Rocha Giseli Swerts, Melão Maria Graça Gama
Universitat Rovira i Virgili, Escola Tècnica Superior d'Enginyeria Química, Departament d'Enginyeria Química, Av. Països Catalans, 26, 43007, Tarragona, Spain.
Departamento de Hidrobiologia, Centro de Ciências Biológicas e da Saúde (CCBS), Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luís, Km 235, CEP, 13565-905, São Carlos, SP, Brazil.
Environ Pollut. 2024 Jan 15;341:122998. doi: 10.1016/j.envpol.2023.122998. Epub 2023 Nov 21.
Phosphorus (P; macronutrient) and cobalt (Co; micronutrient) are essential for algal healthy metabolism. While P provides energy, Co is a co-factor of several enzymes and component of B12 vitamin. However, in concentrations higher or lower than required, P and Co alter algal metabolism, impacting physiological processes (e.g., growth and photosynthesis), usually in a harmful way. In the environment, algae are exposed to multiple stressors simultaneously and studies evaluating the algal response to the combination of macronutrient limitation and micronutrient excess are still scarce. We assessed the effects of P limitation and Co excess, isolated and combined, in Raphidocelis subcapitata (Chlorophyceae), in terms of growth, pigments production, and photosynthetic parameters. Except for the photochemical quenching (qP) and the efficiency in light capture (α) under P limitation, all parameters were affected by both stressors, isolated and combined. Under P limitation, chlorophyll a was the most sensitive parameter; while excess of Co affected most the photoprotective mechanisms of algae, altering the non-photochemical quenchings qN and NPQ, influencing the light use and dissipation of heat by algae. The combination of two stressors resulted in a significant decrease in algal growth, with synergistic responses in growth and pigments production, and antagonism in the photosynthetic parameters. We suggest that algal metabolism was altered during P limitation acclimation and the excess of Co was used in a beneficial way by P-limited algae in photosynthesis, resulting in the well-functioning of the photosynthetic apparatus in the combination of both stressors. However, more studies are needed to understand which mechanisms are involved in this adaptation which resulted in antagonism in photosynthetic processes and synergism in growth and pigments production.
磷（P；大量营养素）和钴（Co；微量营养素）对藻类的健康代谢至关重要。磷提供能量，而钴是几种酶的辅助因子和维生素B12的组成成分。然而，当磷和钴的浓度高于或低于所需水平时，它们会改变藻类的代谢，通常以有害的方式影响生理过程（如生长和光合作用）。在环境中，藻类同时面临多种压力源，而评估藻类对大量营养素限制和微量营养素过量组合的反应的研究仍然很少。我们评估了磷限制和钴过量单独及联合作用对亚心形扁藻（绿藻纲）在生长、色素产生和光合参数方面的影响。除了磷限制下的光化学猝灭（qP）和光捕获效率（α）外，所有参数都受到单独和联合的两种压力源的影响。在磷限制下，叶绿素a是最敏感的参数；而钴过量对藻类的光保护机制影响最大，改变了非光化学猝灭qN和NPQ，影响了藻类的光利用和热量耗散。两种压力源的组合导致藻类生长显著下降，在生长和色素产生方面有协同反应，而在光合参数方面有拮抗作用。我们认为，在磷限制适应过程中藻类代谢发生了改变，磷限制的藻类在光合作用中以有益的方式利用了过量的钴，导致在两种压力源组合下光合装置功能良好。然而，需要更多的研究来了解这种适应涉及哪些机制，这种适应导致了光合过程中的拮抗作用以及生长和色素产生中的协同作用。
