Journal Article

Spatiotemporal analysis of microbial community dynamics during seasonal stratification events in a freshwater lake (Grand Lake, OK, USA)

Morrison, Jessica M., Baker, Kristina D., Youssef, Noha H., Zamor, Richard M., Elshahed, Mostafa S., Nikolai, Steve

2017

Overview

Many freshwater lakes undergo seasonal stratification, where the formation of phototrophic blooms in the epilimnion and subsequent sedimentation induces hypoxia/anoxia in the thermocline and hypolimnion. This autochthonously produced biomass represents a major seasonal organic input that impacts the entire ecosystem. While the limnological aspects of this process are fairly well documented, relatively little is known regarding the microbial community response to such events, especially in the deeper anoxic layers of the water column. Here, we conducted a spatiotemporal survey of the particle-associated and free-living microbial communities in a warm monomictic freshwater reservoir (Grand Lake O' the Cherokees) in northeastern Oklahoma, USA. Pre-stratification samples (March) harbored a homogeneous community throughout the oxygenated water column dominated by typical oligotrophic aquatic lineages (acl clade within Actinobacteria, and Flavobacterium within the Bacteroidetes). The onset of phototrophic blooming in June induced the progression of this baseline community into two distinct trajectories. Within the oxic epilimnion, samples were characterized by the propagation of phototrophic (Prochlorococcus), and heterotrophic (Planctomycetes, Verrucomicrobia, and Beta-Proteobacteria) lineages. Within the oxygen-deficient thermocline and hypolimnion, the sedimentation of surface biomass induced the development of a highly diverse community, with the enrichment of Chloroflexi, \"Latescibacteria\", Armatimonadetes, and Delta-Proteobacteria in the particle-associated fraction, and Gemmatimonadetes and \"Omnitrophica\" in the free-living fraction. Our work documents the development of multiple spatially and temporally distinct niches during lake stratification, and supports the enrichment of multiple yet-uncultured and poorly characterized lineages in the lake's deeper oxygen-deficient layers, an ecologically relevant microbial niche that is often overlooked in lakes diversity surveys.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Abiotic factors / Aggregates / Agricultural management / Agricultural wastes / Agronomy / Algae / Algal blooms / Anoxia / Aquatic ecosystems / Atmospheric temperature / Atomic force microscopy / Bacteria / Biology and Life Sciences / Biomass / Buoyancy / Carbon / Carbon fixation / Cell culture / Climate change / Community structure / Contamination / Continents / Deposition / Earth Sciences / Ecology and Environmental Sciences / Ecosystem / Epilimnion / Fresh Water - microbiology / Freshwater ecology / Freshwater lakes / Geochemistry / Geography / Heterotrophs / Hypolimnion / Hypoxia / Inventories / Lake stratification / Lakes / Life cycles / Metabolism / Microbial activity / Microbial colonies / Microbiomes / Microorganisms / Niches / Nitrogen / Oxidation / Oxygen / Parasitism / pH effects / Photosynthesis / Physical Sciences / Phytoplankton / Propagation / Pure culture / Research and Analysis Methods / River ecology / Runoff / Seasons / Sedimentation / Sedimentation & deposition / Spatio-Temporal Analysis / Stockpiling / Stratification / Stratification (Geology) / Temperature effects / Thermocline / Water chemistry / Water circulation / Water column / Water Microbiology / Water quality