Life in Plastic, It's Not Fantastic
Raman spectroscopy highlights the presence of an invisible pest lurking below the ocean’s surface- microplastics.
Matthew Hallam | | Quick Read
You’d have to live under a rock to be ignorant of the plastic pollution problem. Though the first evidence for plastic debris in the Atlantic and Pacific oceans surfaced in the 1970s, studies of deep pelagic waters – which provide the largest volume of space for inhabitation of all environments on Earth – have been lacking, leaving us with a shallow understanding of the issue.
Anela Choy and colleagues set out to change that. The team modified the filtration equipment on a remotely operated deep-diving vehicle to collect microplastic measurements using Raman spectroscopy (1) – despite many challenges; for example, Kyle Van Houtan notes the likely reason for differences between sample and reference spectra: “The reference library used near-pristine industrial samples, while samples had been subjected to wind, waves, sun, biofouling and potentially repeated digestion by marine species.”
A second library of Raman spectra was curated based on degraded fishing gear of known materials, and statistical differences between the two spectra were used to calibrate microplastic analyses. Using microscopy with Raman, samples from depths of 0-1000m and from biological samples (pelagic red crabs and giant larvacean sinkers – chosen for their particle feeding habits) in Monterey Bay were identified, quantified and assigned to 13 plastic polymers commonly identified in environmental studies.
Microplastics were identified at all depths – with the highest concentration (15 particles per m2) observed 200m below the surface – and across all biological samples studied. The results shocked the researchers; “There are higher concentrations of plastic at depth in Monterey Bay – a success story of ocean protection – than have been reported at the surface of what’s perceived to be one of the dirtiest places in the ocean: the Great Pacific Garbage Patch,” says Van Houtan. Polyethylene terephthalate was the most common plastic in all instances, followed by polyamide, polycarbonate and polyvinylchloride.
Having established the presence of microplastics in marine species capable of transporting them into food webs and to the ocean bed, lead investigator Choy says that she is keen to examine whether some microplastics are more readily transferred through marine food webs than others. Such an understanding of plastic distribution mechanisms in marine ecosystems could provide crucial information for identifying sources of pollution, informing policy, and supporting conservation.
We can all play our part in protecting the environment at home – or in the lab – so please don’t forget to reduce, reuse and recycle (where possible).
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- CA Choy et al., “The vertical distribution and biological transport of marine microplastics across the epipelagic and mesopelagic water column”, Sci Rep, 9 (2019).