Modeling Global Suitable Areas for a Harmful Algal Bloom Species, Phaeocystis globosa, under Climate Change Scenarios Using Maxent

Phaeocystis globosa is a globally distributed species recognized as a significant contributor to harmful algal blooms (HABs) across different regions. Based on the maximum entropy (Maxent) approach, this study aimed to predict shifts in the ecological niche in these regions under various climate change scenarios with focus on the current, mid-century (2040s), and late-century (2090s) suitable areas. A comprehensive dataset of 13 environmental factors was screened using the jackknife techniques to assess variable importance and the Spearman correlation analysis to identify the key drivers. After screening the environmental factors, the Maxent model was constructed and calibrated using P. globosa geographic distribution data, and the model performance was then evaluated through validation techniques. Iron minimum (Ir.Min), mean primary production (Pr.Mean), and nitrate minimum (N.Min) were identified as the primary environmental factors influencing the distribution of suitable areas for P. globosa. Under current climate conditions, the global distribution of P. globosa can be classified into high-suitability areas (1.70%), medium-suitability areas (2.69%), and low-suitability areas (31.26%). In the future, the overall suitable area is expected to shift westward and significantly expand. While the low-suitability areas are projected to remain relatively unchanged, the high- and medium-suitability areas are expected to expand by approximately 23.50 and 3.97%, respectively. The main environmental factors influencing the current global distribution of P. globosa are Ir.Min, Pr.Mean, and N.Min. Highly suitable areas for P. globosa are located in marine regions of many industrialized countries. Under future climate conditions, the number of suitable areas is expected to increase dramatically in response to rising CO2 concentrations, and the centroid of these areas is predicted to shift significantly westward. Therefore, it is crucial to focus on monitoring and managing highly suitable areas for P. globosa.