Senior Capstone

This research study explores the potential seasonality of microplastic distribution along United States coastlines. Microplastics, defined as plastic particles between 1 mm and 5 mm in size, primarily result from the degradation of larger plastic items, with additional contributions from spilled nurdles, the small plastic pellets used in manufacturing. Our study investigates how the density of microplastics varies across different seasons, noting higher concentrations during dry seasons such as Fall and Winter, possibly due to stronger ocean currents and reduced rainfall. This pattern aligns with findings from studies in other regions, suggesting a broader correlation between microplastic density and seasonal variations.

Despite the observed trends, the study acknowledges limitations due to data collection methods and regional factors that could influence outcomes. Research by Garnett et al. (2021) and Callies et al. (2015) suggests that microplastic behavior may be affected by solubility in saline water and seasonal ocean currents. The health impacts of microplastics are also discussed, highlighting potential risks for marine life and humans, though more research is needed to fully understand the extent of these effects.

Our findings highlight the need for comprehensive and/or interdisciplinary studies on microplastic pollution, focusing on various contributing factors and their impact on marine ecosystems and human health. Recommendations include targeted cleanup efforts during high-density seasons and further investigation into the sources of microplastic pollution, with an emphasis on improving data collection methods and exploring effective mitigation strategies.

How do seasonal weather patterns influence microplastic density along the US coastline? If a correlation does exist, or seems to exist, what steps can be taken to minimize potential environmental impacts and protect human-related activities?

Given the outcomes in international studies examining the seasonal effects on microplastic density, we predict the discovery of similar trends in the United States. This would support the hypothesis that seasonal shifts, especially during the Fall, are closely linked to variations in microplastic density and distribution across different regions.

Due to the limitations of our research group's time, travel capabilities, and budget, we will base our research project on data from the 2020 study by University of Texas Marine Science Institute, in collaboration with NOAA (National Oceanic and Atmospheric Association) and the non-profit group Nurdle Patrol. The study involved citizen scientists conducting monthly surveys on beaches to gather information about nurdles (small plastic pellets), with data compiled from 2018 to 2022. Our team will use this data to study the relationship between seasonal shifts and microplastic density.

While Nurdle Patrol's data spans several years and covers various US regions, we narrowed our focus to six U.S. locations:

• Houston, TX

• Bandon, OR

• Charleston, SC

• Long Beach, CA

• New Orleans, LA

• Prudence Park, RI

The data areas were chosen so that there were two locations along the West, South, and East United States coastlines. These locations offer a range of geographical and climate profiles as well, allowing us to examine seasonal effects on microplastic distribution while minimizing regional bias.

The data, publicly available via NOAA, is presented in terms of nurdles collected in 10-minute beach patrols. Citizen scientists are instructed to patrol their local beaches once a month, at the same day and time every month, collecting nurdles below the tide lines for ten minutes. The data is then categorized by the number of nurdles found, with "Very High" representing 200+ nurdles, "High" indicating 40-200, "Medium" 2-40, "Low" 1-2, and "Very Low" 0. Data collection has a potential margin of error due to human error. 

The data was compiled into spreadsheets to create charts and graphs that visualize microplastic density by season for each location. To ensure consistency, we will define seasons by the approximate equinox and solstice dates: Spring (March 19-21), Summer (June 20-22), Fall (September 21-24), and Winter (December 20-23). Using the density and seasonal categories created, the data was organized into pie charts to illustrate the distribution of microplastic density values for each season and across different locations. Combined data across the months collected from December 2018 to May 2022 was organized into categories for the bar chart showcasing the “High” and “Very High” microplastic density per location.

Ultimately, this analysis aims to determine whether seasonal changes correlate with variations in microplastic density. If a strong correlation emerges between high and low-density values across seasons, we will explore potential reasons behind these trends and discuss any recommended actions to reduce the impact of microplastics on the environment. If results are inconclusive, the lower density data might still provide insights into the seasonal effects on microplastic distribution.

The provided data illustrates the quantity of microplastics found by the Nurdle Patrol across various conditions from 2018 to 2022. Six locations were monitored, and the data was organized by season, resulting in pie charts representing the proportion of times a certain number of microplastics was found at each location during a specific season. Additionally, four pie charts display seasonal percentages, while a bar chart demonstrates data density from each location, focusing on "Very High" and "High" density data that contributed to research conclusions. Due to reliance on volunteer data, some months may lack coverage. It's noted that Fall and Winter are typically "dry" seasons, while Spring and Summer are "wet."

Despite human activity, microplastic levels are generally low, with the majority falling into the "Very Low" category. No "High" or "Very High" data points were observed at one location, making it an outlier. New Orleans exhibits the highest concentration of "Very High" and "High" data points, likely due to its high population density and frequent large-scale events. Long Beach, CA, mostly reports "Medium" data points. Houston, Texas, has the most "High" quantity days, while Charleston, SC, has the most data points. Bandon, Oregon, and Charleston, SC, have similar "High" and "Medium" levels, with Bandon showing a higher proportion of "Very High" readings.

