Microplastic Pollution in Marine Ecosystems

 

Junjie Chun, Jessica Rambao, Ian Rohac

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Abstract

 

            Microplastics can be found all throughout the world’s oceans and can negatively affect many types of ecosystems. There have been many scientific studies that focus on microplastics, how they affect various organisms, where they can be found in high levels, how to capture and extract them, and how they travel from rivers and wastewater plants to the bottom of the sea. This literacy review attempts to capture the essence of over ten different scientifically valid articles all relating to microplastics and their effect on marine ecosystems in an effort to boil down and concisely point out the major themes and points of knowledge as they relate to the subject of microplastics.

 

 

 

 

 

 

 

 

Introduction

Plastics were invented over 110 years ago and are now one of the most commonly used materials by humans. In the last 60 years, plastic production increased dramatically across the globe from 0.5 million tons per year to around 300 million tons in 2013. At first, plastic was thought to be a harmless material, but after several decades, some plastics were found to contain harmful chemicals that could pollute the earth. Plastic pollution now poses a serious threat in the marine environment if it is not disposed of or recycled properly. Any piece of plastic can erode to a very small size. If any piece is less than 1mm in diameter, it is considered a microplastic. They are so tiny that they are almost invisible to the human eye and they can easily make their way through the food chain (Worn, B.,2017).

Any piece of plastic, both large and small that enters the oceans can be eroded slowly into sizes that are anywhere from 1 to 100 nanometers in diameter. More specifically though, the microplastics that are found in face wash, soaps, and shower creams are manufactured to a small size to begin with and have been found to evade filtration systems at water treatment plants and are discharged directly into oceans. However, even though these types of microplastics have received much media attention, they are only a small fraction of the estimated total level of microplastics in the ocean. The main issue with plastics of this size is that marine wildlife can mistake them for food. Once ingested, the plastics can cause gut blockage, physical injury, changes to oxygen levels in cells in the body, altered feeding behavior and reduced energy levels, impacting growth and reproduction (2016, Alexander-White). Even worse yet, the plastic particles can act as carriers by absorbing and concentrating toxic chemicals present in the environment. This can have a domino effect and can impact entire ecosystems. The impact can be as far-reaching as affecting human food supplies because of land organisms consuming the poisoned marine organisms.

According to the 2018 article in the Environmental Research Letters journal by van Sebille and others, there is an estimated 93-236 thousand metric tons of microscopic plastic debris currently floating on the sea surface. However, according to an article in the Science journal from that same year, in 2010 alone, 4-12 million metric tons of plastic is thought to have entered the oceans, which would seem to question the total sea-surface data estimate.

Methodology

We found 12 different scientific studies that explained various sub-topics within our main topic umbrella of microplastic pollution in the marine environment. We used various article search websites such as the City College of New York Academic Search Complete, City College Library OneSearch, and also Google Scholar. To narrow our searches within Google Scholar, we made sure to select the CUNY City College Library databases from the library links setting. To further narrow our search to find only recently published studies, we limited our searches to articles published after 2014 or 2015. Once the articles were populated in the search tools, we were careful to weigh the year published with the number of times that the study was cited. This made sure that we selected only well written and validated studies to filter out the studies that were less accurate or provided limited information. Search terms that we entered into the database systems included: microplastics, marine, sediments, pollution, ocean, water, and sea.  A majority of the studies focus on understanding the correlation between these microplastics and their ability to interact with other environmental contaminants, the transport routes and possible places of deposition of this debris, and the development of detection methods and analytical techniques for the presence of these particles in marine environments.

 

-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

What is plastic made of?

Plastics are chains of polymers linked together during manufacturing processes. The polymers that plastics are made from are often made of carbon and hydrogen. Sometimes they are made of oxygen, nitrogen, sulfur, chlorine, fluorine, phosphorus or silicon. In general, plastic is lightweight and can be quite strong. They can be molded, extruded, blown, turned into foams, and can even be drawn into fibers for use in textiles. (Avio, C. G., Gorbi, S., & Regoli, F., 2016).

