Project A03

Functional and compositional responses of stream microphytobenthic communities to multiple stressor increase and decrease

Hypothesis 1 Hypothesis 1 Hypothesis 1 ARC 2 ExStream Field studies Protists, autotroph

Project leader

Prof. Dr. Bánk Beszteri

Project Summary

Microphytobenthos represents the main autochtonous source of organic matter in stream ecosystems, and is characterised by a rich organismal diversity. Diatoms are arguably the best-studied organisms in these communities: compositional differences of their assemblages along diverse environmental gradients, including anthropogenic stressors, have been described in a range of systems. Effects of anthropogenic stressors upon photosynthetic fitness and performance of stream microphytobenthic communities have also been studied (though less frequently).

An integrative characterisation of community reorganisations and changes in photosynthesis-related traits accompanying stressor load and release under highly controlled conditions has, however, rarely been attempted. This project aims, on the one hand, to fill this gap by assessing compositional responses (by microscopy and DNA metabarcoding) in parallel with functional changes (in photosynthesis-related traits) of microphytobenthos to stressor increase and release in the ExStream experiments of RESIST.

Second, participating in the field activities of the CRC by characterizing field microphytobenthic communities in an analogous manner, the project will assess to what extent differences in these communities reflect differences in land use (in the Kinzig network) and differing time periods since stream restoration (in the Emscher/Boye localities). Beyond establishing community ecological foundations for benthic microalgae (and other protists) in the study sites, the first project phase will mainly address the hypothesis that photosynthesis related traits are largely decoupled from community composition under moderate stressor levels.

Complementing results of other RESIST projects, our data sets will contribute to comparative analyses among different organismal groups within the synthesis activities in the frame of Z03. At this level, the data from this project will help to address the hypothesis that because of their larger population sizes and resulting better dispersability, microph