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
09:00 AM
Size Dependence of Plastic Photochemical Lifetimes in Surface Waters (9365)
Primary Presenter: Aron Stubbins, Northeastern University (a.stubbins@northeastern.edu)
Microplastics are found floating on fresh and ocean waters. Sunlight-driven photochemistry can dissolve buoyant microplastics, removing them from the environment and producing dissolved organic carbon (DOC). However, it is unclear how photochemical lifetimes of plastics vary with particle size. We hypothesized that the increase in cross-sectional surface area to volume ratio as plastics decrease in size results in more rapid dissolution as smaller plastics receive a larger light dose per unit mass than larger plastics. To test this, samples of expanded polystyrene (EPS) and polypropylene (PP) spanning a range of sizes were irradiated floating on water in a solar simulator. A linear relationship between surface area to volume ratio and DOC accumulation rate was observed for EPS and a power relationship was observed for PP. Using these relationships, the photochemical lifetimes of plastics of different sizes were predicted. Results for macroplastics concur with general expectations that plastics take a long time to degrade, indicating that macroplastics greater than 10 cm should take almost 200 years to photochemically dissolve. However, at smaller sizes, plastics cease to meet these expectations, with 1 nm nanoplastics predicted to have lifetimes at the sea surface of 17 days for PP and 1 minute for EPS.
09:15 AM
TRACKING THE PHOTOOXIDATION PRODUCTS OF PRIMARY PLASTIC PELLETS (NURDLES) IN THE MARINE ENVIRONMENT (9080)
Primary Presenter: Xiangtao Jiang, University of Texas at Austin MSI (xtao.jiang@utexas.edu)
Marine plastic debris often undergoes photooxidation through sunlight exposure, potentially releasing substances that impact ecosystem health and carbon cycling. However, the photochemical modification of plastic polymers is still poorly understood. In this study, we investigated the photooxidation of two common plastic pellets (nurdles), polyethylene (PE) and polycarbonate (PC). Nurdles were exposed to simulated sunlight for 8 weeks, equivalent to 1.5 years of natural sunlight along the Texas coast, and their leachates were analyzed. FTIR confirmed surface oxidation of nurdles, showing oxygen incorporation into polymer chains as carbonyl and carboxyl groups. This exposure also facilitated the leaching of dissolved organic carbon (DOC) to seawater, PE nurdles released 18 times more DOC than PC nurdles. No nano-sized particles were detected through ultrafiltration (3k Da cut-off) or microscopy scanning. High-resolution mass spectrometry revealed an increase in molecular formulas within plastic-derived DOC by sunlight exposure. Over time, the oxygen-to-carbon ratio in PE-derived DOC increased, while the hydrogen-to-carbon ratio in PC-derived DOC decreased, indicating an enrichment of oxygenated compounds, likely due to an increase in carboxyl groups on nurdle surface during later stages of photooxidation, consistent with the FTIR results. Overall, these results demonstrate that sunlight exposure drives the release of plastic leachates, which consist of small molecules rather than nano-sized particles, offering new insights into the environmental fate of primary plastics.
09:30 AM
The Sum of the Parts: In situ degradation and fragmentation of plastic polymers in a forested and urban stream (9224)
Primary Presenter: Austin Gray, Virginia Tech (austindg@vt.edu)
Inland riverine systems are major conduits of organic materials to coastal systems, and they also transport plastics that enter the ocean. Plastic materials that pass-through streams are subjected to various degradation processes that facilitate their fragmentation into microplastics (MPs). Streams, therefore, are an influential but understudied landscape feature that affects the fate and transport of MPs. Here, we investigate the in-situ degradation of common plastic polymers (e.g., low-density polyethylene, polyethylene terephthalate, and polystyrene) and their fragmentation into MPs in urban and forested streams. We deployed plastic items and a natural biodegradable polymer (cellulose) into a stream habitat for 52 weeks. SEM-EDS analysis revealed biofilm formation on each plastic item, which was mainly composed of diatoms. We found that regardless of stream habitat type, polymers produced MPs in two weeks, with polystyrene having the highest fragmentation rate (8 particles/ week). We explored several degradation indices (carboxyl index, hydroxyl index, and vinyl index), which revealed that oxidation played a major role in plastic degradation over time. Lastly, we found that field-aged plastics can leach measurable levels of plastic-derived dissolved organic carbon, demonstrating plastics as a source of allochthonous carbon in streams that are relatively unaccounted for in carbon budget estimates. Our findings add to the knowledge gap regarding MP fragmentation in freshwater by providing real-time in situ data on the rate of polymer fragmentation and degradation in streams.
