Switch of Bacteria Community Under Oxygen Depletion in Sediment of Bohai Sea

Abstract

Regular oxygen depletion is occurring every summer in the depression area of the Bohai Sea. The community structure and potential functions of microbes in expanding marine hypoxic area are of great importance due to their roles in biogeochemical cycling. In this study, the diversity and distribution of bacteria based on 16S rRNA gene in sediment along an inshore-offshore transect across the oxygen-depletion area in the Bohai Sea was investigated in June, July and August of 2018 by employing high-throughput sequencing. Results revealed that the bacteria community was dominated by Proteobacteria (42.67%), Actinobacteria (14.13%), Chloroflexi (13.02%), Acidobacteria (8.01%), and Bacteroidetes (6.30%). During oxygen depletion, the bacteria community from inshore site A3 subjected to dramatic variation from June to August, but the composition tended to be stable in sites from the depression area along the transect. Distinct switch of bacteria from aerobic to anaerobic group was observed when the DO concentration <4.2 mg/L, typically represented by dominance of Anaerolineaceae in August sample. Further, KEGG prediction by PICRUSt confirmed the variations by showing significant difference in functional pathways, especially the nitrogen metabolisms, before and after DO depletion (p < 0.05). These variations could be influenced by depth, NO2– concentration and DO availability based on RDA analysis. The details in diversity and composition of bacteria under continually observation provide insights into both instant and long-term response of bacteria community to oxygen depletion, and the distinct functional switch under this process expands our knowledge on the metabolic character of bacteria in worldwide hypoxia areas.

Comparison of assembly process and co-occurrence pattern between planktonic and benthic microbial communities in the Bohai Sea

“…In line with some studies in the BS ( Chen et al, 2020 ; Guo et al, 2022 ; Wu et al, 2022 ), Proteobacteria , Bacteroidetes , and Cyanobacteria were found to be dominant groups and were abundant in both water and sediments. These groups have been characterized as the important groups in eutrophic coastal ecosystems ( Klawonn et al, 2016 ; Gomes et al, 2019 ; Zhang et al, 2019 ; Zhao et al, 2021 ).…”

Understanding the Variation of Bacteria in Response to Summertime Oxygen Depletion in Water Column of Bohai Sea

“…The polymerase chain reaction (PCR) was performed in a 20 μl mixture, containing 4 μl of 5× FastPfu Buffer, 2 μl of dNTPs (2.5 mM), 0.8 μl of each primer (5 μM), 0.4 μ of FastPfu polymerase, and 10 ng of template DNA. Amplification and purification of 16S rRNA product followed the protocols in Guo et al (2022) , and protocols for nosZ gene were after Wang J. et al (2019) .…”

Ideas and perspectives. The fluctuating nature of oxygen shapes the ecology of aquatic habitats and their biogeochemical cycles: the aquatic oxyscape

“…While water temperature is only linked to meteorological changes, the oxygen concentration in productive aquatic environments is also regulated by the biota component (Chapman, 2021). Community composition of primary producers (Power and Cardinale, 2009), rainfall level (Mallin et al, 1993), nutrients' runoff (Kinney and Roman, 1998), biotic networks (Graham et al, 2018;Breen and Mann, 1976), and bacterial community dynamics (Guo et al, 2022), govern, at a small scale, high spatial and temporal change in the concentrations of dissolved oxygen. The interaction of all these factors strongly affects dissolved oxygen fluctuations beyond the levels that can be predicted from just the meteorological trends.…”

“…End products of anaerobic metabolisms such as ammonium, sulphur and methane are consumed when oxygen becomes available again during the daylight and the recovery of photosynthesis, re-establishing aerobic respiration as the central metabolism of the microbial communities (Fenchel and Finlay, 2008). For example, in the Bohai Sea (China), under oxygen concentration lower than 4.2 mg/L the microbial communities were dominated by bacteria of the Anaerolineaceae (Guo et al, 2022). In Chilean coast ecosystems, the composition of the bacterial communities is regulated by the seasonality of the upwelling waters, with the partitioning of community composition driven by dissolved oxygen.…”