Succession of Microbial Community in a Small Water Body within the Alluvial Aquifer of a Large River

Abstract

Nitrogen is one of the essential elements limiting growth in aquatic environments. Being primarily of anthropogenic origin, it exerts negative impacts on freshwater ecosystems. The present study was carried out at the nitrate-vulnerable zone within the alluvial aquifer of the large lowland Drava River. The main aim was to investigate the ecosystem’s functionality by characterizing the bacterial and phytoplankton diversity of a small inactive gravel pit by using interdisciplinary approaches. The phytoplankton community was investigated via traditional microscopy analyses and environmental DNA (eDNA) metabarcoding, while the bacterial community was investigated by a molecular approach (eDNA). Variations in the algal and bacterial community structure indicated a strong correlation with nitrogen compounds. Summer samples were characterized by a high abundance of bloom-forming Cyanobacteria. Following the cyanobacterial breakdown in the colder winter period, Bacillariophyceae and Actinobacteriota became dominant groups. Changes in microbial composition indicated a strong correlation between N forms and algal and bacterial communities. According to the nitrogen dynamics in the alluvial aquifer, we emphasize the importance of small water bodies as potential buffer zones to anthropogenic nitrogen pressures and sentinels of the disturbances displayed as algal blooms within larger freshwater systems.

Characteristics and particularities of bacterial community variation in the offshore shellfish farming waters of the North Yellow Sea

“…The proportional abundance of Actinobacteriota (1.3%) in this study was obviously lower than that in other studies, in which it was reported up to 5%-20% (He et al, 2017;Yu et al, 2018). The abundance of Actinobacteriota has been proved to be strongly correlated with nitrogen cycling, and it can thrive under oligotrophic conditions and be suppressed with high organic matter and inorganic nutrient availability (Kulašet al, 2021;Wang et al, 2021). The impact of shellfish farming on nitrogen cycling has been investigated in previous reports by analyses of water/sediment quality parameters (Erler et al, 2017;Jiang et al, 2020;Pan et al, 2021).…”