THE BIOAVAILABILITY OF PHOTO-BLEACHED DISSOLVED ORGANIC CARBON FROM ENVIRONMENTALLY PREVALENT PLASTIC NURDLES IN MARINE WATERS

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.

Presentation Preference: Poster

Primary Presenter: Kadee Loyd, University of Texas at Austin (kadee.loyd@utexas.edu)

Authors:

Kadee Loyd, The University of Texas at Austin - Marine Science Institute  (kadee.loyd@utexas.edu)

Xiangtao Jiang, The University of Texas at Austin - Marine Science Institute  (xtao.jiang@utexas.edu)

Kaijun Lu, The University of Texas at Austin - Marine Science Institute  (kaijun.lu@utexas.edu)

Kasia Dinkeloo, The University of Texas at Austin  (kdinkeloo@utexas.edu)

Zhanfei Liu, The University of Texas - Marine Science Institute  (zhanfei.liu@utexas.edu)