Toxic Effects

Plastic can contain many different types of chemicals including, but not limited to, monomer residues, plasticizers, color agents and flame retardants. These chemicals can be made out of substances such as: polychlorinated biphenyls, polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons, organochlorine pesticides, polybrominated diphenyl ethers, alkylphenols, bisphenol A, and metals (Avio, C. G., Gorbi, S., & Regoli, F., 2016). These substances are toxic upon digestion and may accumulate in fatty tissues. B. Worn and others pointed out that toxic effects on marine ecosystems are less commonly known about than human ingestion mostly because it requires more experimentation and research. Throughout many experimental trials, the researchers had demonstrated the toxic impacts of chemicals that had leached from the plastic materials. One example given was that of fish that had been exposed to water that contained a high grade polypropylene. The fish end up with elevated levels of nonylphenol and suffered an increase in short and long-term mortality (Worn, B.,2017).

Microplastics in the marine environment are ubiquitous, can leach toxic additives, enter food webs and chains, and yet their fate in the marine ecosystem is poorly understood. Review of the available research articles on microplastics in the marine environment is important because it helps in making meaningful comparisons and monitoring; crucial for defining the best criteria to estimating the abundances, distribution, and composition of microplastics. Policymakers and environmentalists can also use the information to develop policies and monitoring programs that will benefit from the standardized procedures for sampling and sorting microplastics.

Experiment on Microalgae

Microplastic particles can also induce toxic effects on microalgae. Not only that, but it affects their population sizes, photosynthetic activity, and reactive oxygen production, among other things. Even though plastic debris poisons them, microalgae can also colonize them and interact with their particles by changing their properties. This can potentially affect the microplastics’ environment as well as behavior and toxicity (Prata et al., 2018). Due to this, Prata and others designed an experiment in order to effectively see the toxic effects as well as the interaction with the microplastic. In more specific terms, the study was designed to investigate if microplastic had any influence with the toxicity of doxycycline and procainamide to Tetraselmis Chuii (T. chuii), a marine microalga. (Prata et al., 2018).

The experiment was conducted with a limited number of microalgal species. They tested substances and chemicals other than microplastic. They purchased various other chemicals to also test with the T. chuii. Most of these chemicals were purchased from Aldrich and Merck in Germany. The T. chuii parental culture was kept in a controlled environment under a fixed temperature of 20℃ and in periods of 8 hours of dark and 16 hours of light. The culture medium, was prepared with seawater from the Northwest coast of Portugal, which was filtered through glass filters. A culture medium is essentially a substance in which microorganisms or bacteria are grown.This was continually fed with a sterile 121℃ air supply every 35 minutes. Every three days the culture medium was replaced in order to keep it in an exponential growth phase. In order to prevent aggregation and sedimentation of the T. chuii, the culture was shaken twice a day. They were kept no more than 2 weeks and the average growth rate per day in the laboratory was 4 days because the bioassays ranged from 0.59 to 0.03 of the increase in cell number per day.

A total number of three independent bioassays, which is the measurement of the concentration of a substance, were conducted to see the effects of microplastic and other substances. However, we are only interested in the procedure and results involving microplastic alone. When microplastic was treated alone, it tested the effects with one control and a total of seven of different concentrations of microplastic. The concentration for microplastic are as follow: 0.75, 1.5, 3, 6, 12, 14 and 48 mg/l. A total of three culture replicates were used for all the bioassays and each treatment was infuse with the proper volume of T. chuii that will give a final concentration of 1 X 10^4 cells/ml in a test medium (Prata et al, 2018). They all had the initial exposure of zero hours and a final exposure of 96 hours, in where culture samples, water pH, temperature and dissolved oxygen were collected and measured at the start and end of the bioassays. Lastly, once the exposure period ended, the samples were observed by fluorescence microscopy.

Results of the Experiment

According to the results, it was found that the percent of deviation of microplastic was a decay higher than 20 percent. There were no significant differences in the mean percentages of decay with different concentration of microplastics. This would mean that the concentration of the particles did not have any effect on the decay (Prata et al, 2018).The reduction of the particles could have been due to aggregation, followed by sedimentation, absorption of the plastics to the glass walls of the beakers. The decrease of the concentrations and test medium pH may be due to the interacting with microalgal. This experiment was not exclusively about microplastic alone but also the way it reacts with other substances. It was found that microplastics influence the processes responsible for the decay activity of certain chemicals (Prata et al, 2018).

