Biofilm Formation on Polyethylene Microplastics Affects Brevetoxin Adsorption and Desorption

Microplastics can serve as sites for microbial attachment, however their role in facilitating biotoxin entry into marine food webs remains poorly understood. This study quantified the adsorption and desorption kinetics of brevetoxin 3 (PbTx-3), a neurotoxin produced by the dinoflagellate Karenia brevis, on polyethylene (PE) surfaces in relation to the presence of biofilms using radiolabeled ³H-PbTx-3. It was hypothesized that the presence of biofilms would enhance toxin retention on PE. Contrary to this hypothesis, results revealed significantly reduced adsorption of brevetoxin on biofilm-coated PE (0.035 ± 0.007 nmol mg^-1, p < 0.001) compared to virgin PE (0.59 ± 0.076 nmol mg^-1). Furthermore, toxin desorption from biofilm-coated PE occurred rapidly, with less than 20% activity remaining after 24 h, whereas virgin PE retained over 80% activity over the same period. Complete toxin depuration was not observed within one week under either condition. These findings demonstrate that biofilms not only reduce brevetoxin adsorption on PE but also accelerate desorption. Further research is needed to elucidate the broader ecological and health implications of microplastic-mediated biotoxin transport, albeit the results of this study suggest that biofilm-coated PE likely plays a minor role as vector for biotoxins in marine food webs, at least compared to its virgin counterpart.