Plastic pollution has emerged as one of the foremost environmental contaminants in aquatic systems worldwide. Plastics are multifaceted, encompassing a variety of sizes (macro/meso: >5 mm, micro: 1 um – 5 mm, and nano: <1 um), shapes (fragments, fibers, beads) and chemistries (different polymers and chemical additive compositions). Plastic reaches the aquatic environment through various sources and, once there, is subject to natural weathering processes including physical abrasion, biodegradation, and photooxidation. As such, this aquatic contaminant presents significant and unique analytical challenges. These challenges have hindered the scientific community's ability to fully measure their extent and composition, or assess ultimate environmental impact. In ‘taking the pulse’ of aquatic environments, an understanding of current plastic pollution levels as well as best-methods for analyzing their future concentration, composition and toxicity is paramount. This session invites presenters to share research on a variety of plastic-related topics, including but not limited to: current plastic pollutions levels in different aquatic ecosystems; methods for improved plastic polymer/additive detection in aquatic matrices; methods to improve analysis of small micro- and nanoplastics and related chemical constituents; analysis of plastic fate and weathering in aquatic environments; novel techniques or perspectives for measuring plastic impacts and toxicity; studies elucidating the interactions between plastics and natural aquatic biogeochemical and ecological systems. All presenters are invited to highlight key research needs related to their work. In all, this session will provide attendees with an opportunity to discuss research gaps and identify opportunities for future research collaboration on plastic pollution in aquatic environments.
Lead Organizer: Meredith Seeley, Virginia Institute of Marine Science (VIMS), William & Mary (meseeley@vims.edu)
Co-organizers:
Zhanfei Liu, University of Texas Marine Science Institute (zhanfei.liu@utexas.edu)
Mara Walters, Virginia Institute of Marine Science (VIMS), William & Mary (mfwalters@vims.edu)
Presentations
06:00 PM
Citizen Science: Sampling and Identifying Microplastics and their Polymer-Types in Sandy Beaches (9416)
Primary Presenter: Andresa Lima, Northeastern University (oliveiratavareslim.a@northeastern.edu)
Microplastics are plastic pieces ranging from 1 µm to 5 mm, originating from industrial manufacture or plastic waste that degrades in the environment. Microplastics are found throughout the environment, including on beaches. Citizen scientist-led work helps collect data while engaging and educating a broader community in plastics research. However, current citizen science plastic sampling methods do not capture data about microplastic polymer types. This information is critical to understanding the origins, fate, and impact of microplastics in the environment. We adapted ROCHA's Guidelines for Sampling Microplastics on Sandy Beaches to provide an accessible citizen science method requiring few tools. To assess the method, sand was collected from three beaches in the metropolitan region of Salvador (Bahia, Brazil) following established protocols. Once sand and microplastics were separated in water, the buoyant microplastics were further separated into polyethylene, polypropylene, and expanded polystyrene. This polymer-specific separation was achieved through density difference using two household ethanol solutions. Fourier Transform Infrared Spectroscopy was used to independently determine the polymer type, verifying the use of our density separation method for accessible, rapid, and safe identification of polymer type by citizen scientists sampling microplastics on beaches and in other environments.
06:00 PM
BIOFILM-MEDIATED SEDIMENT TRAPPING INCREASES MICROPLASTIC DENSITY AND THEREBY ENHANCE VERTICAL FLUX OF PLASTICS IN THE OCEAN (9475)
Primary Presenter: Gregory Joern, Old Dominion University (gjoer001@odu.edu)
Our previous work showed that microbial organisms alone cannot induce sinking of buoyant microplastic particles larger than 40 µm. Here we experimentally examine whether biofilm-facilitated sediment accumulation can induce sinking in larger plastics. HDPE shopping bags and LDPE cling wrap were incubated in a tidal subestuary for 15 days during summer. The plastics were subsampled every two days to measure microbial biomass, photosynthetic pigments, silica, sediment mass, size, and plastic density using Percoll density gradient columns. Initially, the plastic bag material had a density of ~1.065 g/cm³, while the cling wrap was buoyant (<1.005 g/cm3). Both plastics showed minimal density change over the first 5 days but became strongly negatively buoyant (>1.1 g/cm³) by day 7. Silica accumulation was negligible until day 3, increased by day 9, and then remained invariable. Photosynthetic pigments followed a similar pattern, becoming detectable on day 3 and peaking between days 9-11. Sediment mass increased significantly from day 5, peaked on day 9, and then declined. Acid-soluble components of sediments (i.e., primarily carbonates) remained low until day 7, after which they increased steadily. In contrast, acid-insoluble sediments (i.e., primarily silica) trapped in the biofilm matrix were mostly responsible for the increased density of larger microplastics, facilitating their transport to deeper waters. The observed plateau in all variables at approximately day 7 into the incubation indicates that if plastics do not sink by then they may remain at the surface until denser, shell-bearing metazoans achieve dominance of the biofouling community.