When the experiment was done it was found that microplastics do significantly inhibit T.chuii growth rate. It was also found that the microplastics were slightly toxic, to T. chuii and that the presence of microplastics increases the toxicity of other substances. Although they concluded that microplastic did not affect the T. chuii growth rate up in amounts up to 41.5 mg/l, we still need to keep in mind that this experiment was done in a controlled environment (Prata et al, 2018). Prata and others also argue the same thing, they said that in the wild, the natural population is exposed to many different non-organic substances that may act differently on them compared to what occurred in the control environment. It was also said that more studies have to be done to further the data on the effects on microplastic and mixtures of substances on the marine environment.

 

In Plastics and microplastics in the oceans: From emerging pollutants to emerged threat, the researchers talk about the threats of microplastic. The first report of microplastic debris was in the 1970s and with ever increasing global plastic production, more and more microplastic is entering the world’s ecosystems. In terms of the present day, plastic has accumulated in terrestrial environments such as the sandy shores, desolated islands, and even the deep sea. The reason they are in various environments is that they move or migrate. By using drifting buoys and physical oceanographic models we can have an idea of where the plastic will end up. In the article written by Avio and others it says that this model shows that “plastic pollution could quickly migrate from the U.S. Eastern seaboard to the North Atlantic Subtropical Gyre in less than 60 days.” They say that a lot of plastic debris has been mainly found on the surface because of its density. Another model, the oceanic circulation model, can predict the possible accumulation region in five subtropical oceans (Avio, C. G., et al,  2016).

Nocuous effect of microplastic

The article titled, Microplastic pollution, a threat to marine ecosystem and human health: a short review, says that, due to their small sizes, microplastics can be ingested by coral, lobsters, sea urchins, zooplankton, worms, seabirds, turtle, crustaceans, and fish, among others. This can be very harmful and can cause serious disease and damage if ingested. Microplastics can have such effects as clogging of intestinal tracts, the inhibition of gastric enzyme secretion, suppression of feeding due to satiation (where the organism feels “full” because they consume too much plastic), imbalance of steroid hormone levels, delay in ovulation and infertility, and of course mortality (Sharma, S., & Chatterjee, S., 2017).

 

Transfer to the Food Chain

The transfer of pollutants to the food chain due to ingestion is not the only problem that we face.  Also of a growing concern is the capacity of microplastics to absorb pollutants from the water. Because there are so many of them that float on the ocean, they are effective in absorbing hydrophobic pollutants from water. A very low concentration of persistent organic pollutants found in marine habitats are absorbed by microplastics (Sharma, S., & Chatterjee, S., 2017).

Not only do phytoplankton and coral consume microplastics and absorbs their toxins, but many other types of marine life become affected by eating those organisms. If contaminated microplastic is exposed to harmful algae, they can produce phycotoxins that indirectly affect human health. Phycotoxins are stored within the algae and can then transfer to other organisms when they consume the algae. This can eventually lead to diarrhetic and paralytic shellfish poisoning in humans if the toxic algae is transferred to other parts of the food chain by being consumed by shellfish (Sharma, S., & Chatterjee, S., 2017).

-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

Global Distribution

The article by T. Palanisami and O. Solomon, Microplastics in the marine environment: current status, Assessment methodologies, impacts, and solutions from 2016, indicates that microplastics are found throughout the water column (vertically and horizontally) in the oceans. However, it is difficult to identify the primary source of these plastics due to their fragmentation, and degradation. Low-density microplastics such as polyethylene and polystyrene predominate the ocean surface, while high-density microplastics, including poly-esters and poly-vinyl chloride, are found in the benthos. Microplastics on the surface of the water are mostly sampled from the Pacific and North Atlantic oceans, and the Mediterranean sea due to concentration and widespread distribution in those regions. The environmental transport processes of microplastics starts at manufacturing industries. Our society uses plastic products and disposes of them improperly, that is how they get into soil and water. The waste which has perhaps accumulated in soils is carried to the seas and oceans through water runoff and soil erosion. Industries also release untreated wastes directly to the rivers which transport them to the marine sources. While in the oceans or seas, the plastic sediments undergo retention and finally deposition.

