Arsenic biotransformation potential of marine phytoplankton under a salinity gradient

Abstract Salinity affects the biochemical and physiological activities of marine biota, including phytoplankton. The salinity tolerance and biotransformation capacity of phytoplankton depends on the species type and characteristics. In this study, we investigated the arsenic (As) biotransformation potential of three marine phytoplankton species, namely Prymnesium parvum, Oltmannsiellopsis viridis, and Eutreptiella gymnestica under a broad salinity gradient. Phytoplanktons were cultured in an f/2-based medium. Growth and As biotransformation potential were observed in As-poor and As-rich conditions in combination with phosphate (PO43−)-poor and PO43−-rich conditions, and different salinities (0–50‰). For all species, the highest cell concentrations were observed on day 14 of culture. Among the three species, O. viridis showed maximum growth, photosynthetic efficiency, As biotransformation, and total As accumulation ability under a broad range of salinities (≥5‰ to ≤45‰). However, As biotransformation and other physiological activities decreased for all the phytoplankton species at ≤5‰ and ≥45‰. Phytoplankton growth and As biotransformation potential was significantly influenced by salinity and by the availability of As and PO43− in the culture medium. A conceptual model of salinity effects on As uptake and biotransformation in the three marine phytoplankton species is proposed based on the findings of this study.