06:00 PM
TECHNIQUE DEVELOPMENT: INVESTIGATING DRIVERS OF SPATIOTEMPORAL VARIANTION OF MICROPLASTICS IN FRESHWATER SYSTEMS (9181)
Primary Presenter: Riley Moran, University of North Carolina at Chapel Hill (andriley@ad.unc.edu)
Freshwater systems represent a critical conduit for microplastic transport across terrestrial systems and to marine ecosystems. Diverse extraction and quantification methods have been developed for riverine/lacustrine microplastics. Neuston net tows have been widely adopted for microplastic collection yet are ill-suited to capturing representative size ranges, thus significantly underestimate total microplastic burden. Neuston nets also pose challenges for controlling background contamination and collecting positive/negative controls. In the lab, identification via mass spectroscopy can be expensive and time consuming, which may substantially lower sample throughput and restrict spatiotemporal resolution, thereby limiting knowledge of processes that operate on short timescales (hours, days, or weeks). Many investigations have explored fluorescence microscopy as an alternative to mass spectroscopy. Here, we review refinements of methods for 2L grab-sample microplastic collection and identification via Nile red with novel sample florescence equipment. This method should offer rapid, semi-automated sample processing, and the ability to quantify microplastics >41 microns. Thus, this technique should offer more accurate estimates of total microplastic concentration, greater capacity for high spatiotemporal resolution studies, and the ability for labs without mass spectroscopy systems to investigate microplastic pollution. Additionally, we report preliminary data on biweekly spatiotemporal variations of microplastics (average 8.3 particles/L) in Jordan Lake and the Haw River, NC.
06:00 PM
Coastal convergence zones as microplastic hotspots: implications for marine life in the Seto Inland Sea (8776)
Primary Presenter: Masatoshi Nakakuni, Kagawa University (masatoshi.nakakuni@gmail.com)
This study examines microplastic (MP, 1–5 mm) densities in convergence zones in the Seto Inland Sea, comparing them to non-convergence zones. Convergence zones exhibited MP densities 40 to 300 times higher than non-convergence zones, with an extraordinary density of 3.7 ± 6.3 pieces m−3, similar to densities in known MP hotspots. Expanded polystyrene was the predominant polymer, varying seasonally and peaking in summer. Juvenile fish associated with driftweed in these zones face potential long-term MP exposure, up to four months. The massive MP accumulation in coastal convergence zones is comparable to accumulation zones in open ocean gyres, with significant implications for coastal marine life. However, these MPs are primarily autochthonous, suggesting potential management through local marine plastic waste initiatives. Our findings highlight the importance of considering small-scale oceanographic features in assessing marine plastic pollution and its ecological risks, emphasizing the need for targeted research on long-term impacts and formation mechanisms of these MP hotspots.
06:00 PM
THE BIOAVAILABILITY OF PHOTO-BLEACHED DISSOLVED ORGANIC CARBON FROM ENVIRONMENTALLY PREVALENT PLASTIC NURDLES IN MARINE WATERS (9222)
Primary Presenter: Kadee Loyd, University of Texas at Austin (kadee.loyd@utexas.edu)
Microplastics pose a significant threat to marine ecosystems, but due to their small size and vast dispersal, it is challenging to evaluate the environmental weathering and lifespan of the pollutants simply based on field samples. Through laboratory experiments, this study assessed the photodegradation of microplastics and the bioavailability of their weathering products in seawater. Nurdles of four polymer types – HDPE, PP, PET & PS – were exposed to four and eight weeks of simulated irradiation, equating to 0.75 and 1.5 years, respectively, of natural noon summer sun in south Texas. Irradiated samples were analyzed for oxidation and leachate production as dissolved organic carbon (DOC). FT-IR and SEM provided evidence of weathering for all four polymers, with HDPE exhibiting the most significant increases in its oxidative indices. PP nurdles produced the highest concentration of DOC, and this production, for all polymers, appeared to accelerate over time. Eight-week irradiated DOC was then inoculated with microbial consortium from the Gulf of Mexico coast for a 35-day period to observe biodegradation. While DOC degradation was high (75-95% for all polymers), bacterial cell growth was low, leading to growth efficiency values much lower than previous studies with natural DOM. This suggests that a small fraction of the microorganisms may have been responsible for plastic-DOC respiration; sequencing is ongoing and will be presented. Overall, this work provides insight into the longevity and fate of microplastics and plastic-derived substances in the ocean.
06:00 PM
EVALUATING THE WEATHERING AND TRANSPORT OF PLASTIC NURDLES ALONG THE NORTH- AND SOUTHWESTERN GULF OF MEXICO COASTS (9399)
Primary Presenter: Jordan Cisco, Ut Austin (graduate student) (j.cisco@utexas.edu)
Plastic nurdles, as small resin pellets, are a significant pollutant across the north- and southwestern Gulf of Mexico coasts from Texas to Yucatan Peninsula. In this study we conducted chemical analysis and physical oceanographic modelling to identify the sources, weathering, and movement pathways of nurdles on shorelines. Preliminary chemical data collected from over 70 sites from Houston to the Yucatán Peninsula (2021–2024) reveal distinct patterns in color, polymer type, and weathering status, which help to identify nurdle origins and their environmental exposure times. Polymer analysis through Fourier Transform Infrared Spectroscopy (FTIR) shows polyethylene (PE) as the dominant polymer across all the regions sampled, while color categorization reveals fresher white nurdles clustering around Texas sites and more weathered yellow nurdles in Mexico, suggesting that nurdles may have been mainly sourced from Texas and been continuously weathered during the transit to Mexico coasts. Weathering indices, including oxidation markers, further support these findings, showing increased degradation in nurdles collected farther from Texas. Physical oceanography modelling, including wave and current patterns, will be developed for nurdle movement, which will further refine our understanding of nurdle mobility throughout the Gulf and confirm or challenge our hypothesis that Texas is the primary source of this plastic pollution. This research not only highlights the regional differences in nurdle distribution but also offers crucial insights into the movement patterns of other types of microplastics in the Gulf of Mexico.
SS12P - Identifying, measuring and responding to plastics in the aquatic environment
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A