Effects of Disturbance Intensity and Frequency on Bacterial Community Composition and Function

Abstract

Disturbances influence community structure and ecosystem functioning. Bacteria are key players in ecosystems and it is therefore crucial to understand the effect of disturbances on bacterial communities and how they respond to them, both compositionally and functionally. The main aim of this study was to test the effect of differences in disturbance strength on bacterial communities. For this, we implemented two independent short-term experiments with dialysis bags containing natural bacterial communities, which were transplanted between ambient and ‘disturbed’ incubation tanks, manipulating either the intensity or the frequency of a salinity disturbance. We followed changes in community composition by terminal restriction fragment analysis (T-RFLP) and measured various community functions (bacterial production, carbon substrate utilization profiles and rates) directly after and after a short period of recovery under ambient conditions. Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions. In the disturbance intensity experiment, the sensitivity to the disturbance and the ability of recovery differed between different functions. In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed. Moreover, in case of the intensity experiment, there was also a time lag in the responses of community composition and functions, with functional responses being faster than compositional ones. To summarize, our study shows that disturbance strength has the potential to change the functional performance and composition of bacterial communities. It further highlights that the overall effects, rates of recovery and the degree of congruence in the response patterns of community composition and functioning along disturbance gradients depend on the type of function and the character of the disturbance.

Linking microbial community structure to β-glucosidic function in soil aggregates

“…Biochemical functionality has been shown to return to a pre disturbance state before community structure does likewise (Berga et al, 2012), and in many studies, community structure never returns to the original state. This begs questions as to the scale at which functional redundancy is active.…”

Microbial composition affects the functioning of estuarine sediments

“…Generally, ecosystem models assume that process rates-even when directly carried out by microorganisms-are determined by environmental conditions (Schimel and Gulledge, 1998), implicitly assuming that microbial communities are so physiological plastic that any differences in their composition are unimportant. Future transplant experiments might also consider more detailed temporal dynamics of microbial composition and functioning over time (for example, Berga et al, 2012). Such a design could test whether microbial composition influences the resilience of ecosystem processes to environmental change under field conditions.…”

The legacy of the past: effects of historical processes on microbial metacommunities

“…This is, to our knowledge, still the only study that has clearly shown that abiotic historical contingencies constrain changes in bacterial community composition at the metacommunity scale, even though it is not known for how long back in time these constraints exist. Time-lags of several days between environmental conditions and community responses have been observed in bacterio-and phytoplankton communities (Berga et al 2012, Recknagel et al 2013, suggesting that changes in community composition lag behind changes in the environment. Based on this, one could presume that legacy effects should be transient; but this needs to be investigated further.…”