Abstract
Introduction The impact of ocean acidification (OA) and nanoplastics (NPs) on harmful algal blooms (HAB) has emerged as a major global concern. However, the combined effects of OA and NPs on the HAB species are poorly understood. Methods In this study, dinoflagellate Prorocentrum donghaiense , a typical HAB species, was exposed to varying concentrations of NPs (108.15 ± 8.52 nm) (0, 5, 10, and 15 mg L −1 ) and CO 2 (low CO 2 : 417 ppm, pH: 8.00 and high CO 2 : 1045 ppm, pH: 7.73) for seven days to investigate the combined effects of OA and NPs. Results and discussion The findings revealed that NPs inhibited the growth of P. donghaiense by inducing oxidative stress, as indicated by elevated malondialdehyde (MDA) content and decreased carotenoid/chlorophyll-a ratio, even though photochemical efficiency (φ P0 , ψ 0 , and φ E0 ), rETR max and α were enhanced in response to NPs stress. However, OA promoted the growth and alleviated the adverse effects of NPs on P. donghaiense by increasing photochemical efficiency (φ P0 , ψ 0 , and φ E0 ) and energy flux (RC/CS 0 , TR 0 /CS 0 , ET 0 /CS 0 ) and enhancing the antioxidant ability (increased superoxide dismutase, and decreased MDA). P. donghaiense showed enhanced tolerance to NPs under simulated OA conditions. These findings enhance our knowledge of the HAB species response to NPs pollution under future OA scenarios.