GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Spain.
Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain.
Sci Total Environ. 2020 Apr 20;714:136838. doi: 10.1016/j.scitotenv.2020.136838. Epub 2020 Jan 22.
Microbiota inhabiting the intermittent streambeds mediates several in-stream processes that are essential for ecosystem function. Reduced stream discharge caused by the strengthened intermittency and increased duration of the dry phase is a spreading global response to changes in climate. Here, the impacts of a 5-month desiccation, one-week rewetting and punctual storms, which interrupted the dry period, were examined. The genomic composition of total (DNA) and active (RNA) diversity, and the community level physiological profiles (CLPP) were considered as proxies for functional diversity to describe both prokaryotes and eukaryotes inhabiting the surface and hyporheic streambeds. Comparisons between the genomic and potential functional responses helped to understand how and whether the microbial diversity was sensitive to the environmental conditions and resource acquisition, such as water stress and extracellular enzyme activities, respectively. RNA expression showed the strongest relationship with the environmental conditions and resource acquisition, being more responsive to changing conditions compared to DNA diversity, especially in the case of prokaryotes. The DNA results presumably reflected the legacy of the treatments because inactive, dormant, or dead cells were included, suggesting a slow microbial biomass turnover or responses of the microbial communities to changes mainly through physiological acclimation. On the other hand, microbial functional diversity was largely explained by resources acquisition, such as metrics of extracellular enzymes, and appeared vulnerable to the hydrological changes and duration of desiccation. The data highlight the need to improve the functional assessment of stream ecosystems with the application of complementary metrics to better describe the streambed microbial dynamics under dry-rewet stress.
栖息在间歇性溪流床中的微生物群介导了几个对生态系统功能至关重要的溪流内过程。由于间歇性增强和干燥阶段持续时间增加导致的溪流流量减少，是气候变化下全球范围的普遍反应。在这里，研究了为期 5 个月的干燥、一周的再湿润和间歇性的暴雨（中断了干燥期）的影响。总（DNA）和活性（RNA）多样性的基因组组成以及群落水平生理特征（CLPP）被视为功能多样性的代表，用于描述栖息在溪流表面和潜流带中的原核生物和真核生物。比较基因组和潜在功能反应有助于了解微生物多样性如何以及是否对环境条件和资源获取（例如水分胁迫和胞外酶活性）敏感。RNA 表达与环境条件和资源获取之间表现出最强的关系，与 DNA 多样性相比，它对变化的条件更为敏感，尤其是在原核生物的情况下。DNA 结果可能反映了处理的遗留问题，因为其中包括非活动、休眠或死亡的细胞，这表明微生物生物量的周转率较慢，或者微生物群落主要通过生理适应来对变化做出反应。另一方面，微生物功能多样性主要由资源获取来解释，如胞外酶的度量，并且似乎容易受到水文变化和干燥持续时间的影响。这些数据强调需要改进溪流生态系统的功能评估，应用补充指标来更好地描述在干湿胁迫下的溪流床微生物动态。
