Slomka Shai, Verspagen Jolanda M H, Huisman Jef, Wilken Susanne
Department of Freshwater and Marine Ecology (FAME), Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Science Park 904, Amsterdam, 1098 XH, The Netherlands.
ISME Commun. 2025 Apr 18;5(1):ycaf064. doi: 10.1093/ismeco/ycaf064. eCollection 2025 Jan.
Marine phytoplankton are facing increasing dissolved CO concentrations and ocean acidification caused by anthropogenic CO emissions. Mixotrophic organisms are capable of both photosynthesis and phagotrophy of prey and are found across almost all phytoplankton taxa and diverse environments. Yet, we know very little about how mixotrophs respond to ocean acidification. Therefore, we studied responses to simulated ocean acidification in three strains of the mixotrophic chrysophyte (CCMP1391, CCMP2951, and CCMP1393). After acclimatization of the strains to treatment with high-CO (1000 ppm, pH 7.9) and low-CO concentrations (350 ppm, pH 8.3), strains CCMP1393 and CCMP2951 both exhibited higher growth rates in response to the high-CO treatment. In terms of the balance between phototrophic and heterotrophic metabolism, diverse responses were observed. In response to the high-CO treatment, strain CCMP1393 showed increased photosynthetic carbon fixation rates, while CCMP1391 exhibited higher grazing rates, and CCMP2951 did not show significant alteration of either rate. Hence, all three strains responded to ocean acidification, but in different ways. The variability in their responses highlights the need for better understanding of the functional diversity among mixotrophs in order to enhance predictive understanding of their contributions to global carbon cycling in the future.
海洋浮游植物正面临着因人为碳排放导致的溶解态二氧化碳浓度上升和海洋酸化问题。混合营养生物既能进行光合作用,又能捕食猎物,几乎在所有浮游植物类群和不同环境中都能找到。然而,我们对混合营养生物如何应对海洋酸化却知之甚少。因此,我们研究了三种混合营养金藻(CCMP1391、CCMP2951和CCMP1393)对模拟海洋酸化的反应。在将这些菌株驯化至高二氧化碳(1000 ppm,pH 7.9)和低二氧化碳浓度(350 ppm,pH 8.3)处理后,CCMP1393和CCMP2951菌株在高二氧化碳处理下均表现出更高的生长速率。在光合营养和异养代谢之间的平衡方面,观察到了不同的反应。在高二氧化碳处理下,CCMP1393菌株的光合碳固定率增加,而CCMP1391表现出更高的摄食率,CCMP2951的这两种速率均未显示出显著变化。因此,所有这三种菌株都对海洋酸化做出了反应,但方式不同。它们反应的变异性凸显了更好地了解混合营养生物之间功能多样性的必要性,以便增强对它们未来对全球碳循环贡献的预测性理解。