Measurement Methods of Microplastics

According to the article by M. Thiel, R. Thompson, L. Gutow, and V. Hidalgo-Ruz titled, Microplastics in the Marine Environment: A Review of the Methods used for Identification and Quantification, there are four main sampling techniques used in identifying and quantifying microplastics. Those procedures include density separation, filtration, sieving, and visual sorting of the plastic particles.

The sediment samples used were mainly obtained from the sandy beaches at high tide line while the seawater samples were obtained from the sea surface using neuston nets which are large rectangle net frames for sampling substantial water volumes. This article answered multiple questions related to the criteria for the sorting of plastics, i.e., color, plastic type, shape, and the degradation stage, among others. The researchers found, through infrared spectroscopy, that most microplastics are chemically composed of polyethylene and polypropylene polymers, and the size ranges between 1-500 micrometers (Thiel et al., 2017)

 

 

Sampling Technique

Mass processing and sorting of microplastic samples in the laboratory proved crucial for bulk and sample sizes. They found that the typical density for plastic particles, particularly polypropylene, ranges between 0.8 to 1.4 grams per cubic centimeter while polystyrene ranges between 0.05 to 1.0 grams per cubic centimeter (Thiel et al., 2017). Filtration, conducted after density separation, uses filter papers with pores of different sizes. Once filtered, the microplastics were picked out of the filters using tweezers. The researchers noted that the samples could become contaminated during the filtration procedure and so they said that it was important to seal the filters in petri dishes during drying. The filtered microplastics are then sieved and sorted visually and separated. The study revealed that microplastics can have wildly differing sizes and can have varied shapes and physical features that affect their buoyancy and toxicity to organisms.

Impacts on Marine Products

The authors of the 2017 article, Microplastic Pollution in Table Salts from China, L. Lan,  D.Yang, H. Shi, L. Jiana, J. Khalida & P. Kolandhasamy, indicate that microplastics can be found in all seas worldwide, and thus sea salts can have microplastics mixed in. Research was conducted to test the hypothesis that sea, lake, and rock salts from supermarkets in China had microplastics within them. The study found that lake salts had microplastics in amounts ranging from 43 to 364 particles per kilogram while the sea salts had 550 to 681 particles per kilogram. They also found that fragments and fibers were the most common shapes of microplastics in the salt as compared to pellets and sheets.

They found that the type of microplastic that was most common in sea salts was polyethylene terephthalate. They also found that seas were more contaminated by microplastics than lakes and ponds (Lan et al., 2017). The study concludes that the indiscriminate disposal of plastics in the ocean puts a heavy burden on waste management systems, can lead to ecosystem infiltration, and, when people feed on sea products, they can potentially raise their risk of getting serious diseases such as cancer.

The 2018 article titled, Microplastics: An Introduction to Environmental Transport Processes,written by A. Horton & S. Dixon, provides an overview of the knowledge relating to the sources, fates, pervasiveness, persistence and potential impacts of microplastics in the marine environment. Understanding the processes through which plastics accumulate in the seas and oceans helps in the assessment of and aids to determine the likely-long term ecological and human health implications of microplastic contamination.

The article also shines some more light on exactly how microplastics affect the marine organisms that consume them. The physical microplastic particles themselves can have many negative effects on organisms including chemical toxicity, bioaccumulation, inhibition of growth, impaired reproduction, and abrasion or tissue damage among others. When plastics are ingested, they can release toxic substances that affect the amount of microbial DNA and may lower the diversity of microorganisms such as bacteria. Although not scientifically proven, we are lead to believe that microplastics may have similar negative effects on humans. But, we found that more research needs to be done in that respect.

Articles Critique

The above articles have revealed the potential risks that microplastics pose to marine life. Plastic is an integral part of people’s everyday life and thus many tons of plastics are manufactured each year. Introducing rules or policies to prohibit the production of plastics could hurt the economy before we precisely understand what their true effects are to humans, animals, and ecosystems. But, these studies do show that microplastics, at high concentrations can cause severe damage to the marine environment.

However, there are knowledge gaps in the research. For instance, there are difficulties in determining exactly what impacts are due to microplastics, and those that possibly result from other stress factors in the marine environment although the uncertainty should not be considered as a reason for not reducing plastic pollution levels. We feel these articles fail to address what can be done about plastics ending up in the seas and oceans. Perhaps humans should begin manufacturing only biodegradable plastics. However, maybe the researchers are being realistic in the sense that they know that it will not be easy to wean the world off plastics and that they can also be very difficult to clean up.

