Stress Echoes: Past Environments Shape Population Responses to Fluctuating Stress in Synechococcus sp.

In an ever-changing climate, global change factors are rarely consistent and often fluctuate, creating sequential stresses on ecosystems. Under such conditions, does a population's environmental history affect its response to future changes? <br/><br/>This study examines the influence of stress acclimation on the population responses of Synechococcus sp., a globally dominant marine cyanobacteria. We selected six strains from different habitats (warm and cold oceans) and experimentally manipulated their environmental histories through short-term exposure to two stressors: temperature and pollution. We then tracked population growth and functional traits across three different stress sequences. Our findings reveal that environmental history significantly shapes future responses: cross-tolerance can develop when environments differ, while repeated exposure to the same stressor may lead to stress build-up. Using generalized additive models, we found that functional traits and density feedback consistently predict population responses, highlighting their potential as key indicators of population dynamics in fluctuating environments