Seasonal analysis reveals Spring as the second-highest for "Very High" and "High" data points. Summer has the most "Very High" counts but also the largest "Very Low" percentage. Fall exhibits the most "High" and "Very High" counts, indicating the highest microplastic density. Winter shares similarities with Spring but with fewer "Very High" days. Overall, most days across all seasons and locations show "High" quantities of nurdles, emphasizing the low chance of experiencing no microplastics along coastlines. Houston and Charleston contribute significantly to "Very High" and "High" data points, potentially due to population size and citizen scientist presence.

In conclusion, microplastic presence varies by season and location, with Winter and Fall recording the most "Very High" and "High" levels, suggesting seasonal environmental factors influence microplastic accumulation. Monitoring seasonal trends is vital for understanding sources and impacts.

The data analysis indicates a notable increase in microplastic density and distribution during Fall, with 36.7% of data points falling into "Very High" or "High" categories. Winter follows with an additional 28% of observed days. In contrast, Summer and Spring show lower percentages, at 16.19% and 19.2% respectively, suggesting a clear seasonal pattern of higher microplastic densities during dry seasons (Fall and Winter) compared to wet seasons (Summer and Spring). Dry seasons account for 64.7% of all "Very High" and "High" readings across six locations.

Figure 13 highlights Charleston and Houston as major contributors to "Very High" and "High" data points. The study concludes distinct seasonal patterns in microplastic density along U.S. coastlines, suggesting ocean currents, possibly driven by submesoscale turbulence, could be a contributing factor, pushing microplastics toward shorelines where they accumulate. Human activities, such as tourism and beach events, might also influence seasonality, though not included in this research, warranting further investigation. 

While ocean temperature changes could impact microplastic density by altering salinity levels, the study suggests no direct evidence linking Arctic sea ice enrichment with microplastic density in U.S. coastal waters. Further research is needed to examine changing salinity's impact on microplastic density. Aligning with Gao's 2021 study on Chinese oceans, both studies observe higher microplastic densities during dry seasons compared to wet seasons, validating the hypothesis that dry seasons elevate microplastic density in U.S. coastal waters.

Based on our analysis, several solutions could address the problem of microplastics in oceans and on beaches. As noted earlier, these microplastics inevitably find their way into the food web and ultimately into the human body. Current technology is inadequate for effectively cleaning up microplastic pollution from water without damaging ecosystems. Manually sifting through ocean water to remove microplastics risks capturing and killing marine organisms, while larger filter holes might miss many microplastics. This makes policies focused on cleaning microplastics impractical until technology advances.

Instead, policies that target the production and transportation of plastic products are more likely to successfully curb the rapid spread of microplastics in ecosystems. Specifically, limiting the production of nurdles and closely monitoring their manufacturing, transportation, and use would significantly reduce the risk of accidental spills. Policies should also treat nurdle spills with the same urgency as oil spills. While measures to reduce plastic consumption, such as limiting plastic straws, drink lids, and disposable plastic bags, may indirectly help with microplastic pollution, they do not directly prevent nurdles from entering the environment. Our data suggests that most microplastics in ocean ecosystems originate from mishandling during the production, transportation, and waste processing of nurdles. Therefore, addressing potential mishandling or spillage throughout the nurdle’s life cycle stages is crucial in mitigating the spread of microplastics.

While the NOAA data strongly suggests a relationship between seasonality and coastal microplastic distribution, it does not provide definitive proof backed by statistical analysis for our study’s purposes. The accuracy of the results has a strong likelihood of being compromised due to the Nurdle Patrol, which relies on citizen scientists collecting data over a short four-year timeframe. This limitation of human error, as well as the absence of other reliable data sources on microplastics in ocean waters, is significant enough to impact our research methodology. Future research surrounding coastal microplastics would benefit from experiments focused on identifying the types of short-chain and long-chain plastics found in each season, for example, to better understand their solubility in saline water and how it impacts microplastic distributions. Additional experiments should also be conducted on a smaller scale, ensuring more precise data collection, rather than depending on the broader, erroneous-prone method employed by the Nurdle Patrol. The primary concern with the method used by the Nurdle Patrol organization is the potential for human error when manually collecting nurdles within a ten-minute timeframe, which may result in data that lacks consistency and accuracy.

In conclusion, while our research hints at a correlation between the dry seasons and higher distribution and density of microplastics along the US coast, this data is not sufficient to draw firm conclusions. However, microplastic cleanup is advised, since coastal areas tend to be attractive areas with large amounts of visitors per year. We recommend further studies to gain a more defined understanding of microplastic behavior, focusing specifically on human health risk and environmental impact.

All Capstone Project References/Citations

Marine Microplastic Concentrations - Interactive Map

About the Citizen Science Project - Nurdle Patrol