-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

How does buoyant microplastic sink to the sea floor?

We began to dig a little deeper into the science behind microplastics, why they are found where they are found, and how they got there. We came across an article in the Environmental Science & Technology journal titled “Role of Marine Snows in Microplastic Fate and Bioavailability” published in May of 2018 detailing a few ways that microplastic can become more available to marine organisms. It mentions that plastic particles that should float on the sea surface have been reported at depths down to 5000 meters, in ocean sediments, and within some deep-sea organisms. The article explores a key environmental factor that can alter the densities of the plastics, the formation of marine snows. Marine snows are “organic-rich aggregates made up of fecal pellets, larvacean houses, phytoplankton, microbes, particulate organic matter (POM), and inorganics brought together by shear forces and Brownian movement (van Sebille, et al., 2018)” (Porter, Lyons, Galloway, & Lewis, 2018). They are primarily responsible for the movement of organic material from the surface waters to the benthos. (Benthos or benthic meaning: of or relating to the bottom of a body of water, e.g., at/in the sediment surface) The plastic particles that float on the surface and within the upper layers of the ocean can get caught and incorporated into these marine snows, taking them down to the deep sea and eventually landing on and mixing with the seafloor sediments. For all polymer types and shapes tested, they measured enhanced sinking rates when they were incorporated into marine snows compared to if their sinking rates as free particles.

Most importantly, particles that normally float in water, once incorporated into marine snows, sank. The real-life application of this discovery is that the particles that once floated on the surface may have been relatively easy to clean up with filters or strainers, but once they sink below the surface, those particles become near impossible to find and collect. In order to collect the sink rate data for the different plastics, they simply measured how fast the free particles sank versus how fast the particles within marine snow sank in a static water column in a laboratory.

We found it to be quite revealing and truthful of them to reinstate for the reader that the sinking rates for the microplastic particles they found were based on simple models for a static water column and the observations for the plastics incorporated into marine snows were taken under similarly static conditions. They highlighted that the values could not be taken as true particle sinking rates as if in the real-world oceans. Therefore, they expect their sinking rates are higher than those reported in the natural environment where turbulence acts to slow the rates. However, they do say that the benefit to using the controlled static system is that they can compare the sinking rates for the polymers that they tested against the standard, modeled sinking rates for free plastic particles without complex real-ocean conditions. This allows them to easily test their hypothesis.

The team of scientists also demonstrated that the incorporation of microplastics into marine snows increases their bioavailability to a model benthic filter feeder, the blue mussel (Bioavailability simply meaning how available something is, to biological, organic organisms). As expected, the average number of microplastics ingested per mussel increased dramatically if the marine snow was contaminated with the plastic particles versus simply being free plastic. Moreover, the average increased even more, when the plastic was simply floating with the marine snow, and not incorporated in it.

Finally, the article mentions that the researchers conducted a mini literature review of their own, on microplastic pollution in benthic samples. They found that of all the microplastics collected from subtidal sediments, around 46% of them were buoyant polymers, and of all microplastics found in benthic organisms, 8% were also buoyant (Porter, Lyons, Galloway, & Lewis, 2018). This data is interesting because it further validates their findings in the sense that marine snows seem to be a possible cause of otherwise buoyant microplastic particles finding their way below the surface of the water and into benthic organisms.

Microplastic pathways to the world’s waters

There are many different pathways that microplastics can use to enter the ocean, but an article from the Environmental Pollution journal specifically goes on to research and detail how they can make their way through municipal wastewater treatment plants and into the sea. The article, titled “Microplastic pollution is widely detected in US municipal wastewater treatment plant effluent,” was published in 2016 and it was written by Sherri A. Mason, Danielle Garneau, Rebecca Sutton, Yvonne Chu, Karyn Ehmann, Jason Barnes, Parker Fink, Daniel Papzissimos, and Darrin L. Rogers. By averaging 90 samples from 17 different facilities across the United States of varying size, populations served, and filtration types, they found that there were about 0.05 microparticles per liter of effluent. Effluent is the liquid waste or sewage that gets discharged from the facilities in a river or sea. To be modest, we believe taking samples from only 17 facilities among thousands of others in the US would not give a very accurate representation of the true amount of microplastics being discharged. On top of this, the researchers only visited treatment facilities in Northern California, Eastern Wisconsin, and Central and Eastern New York. We believe the sampled locations would also not give a very accurate representation of the true data as they do not take many samples from the Central or Southern United States. Regardless, we do need to keep in mind that it is only a rough estimate and the study does give other useful information on the types of microparticles found and how they make their way through the systems.

