Tuesday, August 5, 2008 - 9:00 AMOOS 5-4: Disturbance in aquatic microbial communities
Ashley Shade, University of Wisconsin - Madison and Katherine D. McMahon, University of Wisconsin - Madison.
Background/Question/Methods
Disturbance is the periodic disruption of ecosystem, community, or population structure, or changes in resource availability or the physical environment. Multiple related ecological concepts emerge directly disturbance theory. For example, studies of community succession, habitat heterogeneity, and metacommunity dynamics often rely on a disturbance framework. Despite this interweave of disturbance with other theoretical branches of ecology, researchers are yet challenged by the influence of observational scale. After fire disturbance, it may take decades to observe forest succession to a climax community. In contrast, microbial communities have rapid generation times and response to environmental stimuli; this allows for relevant observation timescales of hours to months. Thus, microbes may serve as advantageous models for testing traditional disturbance theory.
Results/Conclusions
Lake overturn acts as a disturbance because it alters physical and chemical gradients in the previously stratified water column. In a stratified lake, the upper layer (epilimnion), is relatively warmer, limited in nutrients, and high in dissolved oxygen, while the lower layer (hypolimnion) is cooler, rich in nutrients, and anaerobic to anoxic. Within the context of lake stratification and mixis, we synthesize four related aspects of mixing disturbance on aquatic microbial communities. First we explore the potential influence of seasonal mixis on the observed inter-annual “re-setting” and succession of aquatic bacterial communities. Next we investigate variation of bacterial communities across lakes that experience different mixing frequencies and habitat heterogeneity gradients. Third we compare the influence of episodic versus seasonal disturbance in a unique lake that experiences both typhoon-initiated and seasonal winter mixis. Finally we experimentally examine the specific response of lake microbial metacommunities to temperature and dissolved oxygen gradients that may act as habitat filters. We find overall evidence that microbial communities “follow similar rules” as macro-scale organisms with respect to disturbance, and suggest that microbes can lead us to more generalized disturbance theories.
Disturbance is the periodic disruption of ecosystem, community, or population structure, or changes in resource availability or the physical environment. Multiple related ecological concepts emerge directly disturbance theory. For example, studies of community succession, habitat heterogeneity, and metacommunity dynamics often rely on a disturbance framework. Despite this interweave of disturbance with other theoretical branches of ecology, researchers are yet challenged by the influence of observational scale. After fire disturbance, it may take decades to observe forest succession to a climax community. In contrast, microbial communities have rapid generation times and response to environmental stimuli; this allows for relevant observation timescales of hours to months. Thus, microbes may serve as advantageous models for testing traditional disturbance theory.
Results/Conclusions
Lake overturn acts as a disturbance because it alters physical and chemical gradients in the previously stratified water column. In a stratified lake, the upper layer (epilimnion), is relatively warmer, limited in nutrients, and high in dissolved oxygen, while the lower layer (hypolimnion) is cooler, rich in nutrients, and anaerobic to anoxic. Within the context of lake stratification and mixis, we synthesize four related aspects of mixing disturbance on aquatic microbial communities. First we explore the potential influence of seasonal mixis on the observed inter-annual “re-setting” and succession of aquatic bacterial communities. Next we investigate variation of bacterial communities across lakes that experience different mixing frequencies and habitat heterogeneity gradients. Third we compare the influence of episodic versus seasonal disturbance in a unique lake that experiences both typhoon-initiated and seasonal winter mixis. Finally we experimentally examine the specific response of lake microbial metacommunities to temperature and dissolved oxygen gradients that may act as habitat filters. We find overall evidence that microbial communities “follow similar rules” as macro-scale organisms with respect to disturbance, and suggest that microbes can lead us to more generalized disturbance theories.