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Detecting Microplastics in the Marine Environment

By: Amy Uhrin, Chief Scientist with the NOAA Marine Debris Program

Microplastics are a type of plastic marine debris that are less than five millimeters in size. Research on this type of debris has become more widespread, but since there is no single agreed-upon method for separating, counting, and weighing microplastics in water samples, it is difficult to compare results across studies. Common approaches may be used, but most laboratories develop their own procedures based on factors such as budget, equipment availability, labor, and the specific research questions being asked.

Since so many different protocols are being used, the NOAA Marine Debris Program partnered with researchers at the University of Washington Tacoma to compare different methodologies.  Six labs from around the globe were chosen for this comparison, each having experience in processing water samples for the purpose of counting microplastic particles. Reference samples were created by first filtering water collected from the Thea Foss Waterway in Tacoma, Washington, and then adding a known number and weight of microplastic pieces to 200mL of the filtered water. The types of plastic pieces added to the sample included fragments from drinking straws, netting, sandwich bags, and other common plastic items. These reference samples were shipped in glass jars to participating laboratories for analysis. The labs were asked to use their own methods to process the sample and report the number of particles counted and the total weight of the particles.

The overall accuracy of the protocol comparison was high. Microplastic weights measured by the participating labs differed by only 1.6% on average from the reference sample. There was also high agreement in the particle counts made by each lab versus the reference samples. Projects such as this that evaluate the comparability among labs are a first step toward the development of standardized microplastic sampling methods for the collection of reliable and comparable data. To our knowledge, this is the first interlaboratory comparison for microplastic sampling methods.

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Influence of Various Aqueous Conditions on Additives Releasing From, and Pollutants Sorbing To, Microplastic Debris

This week marks “Research Week” on our blog and we will be highlighting marine debris research projects throughout the week! Research is an important part of addressing marine debris, as we can only effectively address it by understanding the problem the best we can.

By: Rob Hale, Guest Blogger and Professor in the Department of Aquatic Health Science at the Virginia Institute of Marine Science (VIMS)

Plastics are an increasing problem in our ocean and waterways. The plastic products we use, and hence those that find their way into the environment, are made of different polymers. These include products ranging from disposable water bottles, fishing gear, electronics, microbeads from personal care products, to furniture. Chemical additives are inserted into many plastic polymers to modify plastic properties such as color, flexibility, weather resistance, and flame retardancy. These additives may leach out over time, depending on the chemical structure of both the plastic polymer and the additive. Unfortunately, some additives are persistent, bioaccumulative, or toxic. In addition, pollutants already in the water, such as polychlorinated biphenyls (PCBs), can sorb to the surface of plastic debris. After exposure to light or abrasion, plastics fragment into ever smaller particles called microplastics. Microplastics can have different shapes and sizes, which not only affect their leaching and sorption behavior, but can influence what organisms either intentionally or inadvertently consume them. Knowledge of the relative importance of all these factors is critical to our understanding of the effects of discarded plastics in our ocean.

Figure showing that additives may leach out of plastic particles over time, while other contaminants can sorb to plastic particles.

Additives may leach out of plastic particles over time, while other contaminants can sorb to plastic particles. (Credit: NOAA)

We chose to study these interactions and used a laboratory environment so we could individually control the factors of interest. We investigated different combinations of plastics (polyurethane foam, polyethylene, polystyrene, and polyvinyl chloride or “PVC”), additives, and water pollutants. We also examined the effect of microplastic size and the degree of weathering. We first ground various types of plastics to different size ranges using an ultra-cold grinder to make them brittle (check out this video of the process). Following the grinding of the plastics to microplastic size, we took photos of the microplastics through an electron microscope (see image below) and measured their surface areas. The plastics were then weathered by being exposed to ultraviolet light, as they might experience at the water’s surface or on a beach. Next, we placed a small amount of weathered or unweathered microplastics in a column containing sand (see figure below) and leached them with waters of differing temperature, salinity, and organic carbon content (including imitation animal digestive fluids). The water exiting the column was then collected and analyzed to see what additives were released.

