Microplastic Debris

Microplastics have been isolated from surface water, mid-water, marine sediment, and beach surface in all the world s oceans (Moore, 2003). Majority of the studies have used neuston plankton nets (333 jm mesh size) on surface waters to collect and enumerate samples. Because of the mesh size of nets used, most of the fragments collected are greater than 300 jm in size. Depending on the location, anywhere from less than 10 particles/m to 10 particles/m of seawater has been reported (highest ever count is -lO rn surface). The collection and quantification of microplastics in the ocean has been recently reviewed (Hidalgo-Ruz et al., 2012). 

Isolation of micro- and mesoplastics from debris samples that also include biomass is particularly difficult. Floatation (or density-based separation) alone does not completely isolate the plastic fragments from marine debris. Digestion of sample to solubilize and remove the biomass has been suggested acid digestion (Andrady, 

2011 Claessens et al., 2013), alkaline hydrolysis (Jin et al., 2009), and peroxide digestion (Nuelle et al., 2014) have been used. Recently, proteinase-K digestion was demonstrated to solubilize greater than 91% (wt) of the biomass with no apparent effect on the plastic fraction (Cole et al., 2013). The technique might also be used to isolate ingested microplastics from zooplankton samples as weU. Chemical digestion does not affect most of the common thermoplastics except for some condensation polymers such as polyamides and polyesters. 

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Goldstein, M., Rosenberg, M. and Cheng, L. (2012) Increased Oceanic Microplastic Debris Enhances Oviposition in an Endemic Pelagic Insect , Biology Letters 10.1098 (published online 9 May). 

Using phthalate levels (derived from plastics) in the tissue of larger filter feeding organisms such as whales as indicators of microplastics pollution has been suggested (Fossi et al., 2012). However, plasticized PVC that incorporate phthalates is only a small fraction of the plastics debris sampled at sea. 

However, some data suggest that microbeads, unlike other microplastics, may not significantly accumulate in ocean waters. One recent study examined the data from over 3,000 surface wafer samples collected around the world. Eighty-eight percent of the samples from fhe open ocean contained plastic debris. Microbeads were common in samples from near shore environments but they were negligible in open ocean samples [142]. That finding suggests that the processes that may remove microbeads from surface waters deserve a closer look. 

As microplastics move through the environment they can sorb and transport other contaminants. Plastic debris scooped from the ocean has contained polychlorinated biphenyls (PCBs) at concentrations up to 5 parts per million and dichlorodiphenyltrichloroethane (DDT) at approximately 7 PPM, for example [145-147]. Of particular concern are persistent, bioac-cumulative, and toxic (PBT) compounds that would tend to partition into a plastic matrix due to their hydrophobicity the logical inference is fhaf floaf-ing microplastics could transport PBT compounds through the environment and that perhaps the PBT compounds would enter the food chain as organisms ingested fhe plastic fragments. 

In 2009, research on POPs in the world oceans were studied at an international workshop on the occurrence, effects, and fate of nticroplas-tic debris (University of Washington 2009). The workshop focused on small plastic debris in the oceans, including the amount, location, and environmental impacts of small plastics. Participants presented current research of microplastic occurrence and movement in the oceans, direct effects of micro plastics on marine organisms, interactions of POPs with plastics and the potential for plastics to adsorb and desorb these pollutants in the marine environment and to organisms, and the effect plastics could have on the cycling of POPs. 

Arthur, C., Baker, J. and Bamford, H. (2009) Proceedings of the International Research Workshop on the Occurrence, Effects and Fate of Microplastic Marine Debris. September 9-11, 2008, NOAA Technical Memorandum NOS-OR R30. 

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