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Doctoral thesis2021Open access

Shaped by the past: Resilience and ecological memory in microbial communities

Renes, Sophia


Microorganisms play a fundamental role in global biogeochemical cycles, which are increasingly being altered by the current rapid changes in the environment, threatening biodiversity and the provisioning of key ecosystem services. This thesis addresses key uncertainties surrounding the assessment of ecological resilience and the role of previous disturbances in shaping the stability especially of microbial communities to future disturbances. Firstly, a quantitative framework was developed for the assessment of ecological resilience, which combines current knowledge into a reiterative approach that gradually reduces uncertainty about the level of resilience in a system. Following this, I conducted laboratory experiments in which bacterioplankton communities were exposed to repeated disturbances, to investigate the role of disturbance history in shaping functional and structural stability under subsequent disturbances. I found that disturbance history can affect functional stability in response to both new and familiar disturbances, providing evidence of an “ecological memory” effect which then declined over time. In contrast, microbial community composition appeared to be dominated by a stochastic process, i.e. drift. This suggests the more deterministic responses of the microbial functions arose from sub-lethal effects of the disturbance on microbial activities rather than changes in community composition. These results highlight potential uncertainties associated with application of resilience frameworks developed for multicellular communities to microbial organisms, especially where non-deterministic drift dominates microbial community assembly, and variation in community structure is not strongly connected with variation in functioning.


Ecological resilience; stability; bacterioplankton; community assembly; ecological memory; disturbance history; drift

Published in

Acta Universitatis Agriculturae Sueciae
2021, number: 2021:13
ISBN: 978-91-7760-704-5, eISBN: 978-91-7760-705-2
Publisher: Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences