Title: Disentangling Drivers of Aquatic Microbial Community
Dynamics
Microbial communities regulate the flow of nutrients and energy in the
Earth's biosphere, but relatively little is known about the forces that govern
their structures and functions. Quantifying the influence of these ecological
drivers is essential to understanding microbially-mediated processes.The
North Temperate Lakes Microbial Observatory conducted time series
observations of aquatic microbial populations to examine drivers of
microbial community dynamics. Our long-term observations revealed
synchrony in community-level dynamics among phytoplankton and
bacteria in six north temperate humic lakes. The influence of regional
meteorological factors explained much of the temporal variability in the
phytoplankton community, and resulted in synchronous patterns of
community change among lakes. Bacterial dynamics, in contrast, were
driven by system-specific interactions with phytoplankton. To investigate
bacterial use of phytoplankton exudates as a mechanism contributing to
the correlated patterns of community change, we characterized the
diversity and dynamics of heterotrophic bacterioplankton with genetic
potential to use glycolate, a photorespiration-specific exudate, in these
lakes in both time-series and mesocosm experiments. Our results indicate
that biological interactions are a primary driver of aquatic bacterial
populations, and that these biological interactions transmit the signal of
regional extrinsic drivers to the bacterial communities. Sorting out the
relative influence of drivers of bacterial community dynamics can provide a
framework for understanding and predicting the effect of future
environmental change on aquatic microbial communities and their
ecosystem services.