Ocean acidification (OA) fundamentally reshapes the chemical landscape of coastal waters, yet the mechanistic basis for the resilience and metabolic adaptation of the bloom-forming alga Phaeocystis globosa remains poorly understood. By disentangling the individual and interactive effects of elevated pCO2 and reduced pH, this study shows that P. globosa exhibits distinct physiological and metabolic responses to these stressors. Reduced pH emerged as the stronger physiological constraint, significantly inhibiting growth, whereas the reduction in relative maximum electron transport rate (rETRmax) was not statistically significant; these responses override the potential benefits of CO2 fertilization. Transcriptomic profiling revealed diver-specific reprogramming of carbon and nitrogen metabolism: reduced pH induced coordinated down-regulation, elevated pCO2 coordinated up-regulation, and combined stress opposing trends. Key nitrogen genes (NR, NiR, GS) shifted phase-dependently. The absence of detectable CPS and OTC transcripts, together with multiple pathways potentially contributing to endogenous ammonium supply, points to a potentially truncated urea cycle and flexible nitrogen utilization. As an exploratory transcriptomic analysis, these results suggest that P. globosa may possess ecological resilience under future acidification.
Zhou Y., Lv Y., Li X., Yu Z. & Yu Z., 2026. Uncoupling the effects of pH and pCO2: how Phaeocystis globosa adapts its nitrogen assimilation to an acidifying ocean. Research Square. Article.
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