U.S. Environmental Protection Agency Office of Research and Development, Cincinnati, OH, USA.
Institute of Hydrobiology, Jinan University, Guangzhou, Guangdong, China.
Sci Rep. 2019 Feb 21;9(1):2480. doi: 10.1038/s41598-019-38481-2.
The efforts towards reduction of nutrient contamination of surface waters have greatly gained attention to mitigate increasing incidences of harmful cyanobacterial blooms (CyanoHABs), but little attention has been paid on the roles and importance of cyanobacterial N-fixation and phosphorus (P) scavenging pathways during cyanoHABs. Meta-transcriptomic analyses revealed that expressions of genes involved in N-fixation (nifDKH) and P-scavenging were significantly upregulated during the bloom compared to pre-bloom in Harsha Lake. The activities of N-fixation occurred during early summer after a late spring phytoplankton bloom, and were associated with high phosphorus and low nitrogen. The highly active cyanobacterial N-fixers were dominated by Nostoc and Anabaena. Following the activities of N-fixation and production of new nitrogen, an early summer Microcystis-dominated bloom, a shift of dominance from Nostoc and Anabaena to Microcystis and an increase of microcystin and saxitoxin occurred. By contrast, P-scavenging activities dominated also by Nostoc and Anabaena were associated with low P and the Microcystis bloom. This information can be used to aid in the understanding the impact that nitrogen and phosphorus have on the early summer CyanoHAB and the functional activities of Nostoc- and Anabaena-dominated or Microcystis-dominated communities, and aid in making management decisions related to harmful algal blooms.
减少地表水中营养物质污染的努力极大地引起了人们的关注，以减轻有害蓝藻水华（CyanoHABs）的日益增加，但在 CyanoHABs 期间，蓝藻固氮和磷（P）摄取途径的作用和重要性几乎没有得到关注。元转录组分析显示，与 Harsha 湖的开花前相比，在开花期间，与固氮（nifDKH）和 P 摄取相关的基因表达显著上调。固氮作用发生在春末浮游植物大量繁殖之后的初夏，与高磷和低氮有关。高活性蓝藻固氮菌主要由 Nostoc 和 Anabaena 组成。在固氮作用和新氮的产生之后，初夏的微囊藻水华占主导地位，从 Nostoc 和 Anabaena 到 Microcystis 和微囊藻毒素和石房蛤毒素的增加的优势发生了转变。相比之下，也由 Nostoc 和 Anabaena 主导的 P 摄取活动与低磷和微囊藻水华有关。这些信息可用于帮助了解氮和磷对初夏 CyanoHAB 的影响以及 Nostoc 和 Anabaena 或 Microcystis 占主导地位的群落的功能活动，并有助于做出与有害藻类水华有关的管理决策。