They collected their water samples just before the effluent was discharged through sieves over a period of 2 to 24 hours. They took into account the time elapsed and also the flow rate during that period to determine the volume of effluent that was sampled. For each sample, they transferred the sieve contents into separate containers and immediately preserved them in 70% isopropyl alcohol for later laboratory analysis. In order to process the samples, they digested the organic matter using 30% hydrogen peroxide and then transferred what remained through a sieve and into a petri dish for visual analysis under a microscope. They removed all microplastic particles and counted and categorized them. The researchers used a variety of processing and detection methods for plastic pollution within environmental samples. They relied on a method developed and supported by the National Oceanic and Atmospheric Administration Marine Debris program. So, we do know that they attempted to collect their data in a valid and supported way as to be as accurate as possible.

In summary, the researchers found that, on average, municipal wastewater effluent contained less than one particle per liter, with values from 0.004 to 0.195 particles per liter (Mason, et al., 2016). Even though that value does seem low, the article mentions that these facilities process millions of liters of wastewater per day, the estimated daily abundance of particles released within the effluent was found to be quite high, around tens of thousands to millions of particles per day. When they average that over the 17 facilities, they found that about 440,000 particles were released per facility per day. However, due to the visual inspection technique used in their analysis methods, they cannot assume that all fibers in these samples were plastic. They mention however that Lenz et al. (2015) noted that “75% of fibers identified by visual inspection as plastic in marine samples were later verified as plastic via spectroscopy”, so the data remains fairly valid. In short, given the prevalence of microbeads within personal care products, synthetic fibers that get washed out of clothing and fabrics, and the fact that wastewater treatment facilities were not designed with future-proofing in mind to remove new contaminants such as microplastics, their findings were consistent with their expectations. There was an overall concerning amount of microplastic pollution from these treatment plants that made its way into the world’s rivers and oceans, which as we know, can be dangerous for not only the health of our environment but also for human well-being. Finally, as we look through the funding sources for this study, we do find that there is an obvious correlation between the locations of the sampled treatment facilities and the locations of the monetary sources. Partial support was provided by the State University of New York, SUNY Fredonia, SUNY Plattsburgh, and the Regional Monitoring Program for Water Quality in San Francisco Bay. These are in the same or similar locations to the areas that were sampled for microplastic in the effluent.

Small-Scale Portable Microplastic Extraction

Research is still being conducted on microplastics effect on the environment and the organisms within it. In order to gain a clear understanding of microplastic availability to marine life, and the risks to the biological process that are associated with it, accurate measures of microplastic abundance in sediments need to be obtained. Currently, due to costs, impracticalities, and/or inefficiencies associated with existing methods of microplastic extraction, there is a lack of reliable benthic abundance data for microplastics. Because of this, the researchers involved in the article titled, “A small-scale, portable method for extracting microplastics from marine sediments” in the Environmental Pollution journal are trying to promote practical, accurate, and standardized sampling, preparation, and detection methods.

They mention that there was already a Munich Plastic Sediment Separator (MPSS) that isolated microplastics from sediment with recovery rates of 95.5% (Coppock, Cole, Lindeque, Queiros, & Galloway, 2017). However, they said that because it was very large, used expensive materials, and was designed for large quantities of sediment, it was costly to produce and impractical for processing many smaller sample sizes. Thus, they set out to create a smaller, cheaper, yet a just-as-effective version of the MPSS. For their new Sediment-Microplastic Isolation (SMI) unit, they used a 38 centimeter tall plastic tube cut in the middle with a ball valve combining the two halves. Inside of the tube, they needed a floatation media, meaning a liquid that they could use to allow the sediment to sink, and the polymers to float. Keeping cost in mind, they tested three different salts to determine which salt gave the best solution density versus cost ratio. They tested many different sediment types, such as both fine and coarse clay, silt, and sand from sounds, rivers, beaches, and estuaries. Also, before, during, and after each step of assembly, processing, and cleaning, the researchers made it extra clear that they properly cleaned, sanitized, purged, and maintained all components of the SMI unit. They even included an entire section in the article titled “Contamination Control” wherein they mention that, among other things, they implemented contamination controls and procedural blanks during the field sampling and processing as per the protocols of Lusher et al., 2016.