09:45 AM
Microplastics challenges microbial ecology and functions in aquatic systems (9044)
Primary Presenter: Hans-Peter Grossart, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) (hgrossart@igb-berlin.de)
Microplastics (MP) provide a unique and extensive surface for microbial colonization in aquatic ecosystems. The formation of microorganism-microplastic complexes, such as biofilms, maximizes the degradation of organic matter and horizontal gene transfer. In this context, MP affect the structure and function of microbial communities, which in turn render the physical and chemical fate of MP. This new paradigm generates challenges for microbiology, ecology, and ecotoxicology. Dispersal of MP is concomitant with that of their associated microorganisms and their mobile genetic elements, including antibiotic resistance genes, islands of pathogenicity, and diverse metabolic pathways. Functional changes in aquatic microbiomes can alter carbon metabolism and food webs, with unknown consequences on higher organisms or human microbiomes and hence health. Here, I examine a variety of effects of MP pollution from the microbial ecology perspective, whose repercussions on aquatic ecosystems begin to be unraveled.
10:00 AM
OCEANGOING PLASTICS AFFECT CHEMICAL SIGNALING AMONG HAB FORMING PHYTOPLANKTON (9767)
Primary Presenter: Remington Poulin, University of North Carolina Wilmington (poulinr@uncw.edu)
Phytoplankton, single-celled photosynthetic aquatic cells, are estimated to produce over 70% of the world's breathable oxygen, are involved in the microbial loop, and serve as the base of the oceanic food web. Many species of phytoplankton produce potent toxins that affect both marine and terrestrial organisms, bioaccumulate in seafood, and cause hundreds of millions of dollars of damage annually. In addition to these toxins, phytoplankton produce compounds that affect competitor physiology and behavior in a competition mechanism called allelopathy. Little is known of the identities of these allelochemicals, but their involvement in phytoplankton bloom dynamics has been hypothesized. Harmful algal blooms occur in coastal and riverine waterways and are subject to influxes of terrestrial contamination, including agricultural runoff, industrial/chemical waste, and importantly plastic waste. The impact of oceangoing plastics on toxin or allelochemical production in phytoplankton has yet to be addressed. The toxic dinoflagellate, Karlodinium veneficum is native to the waters of North Carolina and is known to produce a suite of toxins called karlotoxins. The effects of oceangoing plastics on allelopathy and karlotoxin production by K. veneficum were investigated in this study.
10:15 AM
Are MPs found in the Rio Grande/Bravo available to cause toxicity in zooplankton? (9641)
Primary Presenter: Judith Ríos Arana, Universidad Autónoma de Ciudad Juárez (jvraunicornio@gmail.com)
Due to the amount of plastic residues found in aquatic systems, various studies have been done to determine micro plastics (MPs) toxic effects in zooplankton organisms such as rotifers under laboratory conditions. However, not all MPs found in aquatic systems may cause toxicity, since not all can be ingested: rotifers from genus Brachionus ingest MPs of a 5-20µm size, while it is reported that Daphnia magna can ingest 300 and even 1400 µm MPs fibers. Based on this information we were interested to determine if the MPs found in the Rio Grande/Bravo could be ingested by rotifers or other zooplankton organisms. We quantified MPs, by fluorescence microscopy, from water samples collected at six sites along the Juarez, Chih. (Mexico) - El Paso, TX (USA) region, and determined MPs sizes by confocal microscopy. About 0.40 to 17 MPs/L were detected: sizes ranged from 24.83-4786.73 µm and 12.62-373.16 µm for fibers and fragments, respectively. Class interval for particle sizes was determined following Sturges’ Rule. It was found that fragments from three sites could be ingested by zooplankton organisms: Borderland (1.4 particles/L), Casa de Adobe (1.3 particles/L), and Altozano (0.3 particles/L). The information provided by this research gives us a hint of the real exposure of zooplankton to MPs.
SS12A - Identifying, measuring and responding to plastics in the aquatic environment
Description
Time: 9:00 AM
Date: 29/3/2025
Room: W208