World Aquaculture September 2018

26 SEP TEMBER 2018 • WORLD AQUACULTURE • WWW.WA S.ORG P lastics are pervasive, persistent, and perpetual components of the marine environment, and this has been well documented. The impacts of macroplastics (plastic bags, chairs, bottles, and other items) are highly visible, often dramatically, e.g., general pollution, bags smothering coral reefs, choking sea turtles, and starving sea birds. More recently microplastics – the breakdown by-products of macroplastics, components of personal care products, synthetic fibers, and others – have become a major focal point. While microplastics have been a curse of the marine environment for decades, recent publicity and campaign efforts have brought the plight to the forefront and the topic has become the latest scientific bandwagon, driven unfortunately, as are many scientific bandwagons, by the international desire to claim one’s territory in the quest for research funding and notoriety. Scientific research takes time, careful experimentation, and expertise. Far too often, in the rush to publish and stake one’s claimwithin the field, the scientific literature becomes littered with unreliable, dubious and incorrect information. It is entirely irresponsible for scientists and scientific journals to publish questionable data derived from questionable methods. Once published, be it in scientific journals or the internet, it is difficult, if not impossible, for the general reader to distinguish between what is reliable and true versus what is mere hyperbole. And it cannot be unpublished. Much of what is currently available has not been carefully peer-reviewed or vetted and has done nothing more than confuse the entire field. Indeed, one recent supposed review paper included the statement “the literature review process did not include assessment of the reliability of each report” – they simply listed some of the available literature. The methodologies alone for the determination and characterization of microplastics are difficult and expensive and the majority of studies published have not used them. Simple microscopic examination is not sufficient. Experimental protocols used for uptake and depuration studies are severely lacking in scientific rigor or suitable animal husbandry. Microplastic sampling and extraction protocols are inconsistent across studies. The use of muffled glassware, metal equipment and filtered liquid reagents (e.g., Milli-Qwater and ethanol) are necessary for field collection quality control. Studies need to report relevant quality control efforts and eliminate avoidable plastics COMM E N TA R Y The Microplastics and Shellfish Media Frenzy - Stop the Train, We Want to Get Off! Sandra E. Shumway, J. Evan Ward and Kayla Mladinich including collection bottles and ropes. Preservation methods and details like microplastic recovery rates should be reported to determine the validity of the extraction methods used. To extract microplastics efficiently, samples are digested before a density separation. Digestion with hydrogen peroxide has been demonstrated as time-efficient and non-damaging to plastic polymer composition. Alternative digestions using acid, enzymes and alkaline solutions have been used, but little is known about the effect of enzymatic and alkaline digestions on polymer composition. Acids can melt plastics in the sample and therefore should be avoided. Hypersaline sodium chloride solutions or denser salts, like sodium iodide or zinc bromide, are recommended for density separations. Methanol or ethanol can be added secondarily to extract any remaining microplastics. The most important and often most neglected part of the methodology is proper identification of microplastics with Fourier transform infrared spectroscopy (FT-IR) or Raman spectroscopy. Visual sorting with a dissecting microscope can be used for imaging and characterization of the particles’ physical properties, but FT-IR or Raman spectroscopy are needed to validate polymer composition, particularly for particles <500 µm. Many studies claim to have identified microplastics visually but, without spectroscopic analysis, the results are likely biased. The current literature on the presence and impacts of microplastics on marine organisms is seriously flawed. In short, microplastics are difficult to identify and quantify. Many studies have used incorrect or insufficient methodology for identification of microplastics, poor animal husbandry in experiments with shellfish, and some investigators lack any understanding of feeding processes in bivalve molluscs. Microplastics is a sweeping term as it includes particles < 5 mm. This is a very wide spectrum and bivalve molluscs will only be consuming particles in the 1 - 500 µm range, more commonly in the 5 - 150 µm range. It is well-established that filter-feeding shellfish consume microplastics; there is nothing newsworthy there. Indeed, the fact that filter-feeding bivalves consume particles readily and excrete them just as readily made it possible to use them as test particles and markers. We have been using microplastic beads in our research for over 30 years. Microplastics have become the latest scientific bandwagon, driven unfortunately by the international desire to claim one’s territory in the quest for research funding and notoriety. Researchers need to design and carry out experiments using proper and accepted methodologies, read past literature, and not rush to publish prematurely. Sloppy efforts will inevitably cause more harm than good and overcoming bad publicity and stigma is never an easy or even possible task.