Friday, December 11, 2015

Oceans of microbeads

Ocean of microbeads
Rivers and lakes are not immune to microbead saturation. Studies[i] have shown that major United States water supplies are infected with exfoliating scrubs. The Laurentian Great Lakes, the largest fresh water source in the United States, have been shown to have microbeads in large concentrations up to 400,000 particles per square kilometer. Concentrations are up to one thousand percent higher near population centers. These plastics particulates are microbeads from cosmetics and they make up 81% of all particulates collected from the surface waters. From our rivers, these beads flow to the sea.
Beads made from various materials drift through the layers of our oceans[ii]. Lighter density beads float on the ocean’s surface where they join with plankton blooms. Denser beads drift deeper and into the sediment layers. The beads can drift between these layers by developing surface fouling[iii], a scum or slime of various types that form around and within the bead pores. This process that attracts other micro particles which then develops into an algae mats. This algae mat become host to invertebrates and the microbeads become an ecosystem of their own. These microbead colonies join the naturally occurring micro-particulates of the ocean. Their drifting multicolored beads like cake sprinkles in the salad bar of the ocean food cycle.
                There are no clear models for where ocean plastics end up in their journey, but one form of microbead sink is Artic Ice. Researchers studying Artic ice shelves found 38 to 234 particles of plastic per cubic meter[iv]. This age old method of scrubbing the ocean is changing its patterns and recent melting trends could lead to a release of over a trillion stored plastic particulates[v]. These particulates are looking at a long life time drifting in our marine environment.
While plastics on the surface break down at a steady rate, microbeads in the water are shown to decay at a significantly decreased speed[vi]. Under ideal circumstances oceanic microbeads break down at a rate of 5.7% per ten years[vii]. The actual rates expected rate is closer to 1.7% every ten years. This is due to floating plastic’s tendency to develop surface fouling. These plastics are in it for the long run, taking roughly 110 years for the beads to break down to 50% of their normal size.
That’s a long trip for anyone, but at least these beads aren’t toxic, right? Wrong. Microbeads absorb nearby toxins, such as pesticides. Microbeads have unique features that make them different from the micro-particles of the ocean. Their oil based surfaces are pocketed with fissures that allow for Velcro like connections to form between the beads and toxic substances. These substances are attracted by their natural tendency to be hydrophobic, which leads them to microbeads like a moth to a flame. Water containing microbeads is found to have levels of toxicity 104 to 105[viii] times higher than natural ocean water.
                We’ll be looking deeper into the food web in the next post, to see who’s eating these little toxic plastic nuggets and what that does to them.



[i]   Eriksen, M., Mason, S., Wilson, S., Box, C., Zellers, A., Edwards, W., Farley, H. & Amato, S. (2013). Microplastic pollution in the surface waters of the Laurentian Great Lakes. Marine Pollution Bulletin 77, 177-182.
[ii]  Hidalgo-Ruz, V., Gutow, L., Thompson, R. C., and Thiel, M. (2011). Microplastics in the marine environment: A review of the methods used for identification and quantification. Environmental Science &Technology 46, 3060-3075. doi:10.1021/es2031505
[iii]  Andrady, A. L. (2011). Microplastics in the marine environment. Marine Pollution Bulletin 62, 1596-1605. doi:10.1016/j.marpolbul2011.05.030
[iv]  Obbard, R. W., Sadri, S., Wong, Y. Q., Khitun, A. A., Baker, I., & Tompson, R. C. (2014). Global warming releases microplastic legacy frozen in Artic Sea ice. Earth’s Future 2, 315-320. doi:10.1002/2014EF000240
[v] Obbard, R. W., Sadri, S., Wong, Y. Q., Khitun, A. A., Baker, I., & Tompson, R. C. (2014). Global warming releases microplastic legacy frozen in Artic Sea ice. Earth’s Future 2, 315-320. doi:10.1002/2014EF000240
[vi] Andrady, A. L. (2011). Microplastics in the marine environment. Marine Pollution Bulletin 62, 1596-1605. doi:10.1016/j.marpolbul2011.05.030
[vii] Andrady, A. L. (2011). Microplastics in the marine environment. Marine Pollution Bulletin 62, 1596-1605. doi:10.1016/j.marpolbul2011.05.030
[viii] Mato, Y., Isobe, T., Takada, H., Kanehiro, H., Ohtake, C., & Kaminuma, T. (2001). Plastic resin pellets as a transport medium from toxic chemicals in the marine environment. Environmental Science &Technology 35, 318-324.

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