Tulane University New Orleans, Louisiana, United States
Background/Question/Methods
Stability is defined as a community’s ability to return to equilibrium following a disturbance, measured by resistance (sensitivity to a disturbance) and resilience (rate of recovery). Microbes represent a novel system to study stability as short generation times and dormancy may produce response patterns distinct from macro communities. Current lab and field-based research of microbial stability find conflicting results, as microbes respond to environmental change over weeks-months in the field, but hours-days in the lab. This suggests we have yet to determine an appropriate timescale upon which to measure microbial change in nature. Ecological factors, such as historic disturbance regimes, or legacy effects, can also influence stability by increasing resistance and resilience and altering response patterns. To investigate microbial stability under varying ecological conditions we sequenced soil bacteria from 24 1m2 plots in a coastal marsh following a salinity addition. Legacy plots received monthly salinity additions for two years prior to the experimental disturbance and are compared to Control and Pulse plots, which received only one salinity addition. We hypothesize that 1) a disturbance legacy increases community resistance to disturbance, and 2) legacy communities will return to the pre-disturbance state more quickly than communities without a legacy, representing higher resilience.
Results/Conclusions
Results from ordination indicate that the greatest change in community composition in both treatments came three days following the disturbance. This suggest that microbial communities can respond to environmental change in nature within days and represents one of the most rapid microbial community changes captured in the field. Results also suggest that communities with a legacy effect have increased resistance to disturbance compared to communities without a legacy, seen as less drastic compositional shifts relative to the pre-disturbance community. Both treatment communities returned to initial composition approximately 8-14 days following the disturbance, indicating high resilience regardless of legacy. Overall, these results indicate that microbial communities respond to and recover from environmental change rapidly. A history of disturbance increases resistance, suggesting that novel disturbances to an ecosystem could increase the magnitude of compositional, and potentially functional, change.
