Thesis defence by Arunima Sikder

Title: "The influence of acclimation and diversity on impact and recovery in a globally relevant phytoplankton system exposed to global change"

Abstract:

Environmental change rarely arrives as a single, isolated event; organisms and communities typically experience one stressor against the backdrop of another already passed. Arunima Sikder's doctoral thesis asks whether an organism's past environment shapes its response to the environment that follows, and whether that influence propagates upward to affect the stability of the communities these organisms belong to.
The thesis addresses this question in Synechococcus sp., a globally significant marine primary producer, using thermal and chemical stressors as its two environmental drivers. Working across three levels of biological organisation, the work accounts for how past environments shape responses to subsequent ones arriving in sequence, in fluctuation, or in combination — with functional traits as the common currency for measuring these responses.
The results show three things. First, sensitivity to a stressor depends on the sequence of exposure, not on the stressor alone. Second, response diversity predicts community stability only when measured under the community's actual acclimation history, rather than under sustained conditions as convention assumes. Third, an apparent contradiction of biodiversity–ecosystem-function theory — a negative relationship between functional diversity and performance.
Together, these findings argue that sensitivity, response diversity, and functional diversity should be treated as state-dependent quantities rather than fixed properties, with consequences for how the performance of biological systems is measured and modelled under increasingly variable environmental regimes.

Arunima will present the results of her PhD thesis, conducted in the Biology Department (URBE) under the supervision of Frederik De Laender. 

A link to TEAMS will be provided at a later stage to follow the defence online.