Effects of Microplastics Exposure on the Feeding of the Heterotrophic Dinoflagellate Species Noctiluca scintillans

The pollution effects of microplastics (MPs) on the feeding of the heterotrophic dinoflagellate species, Noctiluca scintillans, was investigated. The algal prey species, Dunaliella tertiolecta, was fed to N. scintillans and fluorescent microspheres were used as surrogates for microplastic wastes. Holling's type II functional response model revealed that N. scintillans could reach a maximum prey ingestion rate of 2,242 cells grazer⁻¹ d⁻¹ (~ 214 ngC grazer⁻¹ d⁻¹) under normal conditions. In exposure to a mixture of prey and MPs, N. scintillans showed mean prey ingestion rates of 1,078 and 820 cells grazer⁻¹ d⁻¹ at Prey:MP ratios of 500:1 (i.e., ~ 88 MP particles mL⁻¹) and 5000:1 (i.e., ~ 8 MP particles mL⁻¹), respectively. The number of N. scintillans cells with ingested MP particles increased with decreasing Prey:MP ratios (200:1, 50:1, 10:1, and 1:1), indicating the non-selective feeding between the algal prey and MP particles. This study is the first one to investigate the effects of microplastic pollution on this common red-tide-causing dinoflagellate species. We urge that more research is needed to reveal the ecological implications of microplastic pollution in the marine ecosystems.