The researchers in this study concluded that, because sodium iodide (NaI) was too expensive, and sodium chloride (NaCl) did not provide adequate relative densities, zinc chloride (ZnCl₂) was deemed the most appropriate salt solution for the floatation of microplastics using their SMI unit. The unit itself is both compact and portable and it can extract many different forms of microplastics from a variety of sediment types. They do mention that long-term use has not been tested in the study and that, eventually, the ZnCl₂ could degrade the unit. However, with regular inspection and testing of the unit, if any contamination is found, it could be replaced at the cost of around GBP £50. Overall, the mean extraction efficiencies that they found were between 92 and 98% which is certainly comparable to the MPSS which had a 95.5% recovery rate (Coppock, Cole, Lindeque, Queiros, & Galloway, 2017). This study has opened up many new possibilities for further, more cost-effective research on an increasingly dangerous material threatening our environments. The project was funded by the Natural Environment Research Council and the Marine Ecosystems Research Programme.

 

Microplastic in Arctic Deep-Sea

In 2017, an article in the Environmental Science & Technology journal was published detailing findings of microplastic deep in the arctic seas by the HAUSGARTEN Observatory. The observatory has 21 permanent underwater stations covering depths between 250 to 5500 meters in the eastern Fram Strait. The researchers used the stations’ video guided multiple corers to obtain many, virtually undisturbed core samples from the ocean floor. They used nine different station samples in various areas of the Arctic seabed, including some from the Molloy Deep, which is the deepest part of the Arctic Ocean. They made sure to freeze the cores in tin foil as soon as they were obtained from the stations. Then, they characterized and separated all of the microplastics within the sediments using the MPSS with a ZnCl₂ ­­­­­solution as a flotation medium for the plastic.

Once they obtained all of the microplastic samples, they used stereo-microscopes to visually sort the microplastics by size first. Then, they used attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) to analyze the plastics and categorize them by type. They even mention that some of the data was processed by automated analyses of the μFTIR data. Each pixel from the spectroscopy was identified and stored into a file which was analyzed by Python 3.4 scripts and Simple ITK functions. The researchers say that it enabled the identification and quantification of all polymer particles and excluded human bias. Like many other reputable studies of this type, they have an extensive section on how they protected their samples and data from contamination by, among other things, using only glass and stainless-steel labware and cleaning them with sterile chemicals before and after each step.

The researchers mentioned that microplastics were detected in all sediment samples with an average of 4,356 particles per kilogram of sediment. They identified 18 different polymer types in total with between 5 and 14 different types per sample. The results of this study indicated higher microplastic abundance in the Fram Strait than in all other sea-floor regions investigated in the Arctic ocean to date. They say that their methodical approach allowed them to detect an unexpectedly high number of microplastics in sediments from the deep Fram Strait, especially in the small-size range of fewer than 500 micrometers per particle. They go on to compare their magnitudes of microplastics detected with previous studies from other parts of the world. They found that reported quantities elsewhere were 16 times lower in the Atlantic Ocean, the Mediterranean Sea, and in two subarctic samples taken nearby, Southwest of Svalbard. The researchers mention that the methodology may differ in those studies which could account for some of the differences, but regardless, the high abundance in their samples is still striking. It was suggested that a significant fraction of the microplastic debris likely originated from Northern Europe and made its way North with Thermohaline Circulation (THC is large-scale ocean circulation driven by global density gradients created by surface heat and freshwater fluxes). Even still, local sources may also contribute to this since highly-polluting human activities such as fishing and tourism have increased due to the receding sea ice. Moreover, they say that the release of microplastics from Arctic sea ice during melting may contribute as well, but it still has to be verified by analysis of samples from year-round particle traps (Bergmann, Wirzberger, Krumpen, Lorenz, Primpke, Tekman, & Gerdts, 2017).

