Oral Presentation Australian Freshwater Sciences Society Conference 2024

Polystyrene Microplastic as a Vector of Microcystin-LR in Eutrophic Freshwater and Estuarine Environments (112984)

Sadia Sharmin 1 , Siobhan Peters 2 , Anne Colville 1 , James Hitchcock 1 , David J. Booth 3 , David P. Bishop 2 , Simon M. Mitrovic 2
  1. Freshwater and Estuarine Research Group (FERG), School of Life Sciences, , University of Technology Sydney, PO Box 123, Broadway, Sydney, NSW, Australia
  2. Hyphenated Mass Spectrometry Laboratory (HyMaS), School of Mathematical and Physical Sciences, , University of Technology Sydney, PO Box 123, Broadway, Sydney, NSW, Australia
  3. Fish Ecology Lab, School of Life Sciences,, University of Technology Sydney, PO Box 123, Broadway, Sydney, NSW, Australia

Microplastics (MPs) and microcystins (MCs) are frequently reported in eutrophic environments, and their coexistence may have an additive ecological impact. However, the interaction of these stressors in aquatic systems is poorly understood. Thus, we performed a laboratory-based interaction experiment to explore the adsorption behaviour of MC-LR onto polystyrene MPs (PS-MPs) over time and to determine if there is any influence of different plastic sizes and salinities. Two particle size groups (180-500 µm and 700-1000 µm) PS-MPs were mixed with MC-LR lysate in two separate glass flasks containing 50 mL of either freshwater (salinity ≤ 0.001 g/L) or brackish water (salinity 16.00 g/L) and incubated at room temperature (25 °C) in an orbital shaker for 48 h. A 5 mL sample was taken at 0, 2, 4, 6, 8, 24, and 48 h, and PS-MPs were isolated through filtration. MC-LR concentration in a methanol extract of PS-MPs was measured using Triple Quadrupole LC-MS before calculating adsorption rate (%) and MC-LR (ng/g) onto PS-MPs. MC-LR adsorption rate (%) exhibited a degree of oscillation throughout MPs and MCs contact time with peaks in adsorption occurring after 4 and 6 hours in freshwater (2.02%) and brackish water (5%), respectively, and in smaller size PS-MPs. There was an interaction between salinity and particle size on MC-LR adsorption with adsorption higher on the smaller size fraction of PS-MPs under brackish water conditions. The results also showed that MC-LR could be only moderately adsorbed on PS-MPs (11 to 460 ng/g PS-MPs) with a relatively low adsorption rate of 0.1 to 5 %. This study provides evidence that PS-MPs have a limited potential as vectors of MC-LR in eutrophic freshwater and brackish environments.