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Effects of disturbance intensity and frequency on bacterial community composition and function.

Berga M, Székely AJ, Langenheder S - PLoS ONE (2012)

Bottom Line: Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions.In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Genetics/Limnology, Uppsala University, Uppsala, Sweden. merce.berga@ebc.uu.se

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.

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Functional changes in the disturbance frequency experiment (Experiment 2).Values presented correspond to mean values ± standard deviation of bacterial abundance (A, B), bacterial production (C, D), total carbon substrate utilization rate (tCSUR; E, F) and number of substrates with a positive response (G, H) for the different treatments. Mean values of controls are represented as dashed lines (- -), while standard deviation from control are represented as dotted lines (···). Tukey's homogenous groups are represented by a, b and c.
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pone-0036959-g004: Functional changes in the disturbance frequency experiment (Experiment 2).Values presented correspond to mean values ± standard deviation of bacterial abundance (A, B), bacterial production (C, D), total carbon substrate utilization rate (tCSUR; E, F) and number of substrates with a positive response (G, H) for the different treatments. Mean values of controls are represented as dashed lines (- -), while standard deviation from control are represented as dotted lines (···). Tukey's homogenous groups are represented by a, b and c.

Mentions: In the case of disturbance frequency (Experiment 2), bacterial abundance was gradually reduced by increasing the number of disturbance events and was significantly lower at the highest frequencies (3x and 4x; F: 17.251, p<0.001), whereas a single perturbation event did not cause significant changes (Fig. 4A). The differences between the high frequency treatments and the low frequency and the control treatment became larger at the end of the experiment (F: 79.890, p<0.001; Fig. 4B). Bacterial abundance declined, on average and compared to the control, 24±14% after the disturbance and further decreased to 31±13 % at the end of the experiment (Fig. 4A and 4B). A similar pattern was observed for bacterial production, although significant changes occurred only at the highest frequency of disturbance (4x; F: 7.214, p<0.01; Fig. 4C). Production rates were much lower compared to the control at the end of the experiment (F: 36.585, p<0.001) than they were after the disturbance and they differed significantly from the control for all the frequencies (Fig. 4D). Bacterial production declined on average 48±26% from the control after the disturbance but was reduced to 66±13% at the end of the experiment (Fig. 4C and 4D)


Effects of disturbance intensity and frequency on bacterial community composition and function.

Berga M, Székely AJ, Langenheder S - PLoS ONE (2012)

Functional changes in the disturbance frequency experiment (Experiment 2).Values presented correspond to mean values ± standard deviation of bacterial abundance (A, B), bacterial production (C, D), total carbon substrate utilization rate (tCSUR; E, F) and number of substrates with a positive response (G, H) for the different treatments. Mean values of controls are represented as dashed lines (- -), while standard deviation from control are represented as dotted lines (···). Tukey's homogenous groups are represented by a, b and c.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3351442&req=5

pone-0036959-g004: Functional changes in the disturbance frequency experiment (Experiment 2).Values presented correspond to mean values ± standard deviation of bacterial abundance (A, B), bacterial production (C, D), total carbon substrate utilization rate (tCSUR; E, F) and number of substrates with a positive response (G, H) for the different treatments. Mean values of controls are represented as dashed lines (- -), while standard deviation from control are represented as dotted lines (···). Tukey's homogenous groups are represented by a, b and c.
Mentions: In the case of disturbance frequency (Experiment 2), bacterial abundance was gradually reduced by increasing the number of disturbance events and was significantly lower at the highest frequencies (3x and 4x; F: 17.251, p<0.001), whereas a single perturbation event did not cause significant changes (Fig. 4A). The differences between the high frequency treatments and the low frequency and the control treatment became larger at the end of the experiment (F: 79.890, p<0.001; Fig. 4B). Bacterial abundance declined, on average and compared to the control, 24±14% after the disturbance and further decreased to 31±13 % at the end of the experiment (Fig. 4A and 4B). A similar pattern was observed for bacterial production, although significant changes occurred only at the highest frequency of disturbance (4x; F: 7.214, p<0.01; Fig. 4C). Production rates were much lower compared to the control at the end of the experiment (F: 36.585, p<0.001) than they were after the disturbance and they differed significantly from the control for all the frequencies (Fig. 4D). Bacterial production declined on average 48±26% from the control after the disturbance but was reduced to 66±13% at the end of the experiment (Fig. 4C and 4D)

Bottom Line: Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions.In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Genetics/Limnology, Uppsala University, Uppsala, Sweden. merce.berga@ebc.uu.se

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.

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