Communities of photosynthesising and nutrient-cycling microorganisms are fundamental to life and rely on chemical crosstalk to mediate the interactions within their community to function efficiently. In aquatic ecosystems, communities of microalgae and bacteria share micro-habitats in which the interplay of photosynthesis and respiration can cause steep gradients of pH and oxygen. Research over the past years revealed that communication chemicals of different kinds of organisms can be permanently or temporarily inactivated through chemical alteration due to pH conditions that are fluctuating on a level comparable to or even smaller than the level observed within microalgae-bacteria communities.  This presentation aims to provide first insights into the hypothesis that diel abiotic gradients can temporarily modulate the essential chemical interactions that govern microalgae-bacteria communities. Besides describing the in-situ abiotic dynamics of pH and oxygen within a marine diatom-bacteria biofilm system on a diel timescale, I will illustrate how these conditions, as well as added external fluctuations, can impact the chemical communication within the biofilm community using a physical-chemical numerical model with acyl-homoserine lactone signals as an example. Combining these experimental and modelled aspects, I will outline how photosynthesis-linked abiotic conditions on a micro-scale could create timed micro-niches for activities performed by the community members and therefore temporally structure processes and community functioning at a chemical level.

Primary Presenter: Christina Roggatz, University of Bremen (croggatz@uni-bremen.de)

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