Functional Diversity of Bacterioplankton in Three North Florida Freshwater Lakes over an Annual Cycle

The phylogenetic diversity of freshwater bacterioplankton is widely known; however, there is minimal information on the functional diversity of the bacterial communities in these systems. Understanding the functional diversity of freshwater bacterial communities is important because heterotrophic bacteria can be impacted by anthropogenic perturbation, which in turn can alter biogeochemical cycling. The objective of this study was to use Biolog EcoPlates to acquire spatial and temporal community-level physiological profiles (CLPPs) for three freshwater lakes of different trophic levels and to assess the phylogenetic affiliation of the bacteria responsible for utilizing the various carbon guilds within them by denaturing gradient gel electrophoresis (DGGE). CLPP results showed that bacterial communities utilized the carbon guilds similarly between sites within the three lakes. However, when the metabolic profile of each lake was compared, Lake Bradford and Moore Lake were more similar to one another than to Lake Munson, the eutrophic lake. Additionally, although the bacteria that utilized the five carbon guilds included representatives from the classes α-, β-, γ-Proteobacteria, Flavobacteria and Sphingobacteria, Lake Munson had the largest number of Flavobacteria and γ-Proteobacteria in comparison to Moore Lake and Lake Bradford. Overall, Biolog analysis was useful in identifying differences in the functional diversity of bacterial communities between lakes of different trophic statuses and can be used as a tool to assess ecosystem health.