Alexandra Kroll

Dr. Alexandra Kroll

About Me

Current research

Effects of anthropogenic stressors to periphyton

Periphyton is a taxonomically diverse and dynamic biofilm-forming community of heterotrophic and phototrophic microorganisms that contribute among others to primary production and nutrient spiralling in streams and are thus an essential element of stream ecosystems.

In essence, these biofilms are an incredibly rich resource as community model - and beautiful at the same time.

Stressors, that adversely affect biofilm organisms and thus impact their ecosystem functions, indirectly affect the periphyton-dependent biocenosis. Structural changes in periphyton that do not immediately change productivity may alter the impact of subsequent disturbances. However, the complexity and dynamics of the biofilms poses a challenge to identifying sensitive descriptors, a useful level of resolution, and linking observed changes to understand underlying mechanisms.

Against this background, we work on characterizing periphyton on different levels of resolution, going from the overall 3D structure (CLSM), extracellular polymeric substances (EPS), and the genetic diversity of selected algae groups (community fingerprinting by automated ribosomal intergenic spacer analysis [ARISA]), down to individual cellular morphology (by Flow cytometry) and sequences of selected genomic regions. These descriptors are combined with standard summative parameters (biomass, photosynthetic activity) and species identification by light microscopy.

We have designed an indoor facility for cultivation and exposure of biofilms, which allows manipulation of essential environmental parameters such as light intensity, flow velocity, temperature, and water chemistry.

We currently use this approach to assess effects of model pesticides as well as synthetic nanoparticles.

Furthermore, we study the fate of nanoparticles within the biofilms, and the interaction of nanoparticles with extracellular polymeric substances (EPS) secreted by periphytic organisms.
We apply DLS (dynamic light scattering), NTA (nanoparticle tracking analysis), electron microscopy, spectrophotometry, CLSM (confocal laser scanning microscopy), ICP-MS (inductively coupled plasma mass spectrometry), and surface-enhanced Raman spectroscopy for NP detection and characterization.

Other topics I am personally interested in - and partially colaborate on - are artificial photosynthesis, atmospheric pollution, and normative aspects in natural sciences.

Research partners

Effects of engineered nanoparticles:

Dr Marianne Matzke, Dr Claus Svendsen - CEH Wallingford, UK

Prof Dr Thomas Backhaus - University of Gothenburg, S

Dr Marcus Rybicki, Dr Dirk Jungmann - Technical Unvirsity of Dresden

Quantification of changes in biofilm community structure and diversity:

Dr Anze Zupanic - Eawag Dübendorf, CH

Intra- and extracellular detection and characterization of engineered nanoparticles:

Dr Martin Wiemann - IBE R&D gGmbH Münster, D

Thorsten Wagner, Prof Dr Hans-Gerd Lipinski - University of Applied Science and Arts Dortmund, D

Interaction of engineered nanoparticles with EPS:

Dr Andreas Borgschulte - Empa Dübendorf, CH

Use of biofilms in photocells:

Dr Arthur Braun - Empa Dübendorf, CH

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Interdisciplinary project on biological effects of urban micropollutants

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Curriculum Vitae

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Phone: +41 58 765 5487
Fax: +41 58 765 5802
Address: Eawag
Überlandstrasse 133
8600 Dübendorf
Office: FX E23

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