We found that the type of plastic polymer greatly affected its surface area after grinding. Smaller microplastic particles, which have a greater surface area ratio, generally released additives at an increased rate. Polyurethane foam was particularly interesting due to the amount of flame retardants released to the water. Salinity had little effect on additive leaching. In contrast, higher water temperature, such as found in the tropics and the digestive tract of warm-blooded animals, caused more chemicals to be released. Leaching the microplastics with water containing humic acids caused the release of even greater amounts of additives, especially of flame retardants. Humic acids are natural chemicals found in high levels in estuaries, coastal sediments, swamps, landfills, and wastewater treatment plants (where many microplastics are trapped). Leaching the microplastics with synthetic digestive fluids, similar to what occurs in an organism, caused the most additives to be released to the water.

The results of this research allowed us to distinguish what factors increase the release of potentially harmful chemicals from discarded plastics to the environment. Such information is critical to protect living resources, as well as human health. Results will also allow us to design safer plastic products in the future.

For more information on this project, check out the Marine Debris Clearinghouse and the project profile on the NOAA Marine Debris Program website, where more results will be shared soon.


Different Types of Plastic Litter Lead to Different Types of Effects in Animals

This week marks “Research Week” on our blog and we will be highlighting marine debris research projects throughout the week! Research is an important part of addressing marine debris, as we can only effectively address it by understanding the problem the best we can.

By: Chelsea M. Rochman, Guest Blogger and Assistant Professor in the Dept. of Ecology and Evolutionary Biology at the University of Toronto

When I go to the beach, anywhere in the world, I can kneel down and find small bits of plastic litter in the sand—these bits are called “microplastics.” Microplastic has become a common pollutant. It can be found globally, from the equator to the poles, in the ocean, lakes, and rivers. Microplastics are also eaten by and can be found inside nearly 700 species of animals, which likely mistake them for food.

If you take a closer look at this litter, you will notice that it is diverse— a handful of microplastics looks like party confetti, with several colors and shapes. This is because there are many types of microplastics that enter the environment. You can likely see some of the various types from looking at the plastic products in your home. Microplastics generally come from larger plastic items (like water bottles and other household items) that have been degraded into several pieces via the sunlight, wind, and waves. If you look at your plastic items, you’ll notice a recycle code which indicates the plastic type; because there are several plastic types, there are several types of microplastics in the ocean. Thus, animals in the ocean, lakes, and rivers eat a diverse mixture of this material.

Ingesting this plastic debris can be harmful to animals. But, because all plastics are not the same, we were curious how different types of microplastics may impact animals differently. To help answer this question, we designed an experiment in our laboratory that fed different types of common microplastics to prey and predators in a freshwater food chain. We chose to experiment with plastics that belong to recycle codes 1 (polyethylene terephthalate, or “PETE,” used in polyester clothing and water bottles), 4 (polyethylene, used in plastic bags), 3 (polyvinyl chloride, or “PVC,” used in plastic pipes and bank cards), and 6 (polystyrene, used in food take-out containers and disposable cutlery). Because plastics in nature also accumulate chemicals from the environment, we spiked some of these plastics with the organic pollutant, polychlorinated biphenyls (PCBs). We fed environmentally-relevant concentrations of these plastics, both with and without PCBs, to freshwater clams (prey) for 28 days. To measure how the exposure of contaminated prey may impact a predator, we then fed some of the clams to white sturgeon (predator), which are fish that naturally eat clams.

Figure showing various experimental groups fed to clams, which are then fed to sturgeon.

Various treatments were used to investigate the effects of different plastic types on prey and predators. These included feeding clams with a negative control (no plastic, no PCBs), a PCB control (no plastic, with PCBs), and then each type of plastic both without PCBs and with PCBs. Sturgeon were then fed clams exposed to each treatment. (Figure Credit: Chelsea Rochman)

We tested for several effects in clams and sturgeon exposed to each type of microplastic. We then compared these measurements to control treatments (clams and fish that were not exposed to any microplastics or PCBs). We compared changes in protein levels related to the metabolism of toxic compounds and reproduction, abnormalities in cells and tissues, changes in feeding behavior, condition factor (determined using standard weight versus length measurements, often used to measure health), and survival.

We found that the impacts to animals varied by plastic type— using several different plastics that were all the same shape and size, and we found greater overall effects from some plastic types and no effects from others. Just like chemical pollutants, our results suggest that not all microplastics should be lumped into one generalized contaminant group. Instead of only thinking about concentrations of microplastics that may be hazardous, we might also consider different sources and types of microplastics that may be hazardous. This may help ease some of the pressure on both resource managers and industry groups.

For more information on this project, check out the Marine Debris Clearinghouse and the project profile on the NOAA Marine Debris Program website, where more specific results will be available soon.


