Zhang Yun, Li Kaidi, Zhou Qichao, Chen Le, Yang Xuan, Zhang Hucai
Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Sciences, Yunnan University, Kunming, 650500, China.
Yunnan Key Laboratory of Pollution Process and Management of Plateau Lake-Watershed, Yunnan Research Academy of Eco-environmental Sciences, Kunming, 650034, China.
Environ Sci Pollut Res Int. 2021 Jun;28(23):29931-29944. doi: 10.1007/s11356-021-12705-3. Epub 2021 Feb 12.
Multiple stressors associated with global change are influencing the phytoplankton taxonomic composition and biomass in plateau lakes, such as higher levels of ultraviolet radiation (UVR, 280-400 nm) and the risk of eutrophication. Although the restrictive effects of high UVR on phytoplankton are generally recognized, the effects will be impacted by the UVR levels of seasonal changes and the nutrient status. In this study, in situ phytoplankton productivity was measured seasonally under full solar radiation and only visible light (photosynthetically active radiation, PAR) conditions in the plateau oligotrophic Lake Fuxian, Southwest China. To determine the single effects of UVR and nutrient enrichment and their combined impact on phytoplankton communities, a mesocosm experiment (1 month) was conducted outdoors during late summer (rainy season). The interactive experiment was designed with two radiation treatments (UVR + PAR and PAR) and four nutrient treatments (raw water, nitrogen addition, phosphorus addition, nitrogen and phosphorus addition). Our results suggested that the response of phytoplankton to UVR depended largely on nutrient availability, which was embodied in the no significant responses of phytoplankton productivity and total biomass to UVR in the oligotrophic raw water from Lake Fuxian, but the positive responses of total biomass to UVR in the nutrient enrichment treatment. Furthermore, the response of phytoplankton to UVR was also taxa dependent. Chlorophytes and dinoflagellates showed positive response to UVR, whereas chrysophytes were quite sensitive to UVR; diatoms had no significant response to UVR under all nutrient conditions, while the response of cyanobacteria to UVR was highly dependent on nutrient status. This study highlights that the increase in nutrient concentrations in oligotrophic lake not only directly promotes the growth of phytoplankton but also combines with low UVR during summer to benefit the growth of eutrophic taxa based on the non-negative effect of UVR on total phytoplankton biomass and the positive effect on eutrophic taxa.
与全球变化相关的多种压力源正在影响高原湖泊中浮游植物的分类组成和生物量，例如更高水平的紫外线辐射（UVR，280 - 400纳米）以及富营养化风险。尽管高紫外线辐射对浮游植物的限制作用已得到普遍认可，但这些影响会受到季节变化的紫外线辐射水平和营养状况的影响。在本研究中，在中国西南部高原贫营养的抚仙湖，季节性地测量了在全太阳辐射和仅可见光（光合有效辐射，PAR）条件下的原位浮游植物生产力。为了确定紫外线辐射和营养物质富集的单一影响及其对浮游植物群落的综合影响，在夏末（雨季）进行了为期1个月的室外中宇宙实验。交互实验设计了两种辐射处理（UVR + PAR和PAR）和四种营养处理（原水、添加氮、添加磷、添加氮和磷）。我们的结果表明，浮游植物对紫外线辐射的响应在很大程度上取决于营养物质的可利用性，这体现在抚仙湖贫营养原水中浮游植物生产力和总生物量对紫外线辐射无显著响应，但在营养物质富集处理中总生物量对紫外线辐射呈正响应。此外，浮游植物对紫外线辐射的响应也取决于分类群。绿藻和甲藻对紫外线辐射呈正响应，而金藻对紫外线辐射相当敏感；硅藻在所有营养条件下对紫外线辐射均无显著响应，而蓝细菌对紫外线辐射的响应高度依赖于营养状况。本研究强调，贫营养湖泊中营养物质浓度的增加不仅直接促进浮游植物的生长，而且在夏季与低水平的紫外线辐射相结合，基于紫外线辐射对浮游植物总生物量的非负影响以及对富营养分类群的积极影响，有利于富营养分类群的生长。
