that 50 years worth of plastic has been broken down into particles smaller than 4mm, consumed by the mesopelagic fish in a rather indiscriminate feeding frenzy, and are are now working their way up the food chain. There are adult whales tooling around the world today which were born before we started to foul their living quarters 50 years ago. Again, notwithstanding the National Geographic pictures of dead seabirds full of plastic detritus and a quantitative study that found 65% of 171 birds had at least one piece of plastic in their guts [whoop whoop small sample-size alert] the impact may still lie in the future. They reckon there are 600 million tons of mesopelagic fish and they may be able to tolerate a 1% burden of plastic in their diet.
Conclusiom (for now): There may be a huge plastic sink in the large marine mammals that have managed to survive the onslaughts of Norwegian and Japanese 'scientific' whaling, and aren't dead yet from blockage of their guts by indigestible fragments of plastic. Clearly lots of scope for critical evaluation of the assumptions, the extrapolations, the data, the conclusions of this study but me quito el sombrero to the Spanish team for going out a getting some original data.