| Authors: | Mark J. Rozmarynowycz, Benjamin F.N. Beall, George S. Bullerjahn, Gaston E. Small, Robert W. Sterner, Sandra S. Brobold, Nigel A. D'souza, Susan B. Watson, Robert Michael L. McKay |
| Title: | Transitions in microbial communities along a 1600 km freshwater trophic gradient |
| Published in: | Journal of Great Lakes Research (2019) |
| Key words: | amplicon sequencing, Bacteria, flow cytometry, Laurentian Great Lakes, trophic state |
| Abstract: | This study examined vertically-resolved patterns in microbial community structure across a freshwater trophic gradient extending 1600 km from the oligotrophic waters of Lake Superior to the eutrophic waters of Lake Erie, the most anthropogenically influenced of the Laurentian Great Lakes system. Planktonic bacterial communities clustered by Principal Coordinates Analysis (PCoA) on UniFrac distance matrices into four groups representing the epilimnion and hypolimnion of the upper Great Lakes (Lakes Superior and Huron), Lake Superior's northern bays (Nipigon and Black bays), and Lake Erie. The microbes within the upper Great Lakes hypolimnion were the most divergent of these groups with elevated abundance of Planctomycetes and Chloroflexi compared to the surface mixed layer. Statistical tests of the correlation between distance matrices identified temperature and sample depth as the most influential community structuring parameters, reflecting the strong UniFrac clustering separating mixed-layer and hypolimnetic samples. Analyzing mixed-layer samples alone showed clustering patterns were correlated with nutrient concentrations. Operational taxonomic units (OTU) which were differentially distributed among these conditions often accounted for a large portion of the reads returned. While limited in coverage of temporal variability, this study contributes a detailed description of community variability that can be related to other large freshwater systems characterized by changing trophic state. |
| Datasets [for which this is the primary paper]: | Transect across the Laurentian Great Lakes in 2011 and 2012 |