Pseudo-nitzschia encompasses certain species and strains capable of producing the neurotoxin domoic acid (DA). These organisms frequently form harmful algal blooms, posing significant risks to marine ecosystems and human health. With increasing nutrient inputs into marine environments and rising temperatures due to global warming, Pseudo-nitzschia are experiencing a shifting growth regime. However, our understanding of the thermal responses of toxic and non-toxic Pseudo-nitzschia strains under varying nutrient conditions remains unclear. To address this gap, we compared thermal performance curves and associated thermal traits under nitrogen-replete and nitrogen-limited conditions for two toxic and two non-toxic strains of P. cuspidata. Our results revealed that in nitrogen-replete environments, toxic strains displayed greater temperature sensitivity (E_a), lower optimal temperatures (T_opt), and comparable maximum growth rates (μ_max) relative to non-toxic strains. This suggests that toxic Pseudo-nitzschia respond more rapidly to rising temperatures but exhibit lower thermal tolerance. Furthermore, nitrogen limitation markedly decreased T_opt and μ_max for both toxic and non-toxic strains, with a more pronounced reduction in μ_max for toxic P. cuspidata. The contrasting thermal responses of toxic and non-toxic P. cuspidata may be linked to DA production in toxic strains, as well as their significantly enhanced nitrogen and respiratory metabolism under high-temperature, nitrogen-limited conditions. These findings provide novel insights into the future population dynamics of both toxic and non-toxic Pseudo-nitzschia in regional marine ecosystems.
 

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