Scientists are discovering that water pollution is worse than we think. There are microscopic pieces of plastic that exist in the ocean at concentrations up to 400,000 in the top .5m of the surface of the ocean called microplastics. The microplastics focused on in this study are plastic particles smaller than 5 mm in length that enter the marine environment. Microplastics are very dangerous and can cause many environmental issues when they are ingested by marine organisms and carry pollution into the water.
The new procedure scientists are using to collect the concentration of microplastics is called the “multi-level trawl” (MLT) method. The MLT method is a series of 47 tows dragging the MLT .5 meters at a depth of 5 m; making the duration of each tow between 52 and 66 minutes. After the tow, the sample content is frozen and shipped to a lab to be processed. The collected content is separated into two different size classes, one of particles smaller than 5mm and one of particles bigger than 5mm. The smaller particles were disregarded; so once the scientists separated out the larger particles they counted about 30,000 microplastics from one sample. This new process takes depth into account, and it showed a 40% increase in microplastic numbers from previous studies, which only observed microplastics at the surface of the water.
What does this mean?
They concluded that microplastic concentration decreases with depth in this study (the concentrations in the top two nets being 9 times greater than the lower nets). While the numerical concentrations of the smaller particles were greater, the mass concentration of the actual 5mm microplastics surpassed the smaller particles; therefore posing a greater threat to the environment.
The cons of this study include the fact that mesh size does affect the results. The concentration of microplastics increase with smaller mesh, and other studies found that numbers can be increased by 100,000 times. Scientists need to find a way to universally measure the concentration of microplastics possibly through either extremely dense mesh or a uniform size of mesh.
Finally, these scientists project that the concentration of microplastics will be 10 times greater by 2025. In order to properly understand the impact of this pollution we still need to develop more effective ways to sample and calculate these microplastics and their concentrations. Scientists also should start taking into account smaller plastics and ones of varying shape as well as furthering the use of MLT’s. As we begin further grasp an understanding of microplastics, we need to figure out ways to minimize our impact as humans on the ocean and to decrease, if not stop, these numbers from growing over time.
Lauren Shelby ’19
Kooi, Merel, Julia Reisser, Boyan Slat, Francesco F. Ferrari, Moritz S. Schmid, Serena Cunsolo, Roberto Brambini, Kimberly Noble, Lys-Anne Sirks, Theo E. W. Linders, Rosanna I. Schoeneich-Argent, and Albert A. Koelmans. “The Effect of Particle Properties on the Depth Profile of Buoyant Plastics in the Ocean.” Scientific Reports 6.1 (2016): 1-10. Nature. Web. 15 May 2017.