Storm events impact freshwater microbial communities by transporting terrestrial viruses and other microbes to freshwater systems, and by potentially resuspending microbes from bottom sediments. The magnitude of these impacts on freshwater ecosystems is unknown and largely unexplored. Field studies carried out at two discrete sites in coastal Virginia (USA) were used to characterize the viral load carried by runoff and to test the hypothesis that terrestrial viruses introduced through stormwater runoff change the composition of freshwater microbial communities. Field data gathered from an agricultural watershed indicated that primary runoff can contain viral densities approximating those of receiving waters. Furthermore, viruses attached to suspended colloids made up a large fraction of the total load, particularly in early stages of the storm. At a second field site (stormwater retention pond), RAPD-PCR profiling showed that the viral community of the pond changed dramatically over the course of two intense storms while relatively little change was observed over similar time scales in the absence of disturbance. Comparisons of planktonic and particle-associated viral communities revealed two completely distinct communities, suggesting that particle-associated viruses represent a potentially large and overlooked portion of aquatic viral abundance and diversity. Our findings show that stormwater runoff can quickly change the composition of freshwater microbial communities. Based on these findings, increased storms in the coastal mid-Atlantic region predicted by most climate change models will likely have important impacts on the structure and function of local freshwater microbial communities.
Little is known about the composition and diversity of temperate freshwater viral communities. This study presents a metagenomic analysis of viral community composition, taxonomic and functional diversity of temperate, eutrophic Lake Matoaka in southeastern Virginia (USA). Three sampling sites were chosen to represent differences in anthropogenic impacts: the Crim Dell Creek mouth (impacted), the Pogonia Creek mouth (less impacted) and the main body of the lake (mixed). Sequences belonging to tailed bacteriophages were the most abundant at all 3 sites, with Podoviridae predominating. The main lake body harbored the highest virus genotype richness and included cyanophage and eukaryotic algal virus sequences not found at the other 2 sites, while the impacted Crim Dell Creek mouth showed the lowest richness. Cross-contig comparisons indicated that similar virus genotypes were found at all 3 sites, but at different rankabundances. Hierarchical cluster analysis of multiple viral metagenomes indicated high genetic similarity between viral communities of related environments, with freshwater, marine, hypersaline, and eukaryote-associated environments forming into clear groups despite large geographic distances between sampling locations within each environment type. These results support the conclusion that freshwater viral communities are genetically distinct from virus assemblages in other environments.KEY WORDS: Virus · Freshwater · Lake · Temperate · Metagenome · Sequencing · Virome Resale or republication not permitted without written consent of the publisher
Stormwater retention ponds are ubiquitous in urban and suburban landscapes of the United States. Most studies of the microbiology of these ponds have focused on the abundance and removal efficiency of fecal indicator bacteria. Here we provide the first comprehensive study of microbial community diversity and activity in these ponds, and assess how different environmental and engineering factors influence these communities. Watershed land-use had no grouping effect on pond geochemistry or biology. Instead, we found that microbial community composition and activity were best explained by site-specific environmental variables. 16S rRNA gene sequence analysis indicated that bacterial community structure varied greatly across sampled ponds, and appeared to be the result of autochthonous bacterial growth and not simply surface runoff. Metagenomic sequencing of pond viral communities suggested that viral taxa were influenced by external inputs, with viromes composed of bacteriophage that infect environmental bacteria, as well as viruses that infect eukaryotes and phages that infect bacteria pathogenic to eukaryotes. Collectively, our results indicate that the environmental conditions and microbial communities of these ponds vary greatly, even among ponds in close spatial proximity, and that pond microbial communities appear to be shaped by site-specific environmental factors.
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