Posted by: barn owl | February 20, 2008

Pollution Pessimism: Plastic Pieces in the Pacific

ResearchBlogging.org
Mr. McGuire: I want to say one word to you. Just one word.
Benjamin: Yes, sir.
Mr. McGuire: Are you listening?
Benjamin: Yes, I am.
Mr. McGuire: Plastics.
Benjamin: Just how do you mean that, sir?

~ from The Graduate (1967)

Whether we live in a G8 nation or a developing country, almost all of us use plastics, which are synthetic carbon-based polymers, on a daily basis. Although the lightweight and durable nature of plastics makes them versatile materials, these same properties allow the wide dispersal of buoyant plastic debris, and the persistence of plastic particles as sediments or as neustonic items (floating near the surface). Ships, recreational and fishing boats, litter on beaches, rivers, and municipal drainage systems all contribute plastic debris to the marine environment. Numerous studies have documented the ingestion of plastic debris by seabirds, fish, sea turtles, manatees, and whales (Derraik, 2002).

How are the amounts of plastic debris and pre-production particles (“nurdles”) in the marine environment measured? Moore and colleagues (2001) used a manta trawl to collect open ocean neustonic samples in the North Pacific central gyre, an area of convergence where debris collects as winds and currents diminish in the center. The authors separated living tissue from plastic particles, and classified the zooplankton in the samples. Tyler sieves, ranging from 4.76 to 0.35 millimeters, were used to sort the plastic particles, and both zooplankton and plastic particles were weighed and counted. The mean abundance for plastic particles in the North Pacific central gyre was 334,271 pieces per square kilometer, with thin plastic films and monofilament or polypropylene line accounting for most of the pieces in the two largest size categories. The mean mass for plastic particles was 5,114 grams per square kilometer, and plastic mass was higher than plankton mass in 6 of 11 samples. Moore et al. (2001) concluded that the large ratio of plastic to plankton in the North Pacific gyre has the potential to affect birds and filter feeders that focus on the surface (photic) portion of the ocean.

bags

My attempt to keep a miniscule amount of plastic out of the ocean and off the landscape = tote bags crocheted from used plastic carrier bags and newspaper wrappers. Each tote is crocheted from yarn “spun” from 60-80 plastic bags.
Photo by barn owl © 2008

A different sampling focus was employed by McDermid and McMullen (2003), to analyze plastic debris in the Hawaiian archipelago (what a perfectly wretched place to do research, eh?). The authors performed beach surveys, both at the high-tide line and at the berm (the level reached by high surf or storm waves), by taking sediment samples; all of the study sites were in remote locations, away from industrial or highly populated areas. Sediment samples were sorted through sieves, and identified as plastic, plant, or “other” (shell, paper, ceramics). Plastics constituted 72% by weight of the debris, with 87% of this being plastic fragments, and 11% pre-production pellets. Small-plastic pieces were most abundant on Cargo Beach, Midway Atoll, with a total of 17,645 pieces. Pre-production plastic pellets were found on beaches distant from industrial areas; sadly, small-plastic debris is likely to be present on every beach in the North Pacific. Importantly, 43% of the plastic pieces in the beach samples are in the 1 to 2.8 mm range, which is the size likely to be ingested by filter-feeding salps and surface-feeding seabirds. This disturbing pollution trend will not disappear anytime soon.

References:

Derraik, J.G.B. (2002). The pollution of the marine environment by plastic debris: a review. Marine Pollution Bulletin 44, 842-852.

Moore, C.J., Moore, S.L., Leecaster, M.K., and Weisberg, S.B. (2001). A comparison of plastic and plankton in the North Pacific central gyre. Marine Pollution Bulletin 42 (12), 1297-1300.

McDermid
, K. (2004). Quantitative analysis of small-plastic debris on beaches in the Hawaiian archipelago. Marine Pollution Bulletin, 48(7-8), 790-794. DOI: 10.1016/j.marpolbul.2003.10.017

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