Saturday, February 2, 2008

Fundamental Properties of Plastic Debris

Ahoy there. It’s Captain Moore giving Anna a break today so that I can chat with you about two fundamental properties of the plastic debris we are finding. I am often asked: What is the size of the Eastern Garbage Patch (EGB) and what type of debris does it contain?

With regard to the size of the debris-impacted area of the North Pacific subtropical gyre, loosely referred to as the Eastern Garbage Patch, I now believe that such a dubious distinction belongs to the whole of the gyre we are surveying. Ocean Surface Current models (OSCURS) by Jim Ingraham show Texas scale areas nicknamed garbage patches in the eastern and western North Pacific where much of the debris resides for decades. We have found that millions of square miles of ocean from 20N to 40N and from 135W to near the international date line, where we have done limited but extensive trawl sampling are significantly impacted, though outside the loose geographical limits of the EGB. In fact, the highest levels yet found by our team have been in the area bounded by 30-33N and 160-170W, an area not considered part of the EGB.

As far as the type of debris we’re finding in this area, an interesting comparison is possible. The Laysan albatross was the first large scale sampler of the plastic plague in the North Pacific.

Its diet of natural debris and squid was supplemented with plastic debris not long after the beginning of the throwaway era. We have dozens of photos of Laysan albatross regurgitated stomach contents taken by Cynthia Vanderlip at Kure Atoll that contain objects you might find at the check out counter of a convenience store, and among the bottle caps, small bottles, cigarette lighters, pens and toothbrushes, are found plastic fragments of various sizes and colors. The manta trawls for zooplankton collection that we have been hauling 700 miles east of Kure Atoll contain a very similar mix. Some identifiable objects, such as a knife sheath, bottle cap, toothbrush, and plastic tub handle which we pulled up in our trawl samples were mixed in with many plastic fragments generated by larger objects that became embrittled over time. An answer to the question: “What kind of plastic do you find in the gyre?”, might be: We find the same kind of plastic that Laysan albatross find. We offer these two pictures for comparison. (The image above is a sample from our manta trawl, below is the image of an albatross carcass containing plastics.)


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