How Can Microplastics Harm Marine Life?

Most studies concerning the harm of microplastics towards health and impediments to biological processes examine marine animals most thoroughly. In a North Carolina Coastal Federation forum on microplastic pollution, executive director of the POP stated that "over 300,000 marine mammals each year" are affected by plastic pollution. Given that marine organisms eventually make their way up the food chain, and the fact that some of these species have similar biological makeup and functional characteristics of humans, it is no wonder scientists are exerting so much energy into the analysis of these particles in aquatic organisms.

ScienceDirect features a research paper discussing the effects of trace elements adsorbing to microplastics, and how this may lead to increased toxicity and transmission of harmful chemicals throughout our environment. In one study, zebrafish, a freshwater species, were found to have ingested and accumulated plastics under five microns in their “gills, liver and gut after 7 days exposure.” In other instances it has been seen that the accumulation of PCBs from ingested plastics have been identified in certain aquatic organisms (scientists have noted that there is still not substantial evidence on negative health effects due to this intake). The death of many of these fish have been linked to complications in their metabolic processes, disruption of endocrine processes, increased buildup of lipids in their livers, and inflammation from the accumulation of these plastics and the various substances adsorbed to them. This is just one of many cases in which aquatic organisms are extremely put at risk due to microplastic pollution. Not only that, but disrupted light and food distribution have also been identified as hinderants to the natural functions of aquatic ecosystems. Health effects and impediments to natural ecosystems as dire as these prompt scientists to wonder whether we may face similar health implications as a result of ingesting microplastics on a daily basis.

Sea birds are especially at risk of plastic pollution through direct ingestion of plastic material and indirect digestion by bioaccumulation up the trophic levels. With 44% of marine birds having ingested plastics, according to researcher Lauren Bradley and coworkers, these birds are susceptible to medical complications directly from plastic particulates and the increased adherence of harmful pollutants (i.e, metal debris) which can lead to the fatality of these birds. With greater accumulation of plastic particles in their GI tract and stomach, the likelihood of starvation or obstruction of their intestines increases significantly.

Published in Nature, a recent discovery by Mexican researchers shows that macroplastics were identified in crops given to chickens, in chicken feces 83.55% of plastics found were macroparticles, and in earthworm gizzards, microplastic particles less than 50 microns werefound in 80-90% of the samples studied. This evidence is a perfect portrayal of just how continuous and pervasive the cycle of plastic pollution can be, and this may indicate the idea of plastic pollution traveling through the food chain.

However, not only are larger organisms higher up on the food chain affected by microplastics, but microscopic organisms such as zooplankton have been found to ingest microplastics, as described in a study by Plymouth Marine Laboratory. Using a highly sophisticated technique known as coherent anti-Stokes Raman scattering (CARS) microscopy, researchers found the majority of the zooplankton species they tested ingested microplastics through a process of filter-feeding. Furthermore, they realized certain microscopic particles adhered to the external surfaces of the specimen. Consequently, as they increased the concentration of microplastic particles in their experiment they found a correlation between the ingestion of microplastics and the reduced rate of ingestion of algal prey. Additionally, current research discovered that surface waters polluted by microplastics can hinder the rate of respiration and photosynthesis for plankton species, which are the base of aquatic food webs and contribute to approximately 70% of Earth's oxygen levels (National Geographics report).

Let's think about these results. If these small organisms make up the base portion of aquatic foodwebs, and are currentrly being directly affected by microplastic pollution both by increased fatality and possible bioaccumulation up the food chain, what could this mean for us? Although scientists still do not have the answers to this question, marine and environmental scientists globally are working hard to find the answer before it is too late.

There are no organisms within the food chain safe from the dangers of microplastics. They are entangled by, swimming with, and ingesting microplastics at astonishing rates.