Can Tiny Plastic Particles in the Ocean Introduce Contaminants to the Food Web?

This week marks “Research Week” on our blog and we will be highlighting marine debris research projects throughout the week! Research is an important part of addressing marine debris, as we can only effectively address it by understanding the problem the best we can.

By: Amy NS Siuda (Eckerd College), Kara Lavender Law (Sea Education Association), and Tony Andrady (Helix Science), Guest Bloggers and Principal Investigators for the Research Project “Investigating the Influence of Microplastics (and contaminants) on the Grazing Behavior of Copepods”

 Can the tiniest plastic particles in the ocean introduce contaminants to the food web? This very question was at the heart of our recent research project, funded by the NOAA Marine Debris Program. As a first step to answering this question, we proposed to test whether microscopic copepods, the most abundant multicellular organisms in the ocean, would eat contaminated plastic particles.

Microplastic debris (less than 5mm) can originate from the likes of facial and body washes in the form of “microbeads,” or may start as larger, more recognizable, objects that break down into smaller and smaller pieces over time. Microscopic plastic particles can be as small as the single-celled algae that form the base of the marine food web (30 times smaller than a grain of salt!) and which are the primary diet for copepods.

A microscope image of a copepod.

An Acartia tonsa copepod, approximately 1mm long, as used in this experiment. (Photo Credit: Dam Lab, UConn)

Unfortunately, this plastic debris is often contaminated with toxic chemicals. Plastics can absorb and concentrate toxic pollutants present at trace levels in seawater, and some of the chemical additives mixed in during the manufacturing process can be toxic as well. When marine organisms ingest chemical-laden plastic pieces, some of the pollutants may be released within the gut of the animal and absorbed into body tissue. Although it is uncertain how much of these harmful chemicals enter marine animals due to ingestion of plastic debris in the ocean, laboratory experiments suggest there may be reason for concern.

Biological oceanographers often use simple bottle incubation experiments to isolate and observe interactions between microorganisms. Using this model, and using three common pollutants (nonylphenol, decabromodiphenyl ether, and dicholoro-diphenyl-tricholorethane—say that five times fast!) to contaminate select microbeads, we exposed individual copepods to one of four diets: microalgae, uncontaminated microplastic beads, contaminated microplastic beads, and a mixed diet of microalgae and contaminated microplastic beads.

Copepods in the wild tend to avoid eating naturally-toxic microalgae, so we were interested to learn if copepods exposed to a mixed diet would indiscriminately eat contaminated microbeads along with the algae, or if they would somehow sense and avoid eating contaminated microbeads altogether. If copepods eat the microbeads, there is potential for biological accumulation of contaminants that begins at the very base of the food web.

An image of a woman working in a lab around a lab setup.

Here, a bottle experiment is in progress. To keep algae cells and plastic particles well-mixed in the solution, bottles were affixed to a slowly-rotating plankton wheel in a temperature- and light-controlled room. (Photo Credit: A. Siuda)

The experiments showed that copepods ate the contaminated plastic beads and apparently were not able to distinguish between an uncontaminated plastic bead and a highly contaminated bead. This was true of all three pollutants we tested.

The experiments also attempted to figure out the fraction of beads eaten by copepods when they were presented with a mixture of plastic beads (clean or contaminated) and algae, their staple food.  However, unexpected methodological challenges complicated the data. In order to quantify the number of plastic beads and algae that were consumed during an experiment, we used automated particle counting based upon particle size. We discovered that the tiny polyethylene beads had a tendency to clump together. These clumps, together with biological debris from the algal cultures, obscured the particle size information needed to determine the number of plastic beads and algal cells that had been eaten. This result, while disappointing, revealed a previously unknown phenomenon (plastic particle clumping) and will inform future experimental designs.

Although the fraction of ingested microbeads couldn’t be determined, the discovery that copepods ate both contaminated plastics and clean plastics is an important finding. It suggests these organisms either cannot sense these particular contaminants on their food, or cannot selectively avoid food particles contaminated with toxic chemicals. Without these avoidance mechanisms, there may be toxicological effects for copepods exposed to contaminated plastics in the ocean.

For more information on this project, check out the project profile on the NOAA Marine Debris Program website and the Marine Debris Clearinghouse.


The United States of Trash: A Quantitative Analysis of Marine Debris on U.S. Beaches and Waterways

This week marks “Research Week” on our blog and we will be highlighting marine debris research projects throughout the week! Research is an important part of addressing marine debris, as we can only effectively address it by understanding the problem the best we can.

