Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Nankai International Advanced Research Institute (Shenzhen Futian), Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China.
State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai International Advanced Research Institute (Shenzhen Futian), Nankai University, Tianjin, China.
Sci Total Environ. 2024 Jul 20;935:173477. doi: 10.1016/j.scitotenv.2024.173477. Epub 2024 May 23.
Human activities have caused an imbalance in the input nitrogen and phosphorus (N/P) in the biosphere. The imbalance of N/P is one of the characteristics of water eutrophication, which is the fundamental factor responsible for the blooms. The effects of the N/P imbalance on diatom and phycospheric bacteria in blooms are poorly understood. In this study, the N/P molar ratio in real water (14:1) and the predicted N/P molar ratio in future water (65:1) were simulated to analyze the response of Cyclotella sp. and phycospheric bacteria to the N/P imbalance. The results showed that the N/P imbalance inhibited the growth of Cyclotella sp., but prolonged diatom bloom duration. The resistance of Cyclotella sp. to the N/P imbalance is related to phycospheric bacteria, and there are dynamic regulatory mechanisms within the phycospheric bacteria community to resist the N/P imbalance: (1) the increase of HNA bacterial density, the decrease of LNA bacterial density, (2) the increase of phycospheric bacterial diversity and eutrophic bacteria abundance, and the change of denitrifying bacteria abundance, (3) the activity of nitrogen and phosphorus metabolism of HNA bacteria enhanced, while that of LNA bacteria decreased. And the gene hosts of nitrogen and phosphorus metabolism were most enriched in Proteobacteria, indicating that Proteobacteria played an important role in maintaining the stability of phycospheric bacteria and was the dominant phylum resistant to the N/P imbalance. This study clarified that the algal-bacteria system was resistant to the N/P imbalance and implied that the N/P imbalance had little effect on the occurrence of diatom bloom events due to the presence of phycospheric bacteria.
人类活动导致生物圈中输入的氮磷（N/P）失衡。N/P 失衡是水体富营养化的特征之一，是引发水华的根本因素。N/P 失衡对水华期硅藻和藻际细菌的影响尚不清楚。本研究模拟实际水体中 N/P 摩尔比（14:1）和未来水体中预测的 N/P 摩尔比（65:1），分析了 Cyclotella sp. 对 N/P 失衡的响应以及藻际细菌的响应。结果表明，N/P 失衡抑制了硅藻的生长，但延长了硅藻水华的持续时间。硅藻对 N/P 失衡的抵抗力与藻际细菌有关，藻际细菌群落内部存在动态调节机制来抵抗 N/P 失衡：（1）HNA 细菌密度增加，LNA 细菌密度降低，（2）藻际细菌多样性和富营养细菌丰度增加，反硝化细菌丰度发生变化，（3）HNA 细菌的氮磷代谢活性增强，而 LNA 细菌的氮磷代谢活性降低。氮磷代谢的基因宿主在变形菌门中最丰富，表明变形菌门在维持藻际细菌稳定性方面发挥着重要作用，是抵抗 N/P 失衡的主要门。本研究阐明了藻类-细菌系统对 N/P 失衡具有抵抗力，并暗示由于藻际细菌的存在，N/P 失衡对硅藻水华事件的发生影响不大。