 

 

Conclusion

Microplastics contaminate global oceans and are accumulating in sediments at levels thought sufficient to leave a permanent layer in the fossil record. They are pervasive pollutants of the global marine environment and they have been recorded from the surface to the seafloor and from the tropics to the poles. They have also been found in the guts of over 300 different marine species. This prompts widespread concern over the plastic’s environmental impact.

Quantitative estimates on the global abundance and weight of drifting plastics are still limited. This is particularly for the Southern Hemisphere and other remote regions. A high number of marine species are known to be affected by plastic contamination, which can lead to a larger ecological risk. Therefore, as it should, assessment of these contaminants’ materials have become a research priority. Besides ingestion, microplastics can accumulate in planktonic and invertebrate organisms, which are then later transferred up the food chains, and in some cases, all the way to humans.

According to the themes revealed by our research, the prevention of harm of microplastics should start right from the industries. But that is not all, society at large needs to be educated on the harm that microplastics can induce in our world. They need to understand that eventually, it can begin to affect us humans in ways larger than we can imagine. Soon after, we should start to gather funds to begin worldwide cleanup. Scientists and policymakers should focus on upstream control measures such as zero waste strategies, improvements in wastewater recovery, and directly managing and mitigating sources of microplastics. Plastic pellet production should be regulated and microplastics in cosmetics can be replaced with biodegradable alternatives. Effective Microplastics measuring techniques should be used as well.

By doing all of this, we can begin to reduce the harm that humans have already done on our earth. Some of the effects may never be erased, but we can help to clean up and reverse some of the terrible consequences of our actions thus far and hopefully change the future health of our oceans for the better.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

Alexander-White, C. (2016, November 15). The massive problem of microplastics. Retrieved from Education in Chemistry.

 

Avio, C. G., Gorbi, S., & Regoli, F. (2016, May 15). Plastics and microplastics in the oceans: From emerging pollutants to emerged threat. Retrieved October 15, 2018

 

Bergmann, M., Wirzberger, V., Krumpen, T., Lorenz, C., Primpke, S., Tekman, M. B., & Gerdts, G. (2017). High Quantities of Microplastic in Arctic Deep-Sea Sediments from the HAUSGARTEN Observatory. Environmental Science & Technology, 11000–11010.

 

Coppock, R. L., Cole, M., Lindeque, P. K., Queiros, A. M., & Galloway, T. S. (2017). A small-scale, portable method for extracting microplastics from marine sediments. Environmental Pollution, 829-837.

 

Horton, A & Dixon, S. (2018). Microplastics: An introduction to environmental transport processes. WIRES Water, vol. 5(2).

 

Lan, L., Yang, D., Shi, H., Jiana, L, Khalida, J & Kolandhasamy, P. (2017). Microplastic Pollution in Table Salts from China. Environmental science and technology 2015, 49(22).pp. 13622-13627.

 

Mason, S. A., Garneau, D., Sutton, R., Chu, Y., Ehmann, K., Barnes, J., . . . Rogers, D. L. (2016). Microplastic pollution is widely detected in US municipal wastewater treatment plant effluent. Environmental Pollution, 1045-1054.

 

Palanisami, T & Solomon, O. (2016). Microplastics in the marine environment: current status, Assessment methodologies, impacts, and solutions.

 

Porter, A., Lyons, B. P., Galloway, T. S., & Lewis, C. (2018). Role of Marine Snows in Microplastic Fate and Bioavailability. Environmental Science & Technology, 7111-7119.

Prata, J. C., Lavorante, B. R., Da ConceiÇão Montenegro, M., & Guilhermino, L. (2018, February 21). Influence of microplastics on the toxicity of the pharmaceuticals procainamide and doxycycline on the marine microalgae Tetraselmis chuii. Retrieved October 15, 2018.

Sharma, S., & Chatterjee, S. (2017, September). Microplastic pollution, a threat to marine ecosystem and human health: A short review. Retrieved October 15, 2018.

Thiel, M., Thompson, R., Gutow, L., & Hidalgo-Ruz, V. (2017). Microplastics in the Marine Environment: A Review of the Methods Used for Identification and Quantification.

Worn, B., Lotze, H. K., Jubinville, I., Wilcox, C., & Jambeck, J. (2017). Plastic as a Persistent Marine Pollutant. Retrieved October 15, 2018.

do we need this thingys?