Jiangsu Key Laboratory for Biodiversity and Biotechnology, School of Biological Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China.
Jiangsu Key Laboratory for Biodiversity and Biotechnology, School of Biological Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China.
Harmful Algae. 2022 Aug;117:102293. doi: 10.1016/j.hal.2022.102293. Epub 2022 Jul 30.
In eutrophic freshwaters, Microcystis usually becomes dominant in phytoplankton communities due to the synergistic effects of its special eco-physiological traits and environmental factors. Colonial morphology can protect Microcystis from zooplankton grazing, which indirectly favors Microcystis to outcompete other phytoplankton, although the colonial form is not conducive to the absorption of nutrients. Moreover, unicellular Microcystis usually has competitive advantages over other phytoplankton due to its efficient absorption capacity for nutrients and releasing microcystins. However, the consequence of direct competition between toxic colonial Microcystis and green algae without external grazing pressure still remained unknown. In this study, the competition between toxic colonial Microcystis aeruginosa and a common green alga Scenedesmus obliquus was explored. Results showed that: (1) colonial M. aeruginosa had a higher requirement for key macro-nutrient phosphorus than S. obliquus, and thus its population declined and was replaced by S. obliquus eventually; (2) microcystins released by colonial M. aeruginosa inhibited the photosynthetic activity and growth of S. obliquus at early stage of the competition; (3) the photosynthetic potential of colonial M. aeruginosa was stimulated in response to the competitive stress from S. obliquus, although the population of colonial M. aeruginosa declined eventually; (4) microcystin production of colonial M. aeruginosa was enhanced by phosphorus limitation due to S. obliquus competition and was positively related to photosynthetic potential of colonial M. aeruginosa. These results indicated that, in the absence of complex natural environment, colonial Microcystis cannot outcompete Scenedesmus in a pure competition, although microcystins can play a favorable role in the competition, which clarified the opposite role of colonies and microcystins in the competition of colonial Microcystis against other phytoplankton.
在富营养化的淡水中，由于特殊的生态生理特性和环境因素的协同作用，微囊藻通常在浮游植物群落中占优势。群体形态可以保护微囊藻免受浮游动物的摄食，这间接有利于微囊藻与其他浮游植物竞争，尽管群体形式不利于营养物质的吸收。此外，由于微囊藻对营养物质具有高效的吸收能力并释放微囊藻毒素，单细胞微囊藻通常比其他浮游植物具有竞争优势。然而，在没有外部摄食压力的情况下，有毒群体微囊藻与绿藻之间直接竞争的后果仍然未知。在这项研究中，探讨了有毒群体微囊藻和常见绿藻斜生栅藻之间的竞争。结果表明：（1）群体微囊藻对关键宏量营养磷的需求高于斜生栅藻，因此其种群下降并最终被斜生栅藻取代；（2）群体微囊藻释放的微囊藻毒素在竞争的早期抑制了斜生栅藻的光合作用和生长；（3）尽管群体微囊藻的种群最终下降，但群体微囊藻的光合作用潜力受到斜生栅藻竞争的刺激；（4）由于斜生栅藻的竞争和磷限制，群体微囊藻的微囊藻毒素产生增强，并与群体微囊藻的光合作用潜力呈正相关。这些结果表明，在没有复杂自然环境的情况下，群体微囊藻在纯竞争中无法胜过斜生栅藻，尽管微囊藻毒素在竞争中可以发挥有利作用，但这阐明了群体和微囊藻毒素在群体微囊藻与其他浮游植物竞争中的相反作用。