By: George H. Leonard, PhD, Guest Blogger and Chief Scientist for the Ocean Conservancy

Have you ever wondered how much trash is on U.S. beaches? So have we! At Ocean Conservancy, we have spearheaded the International Coastal Cleanup (ICC) for over 30 years and have collected data on the materials that are cleaned up each year. However, we haven’t done a rigorous, quantitative analysis of those data to provide a baseline by which to understand changes over time and spatial differences in marine debris across the U.S. The NOAA Marine Debris Program (MDP) has similarly monitored marine debris at a number of sites around the country, but also has not yet tried to rigorously evaluate what all the data mean. So, we have both teamed up with scientists Drs. Chris Wilcox and Denise Hardesty at Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia to bring the power of statistics to the problem. The answers are now just pouring in, and while we can’t reveal the specific findings until they are published in the peer-reviewed scientific literature, we can give you a sense of what is emerging from this effort.

Our joint project centered on 3 core questions: 1) How much marine debris occurs along U.S. shores?; 2) Are there specific items that are most (and least) abundant, and do they vary locally or regionally?; and 3) Are there “hotspots” where marine debris is most abundant? Our approach was to bring together the ICC and NOAA datasets and statistically explore the impact of state, region, proximity to cities, presence of rivers, and observer bias on the amount and type of debris collected. We were also interested in determining if patterns in some types of debris (like bottles and caps) were influenced by the presence of local policies, like container deposit legislation.

The analysis suggests that marine debris is highly variable around the United States, with some states quite ‘clean’ and others quite ‘dirty’, on a relative scale. While these patterns are highly variable, they are also heavily impacted by the presence of people, the location of routes to the sea (like rivers), and the presence of international borders. We are also discovering evidence that local policies, like container deposit laws, can reduce the presence of commonly-littered items (such as beverage containers) on local beaches.

The three monitoring protocols that were used in this study vary in the size of debris that is recorded. The Ocean Conservancy’s ICC methods have no detection limit (so include very small and large debris pieces), while NOAA’s monitoring efforts record items down to 2.5cm (one inch) in size. Thus, these two survey types are particularly adept at identifying larger items of littered trash. CSIRO’s approach to sampling debris quantifies all debris items that are visible to the naked eye (down to about 1mm in size), which can include many of the small plastic pieces that result from the disintegration of large debris due to exposure to the elements. Thus, when evaluated statistically, estimates of the number of plastic items on the beach can vary widely depending upon the survey method used. Of course, none of the sampling methods we evaluated are capable of sampling plastic pieces that are even too small to be seen by the naked eye. If you include these teeny plastic pieces – visible only under a microscope – estimates of how much debris litters our nation’s beaches and waterways grow larger still.

One take-home message from our study? The more scientists research the issue of debris in the ocean, the more we uncover the extent of the issue and the bigger the problem seems to become. Collaborative partnerships among NGOs, scientists, and government leaders like NOAA can help quantify the scale and scope of the problem – and in so doing, lay the foundation for the solutions needed to keep debris from entering the ocean in the first place.

For more on this project check out the project profile on the NOAA Marine Debris Program website.

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It’s Research Week on the Marine Debris Blog!

This week marks “Research Week” on our blog and we will be highlighting marine debris research projects throughout the week! Research is an important part of addressing marine debris, as we can only effectively address it by understanding the problem the best we can.

Stay tuned starting later today for a post each day about our research efforts. We’ll wrap up with a Reddit “Ask Us Anything” on microplastics Thursday afternoon! Tune in on Thursday (1/12) at 1pm EDT to check out the conversation with the NOAA Marine Debris Program’s (MDP’s) science team and ask some microplastics questions!

Meet our scientists:

Amy Uhrin, NOAA Marine Debris Program Chief Scientist.Amy V. Uhrin, Chief Scientist

Amy spent 15 years as a Research Ecologist at NOAA’s Center for Coastal Fisheries and Habitat Research conducting applied research focusing largely on seagrass restoration and ecology as well as derelict fishing gear issues. As Chief Scientist, Amy is responsible for developing and implementing the MDP’s Strategic Research Plan, overseeing our research portfolio, leading internal research projects, and overseeing external research projects funded by the MDP. Amy holds a B.S. in Biology from St. Bonaventure University and a M.S. in Marine Science – Biological Oceanography from the University of Puerto Rico-Mayagüez. She is currently pursuing her PhD (Zoology) at the University of Wisconsin-Madison.

