Do mixotrophic and phototrophic algae differ in their BPA removal capacity across a BPA gradient?

Chemical pollution poses an increasing threat to aquatic ecosystems, with bisphenol A (BPA) recognized as a widespread and hazardous contaminant. Although many microalgae can remove BPA, removal efficiency is strongly influenced by trophic strategy. This study directly compares BPA removal and physiological responses between a strictly autotrophic algae ( Scenedesmus sp.) and a mixotrophic algae ( Cryptomonas sp.). We exposed both taxa to an environmentally relevant BPA-gradient (0, 5, 10, 50, 100, and 1000 µg L ^− 1 ) over a seven-day incubation. Cell abundance, cumulative growth rate, maximal photochemical efficiency (ΦPSII), relative electron transport rate (rETR), chlorophyll a concentration, and respiration rate were measured to characterize metabolic responses. Metabolic flexibility was assessed using phototrophic performance (rETR:Chl a ) and specific respiration rate (sR). Scenedesmus sp. showed a consistent decline in rETR:Chl a across all BPA treatments, indicating impaired photosynthesis. In contrast, Cryptomonas sp. maintained stable phototrophic performance and increased sR, reflecting a shift toward heterotrophic energy pathways under stress. BPA removal further differentiated trophic modes: Cryptomonas sp. consistently removed 5–30% of BPA across concentrations, whereas Scenedesmus sp. exhibited reduced removal at higher BPA levels, consistent with toxicity. A positive relationship between respiration and BPA removal in Cryptomonas suggests partial metabolic utilization or detoxification. Overall, mixotrophic algae display functional advantages for BPA removal, highlighting trophic strategy as a key factor in algal bioremediation.