Microplastics (MPs) are an escalating threat to marine ecosystems, steadily accumulating in the oceans and disrupting aquatic ecosystems. This study investigates the effects of MPs on microalgae activity of Skeletonema costatum, focusing on polystyrene (PS) and polymethyl methacrylate (PMMA). Microalgae cultures were exposed to 12.5 mg/L and 125 mg/L of MPs over 14 days. Preliminary tests revealed that adding Tween 20 inhibited algal growth, therefore it was excluded from further PS treatments. Without Tween 20, microalgae exposed to high concentrations of PMMA produced elevated chlorophyll a level, peaking at 975 mg/L compared to 384 mg/L in the control. Dissolved organic carbon (DOC) levels also increased across all treatments, indicating active microalgal metabolism. Additionally, this study explored the effects of light-aging on PMMA by suspending microplastics in Guillard's F2 medium and irradiating them with simulated solar radiation for 3 days using a solar simulator containing a 500 W ozone-free Xe lamp (SXUI501HQ, Ushio, Tokyo, Japan). Irradiated PMMA significantly inhibited microalgal growth, with chlorophyll a level dropping to 690 mg/L by day 8 in high concentrations, compared to 1010 mg/L in non-irradiated treatments. These findings suggest that while S. costatum can enhance growth in the presence of MPs, irradiation-induced surface changes reduce this potential, highlighting the need for further research into the long-term impact of light-aged MPs on microalgae and their role in coastal ecosystems.

Microplastic,Microalgae,Polymethyl methacrylate,Polystyrene