Carlie Herring, NOAA Marine Debris Program Research Analyst.

Carlie Herring, Research Analyst

Carlie received her M.S. in Environmental Sciences in the Marine and Estuarine Science Program at Western Washington University with a thesis in ecological risk assessments. She completed a B.S. in Marine Sciences at the University of Maine, Orono. For her B.S., she conducted marine debris research, dealing specifically with plastics in the ocean. She also has experience as a marine science educator. As the Research Analyst, Carlie is responsible for overseeing research projects funded by the MDP, staying up-to-date on new marine debris research and literature, and is involved in the MDP’s Marine Debris Monitoring and Assessment Project.

We hope you enjoy learning about some of the great research initiatives that are going on and hope to see you at the Reddit “Ask Us Anything” on Thursday!

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Marine Debris Research: Ecological and Economic Assessment of Derelict Fishing Gear in the Chesapeake Bay

By: Amy Uhrin, Chief Scientist for the NOAA Marine Debris Program

The Chesapeake Bay blue crab fishery accounts for 50% of the United States blue crab harvest, and is worth about $80 million annually. It’s estimated that about 600,000 crab traps (also called “pots”) are actively fished on an annual basis in the Bay. Some crab pots become lost (derelict) when the pot’s buoy line becomes detached or cut, either by vessel propellers, faulty lines, or vandalism. Strong storms can also move pots from their original deployment location, making them difficult to relocate. In addition, pots may be abandoned, as has been observed at high rates in some regions of the Bay. Once lost, derelict pots can damage sensitive habitats and continue to capture blue crabs and other animals, often resulting in their death. To assess the ecological and economic impacts of derelict blue crab pots in the Chesapeake Bay, a diverse team of researchers from CSS-Dynamac, Inc.; Versar, Inc.; the Virginia Institute of Marine Science; and Global Science & Technology, Inc. recently completed a comprehensive Bay-wide assessment, funded by the NOAA Marine Debris Program.

A derelict drab trap.

Blue crabs are harvested using rigid, cube-shaped wire traps that are galvanized or vinyl-coated. Here, diamondback terrapins can be seen inside a standard pot. (Photo Credit: CCRM/VIMS)

This study estimates that some 145,000 derelict crab pots exist in the Chesapeake Bay, with 12-20% of actively-fished pots becoming lost each year. Not surprisingly, many derelict pots are found in areas of the Bay with heavy recreational and commercial boat traffic or fishing activity. These derelict pots kill over 3.3 million blue crabs annually. In addition, many other economically-important species can be impacted, such as white perch (3.5 million captured annually) and Atlantic croaker (3.6 million captured annually). Derelict pots thus “compete” with pots that are in active use —they catch or attract crabs that could otherwise be caught by active pots, and can therefore reduce commercial harvests.

Map of Chesapeake Bay with colors indicating density of derelict pots.

The predicted spatial distribution of derelict crab pot densities in Chesapeake Bay. (Photo Credit: CSS-Dynamac, Inc.; Versar, Inc.; Virginia Institute of Marine Science; and Global Science & Technology, Inc.)

Through statistical modeling, this study found that targeted derelict crab pot removal programs greatly increase the number of crabs caught by actively-fished pots, resulting in significant economic benefits for the fishery. The model estimated that derelict pot removals increased Bay-wide crab harvests by over 38 million pounds over a six-year period (2008 to 2014), amounting to $33.5 million in added revenue (in 2014 dollars). This study also found that pot removals are most effective when they focus on areas with intensive crab fishing activity.

This study also suggests management actions that may help in reducing the number of new derelict pots and their associated negative impacts. These include minimizing boat traffic in popular crabbing areas and educating boat operators about avoiding active crab pots, which would help reduce the number of cut buoy lines. Creating and maintaining derelict pot recovery programs, or incentivizing watermen to remove lost pots, would also help reduce the number of derelict pots in the Bay. In addition, outfitting crab pots with biodegradable “escape hatch” panels would reduce mortality of captured animals.

In addition to the Chesapeake Bay assessment, the team also created a Guiding Framework for derelict fishing gear assessments, which can be applied to other fisheries and/or regions interested in conducting similar studies. The final report for the Chesapeake Bay Assessment and the Guiding Framework document can be found on our website.