Photocatalytic Characteristic of Semiconducting Mineral Anatase and Microbial Community in the Marine Euphotic Zone of the Beibu Gulf, South China Sea

This study has thoroughly uncovered the characteristics of the marine euphotic zone system in the Beibu Gulf, featuring adjacent semiconducting minerals and electrochemically active microbes, via mineralogical characterization, photoelectrochemical measurements, and microbiological analysis techniques. Notably, results of Raman and ESEM with EDS indicated that anatase, the semiconducting mineral with prominent photocatalytic performance, exists in large quantities in the Beibu Gulf. Photoelectrochemical measurements tested photoelectric response and redox activity of suspended particulate minerals, demonstrating the suspended particulates dominated by titanium and iron oxide semiconducting minerals presented excellent photo-response property and distinct photoelectric catalytic potential under visible light irradiation. Its significant property of photoelectric response with 110.483% increment ratio of the average photocurrent density relative to the dark current density. 16S amplicon sequence analysis revealed that the euphotic zone was dominated by Proteobacteria, Actinobacteria, and Cyanobacteria at the phylum level, and by Synechococcus CC9902, Cyanobium PCC-6307 and unclassified Ilumatobacteraceae at the genus level. Halomonas (0.2–1.2%), Vibrio (0.7–1.8%), and Nautella (0.1–1.1%), closely related to semiconducting minerals reduction reaction, were also presented in YL and RGS samples of the Beibu Gulf. This work firstly revealed that the neglected characteristics of the marine euphotic zone system in the Beibu Gulf of the South China Sea, which is an important natural ecosystem for microorganisms to uptake energy sources. It will provide a new perspective for further research on novel ways for microorganisms to acquire energy sources through semiconducting minerals in the marine euphotic zone system.