There are few studies into marine litter that can match the long term character of the over 30-year long monitoring study by IMARES on plastics in stomach contents of Northern Fulmars in the North Sea. However, one other dataset of comparable duration exists: the Sea Education Association from Woods Hole in the USA has a long-term study using surface nets to measure the accumulation of debris in the plastic soup of the North-Atlantic Garbage Patch. Comparison of these two unique datasets in the scientific journal ‘Environmental Pollution’ provides remarkable insights.
Photo top right corner: Preproduction industrial pellets have shown a strong decrease in stomach contents of fulmars as well as in density in the North Atlantic gyre. These granules measure 4 to 5 mm in diameter.
North Sea Fulmars
The North Sea may be considered as one of the source areas for plastic debris in the oceans. Wind and currents make that floating debris is exported to elsewhere. Without constant addition of new waste, the North Sea would clean itself rapidly. The article gives a detailed account on how stomach contents of Fulmars reflect a changing pattern of pollution in the area. In the long run there appear to be no major changes in the overall plastic mass present, but the composition changed significantly. Industrial preproduction pellets have strongly decreased over the years. However, variable quantities of consumer plastics have taken over and have somewhat obscured the underlying patterns.
North Atlantic garbage patch
The densities of plastics in the soup of the North Atlantic garbage patch show remarkably similar trends. Whilst one might expect that continued losses of plastics in source areas would lead to continued accumulation in the centre of oceanic gyres, this cannot be detected in the North Atlantic gyre. Plastic density does not clearly show and increasing trend. Looking at the data in more details, it shows that also her the densities of industrial granules have sharply decreased, just as in the fulmars.
Reduced pollution rapidly visible
The study shows that a reduction of plastic waste in source areas (as for example seen through North Sea Fulmars) is quickly reflected in the large oceanic gyres (reflected in the North Atlantic garbage patch). In short this implies that if we manage to avoid new pollution, that the oceanic garbage patches will rapidly disappear.
This may appear a fantastic message. However, it also shows clearly that the oceanic garbage patches are no more than a temporary reflection of plastic debris in the ocean with apparently very different final destinations. Partly the plastics may sink, or become beachwashed, or the material may crumble to small fragments not reseen, that may or may not undergo true degradation. Animals like seabirds can reduce ingested plastics in their stomachs to invisible small bits before intestinal passage and excretion.
Discrepancy in estimates
A recent study calculated that globally at least 5 million tons of plastic debris enters the oceans from land-based sources. However, the global amount of plastic floating around our seas has been estimated at “only” a quarter million tons, so only about 5% of what is annually added from land-based sources. The strong discrepancy between these figures will remain problematic, but the study published now shows that processes are at work that at least offer some partial explanation.
Avoid further risk?
Unfortunately these findings do not imply a quick solution to the problem of marine plastics. It reflects mainly how little we know about this type of pollution of our oceans and thus of potential consequences for wildlife and man. In that situation the wise approach may be to avoid further risk by stopping losses of plastics into the sea.
- Van Franeker, J.A. & Law, K.L. 2015. Seabirds, gyres and global trends in plastic pollution. Environmental Pollution 203: 89-96.
- This article was published as ‘Open Access’ and is thus freely available through link http://dx.doi.org/10.1016/j.envpol.2015.02.034
- An extended pdf version of the full paper including extensive background information may be downloaded from Seabirds, gyres and global trends in plastic pollution (file size 4 MB)