57 / 2024-09-04 09:12:08
Effects of warming on the diversity of active and dormant microbes in mangrove wetlands
Warming, Sediment, Microbes, Physiological state, Community
Session 13 - Coastal Environmental Ecology under anthropogenic activities and natural changes
Abstract Review Pending
Microbial diversity in sediments and soils is exceptionally high, and changes in their activity and physiological states play critical roles in the biogeochemical cycling of key nutrients, as well as in ecosystem resilience and recovery. Existing studies have revealed that sediments and soils contain a substantial number of dead cells, incompletely degraded extracellular DNA, and cells that are still alive but not physiologically active (dormant cells). Consequently, sequencing based on directly extracted environmental DNA (eDNA) can overestimate microbial diversity, potentially leading to biases in functional predictions and introducing significant uncertainty into assessments of the ecological impacts of global change.
We have proposed a novel approach for parallel sequencing and integrated analysis of eDNA, eRNA, and propidium monoazide (PMA)-treated eDNA from environmental samples, termed the “Triple-Metabarcoding Analysis” (TMA), which is designed to identify the active, dormant, and dead microbes, as well as their community composition and dynamics in environmental samples (Deng et al. 2024, Environmental Microbiology). Application of the TMA method revealed that both dead and dormant eukaryotic microbes constitute a significant proportion in intertidal sediments. More recently, we investigated further the effects of warming on the diversity and dynamics of active and dormant bacteria and microeukaryotes using the TMA method and based on a laboratory-based warming simulation experiment of mangrove sediments. The main findings are as follows:
- In the total rDNA pools of bacteria and microeukaryotes, the sequences corresponding to active ASVs accounted for only 55% and 61%, respectively, with dormant comprising 19% and 10%, and dead comprising 26% and 29%.
- After two weeks of incubation at +2°C, the proportions of active bacterial and microeukaryotic sequences in their rDNA pools increased significantly. At +4°C, these proportions decreased, especially for bacteria. A similar decrease in active bacterial sequences was noted at ambient temperature, indicating the reductions were likely due to factors other than warming, such as biotic interactions. The proportions of dormant bacterial and microeukaryotic sequences also decreased, but not significantly compared to the control.
- After four weeks of incubation under warming conditions (+2°C and +4°C), the ASV diversity of active bacteria increased significantly compared to the control, whereas the diversity of dormant bacteria remained unchanged. A 2°C increase in temperature did not significantly impact the diversity of active or dormant microeukaryotes. However, incubation at +4°C for four weeks led to a significant decrease in the diversity of dead microeukaryotes.