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Impact of polystyrene microbeads on the biomass, biochemical constituents, and pigment levels of marine diatoms

Journal of Earth System Science 2026
Velusamy Gayathri, Ashok Kumar Kavya, A. Gowthami, P. Santhanam, P. Santhanam, Subramanian Radhakrishnan, Mathan Ramesh, Thirunavukkarasu Muralisankar

Summary

Exposure to polystyrene microbeads caused significant declines in biomass, pigments, protein, and carbohydrates in two marine diatom species over 30 days, while also triggering surface changes in the plastic suggesting early-stage biodegradation by the diatoms. Because diatoms form the base of marine food webs and drive ocean carbon fixation, microplastic-induced suppression of their growth has cascading implications for ocean ecosystem productivity.

Polymers

Microplastic pollution in the marine environment poses a significant threat to biotic compartments. In this study, we evaluated the impact of polystyrene (PS) microbeads on the biomass, pigment levels, and biochemical constituents of two marine diatoms, Amphora sp. and Navicula sp. Moreover, the hydrophilicity of PS microbeads was assessed using contact angle measurements to determine the biodegradation potential of these diatoms. Marine diatoms were exposed to PS microbeads at a concentration of 200 mg/150 mL of culture medium separately for 30 days, while untreated diatoms served as respective controls. The results showed a significant decrease (p < 0.05) in biomass, pigments, protein, and carbohydrate levels in both Amphora sp. and Navicula sp., indicating their vulnerability to PS microbeads. However, an increase in lipid content in both species suggests a defence mechanism in response to PS exposure. Furthermore, contact angle measurements revealed surface changes in PS microbeads from hydrophobic to hydrophilic, indicating the initiation of the biodegradation process by the marine diatoms.

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