BS-PortraitBettina Sonntag


Present position:

Senior scientist
Head of working group "Ciliate ecology and taxonomy"

Research area:

Protist ecology, biodiversity and taxonomy in lakes



+43 512 507-50243

Employment History · Research · Staff · Projects · Publications · Awards · Editorial Board

Employment History

  • September 1, 2012 – present:
    Senior Scientist
    at the Research Department for Limnology, Mondsee of the Leopold-Franzens-University of Innsbruck (LFUI) and head of the research group ‘Ciliate ecology and taxonomy’
  • 2011 – August 31, 2012:
    Senior Scientist at the Institute for Limnology of the Austrian Academy of Sciences and head of the research group ‘Ciliate ecology and taxonomy’
  • 2000 – 2011:
    Post Doc
    Research Associate at the Institute of Ecology at the LFUI

  • 2000:
    Guest researcher
    at the Institute of Zoology in the Lab of Prof. Wilhelm Foissner, University of Salzburg, Austria

  • 1998 – 2000:
    Doctoral thesis
    at the Institute of Zoology & Limnology at the LFUI

  • 1990 – 1998:
    Diploma in Biology at the Institute of Zoology & Limnology at the LFUI



Our research group focuses on protist ecology, biodiversity and taxonomy in lakes. To understand the autecology of especially ciliates in planktonic food webs, we study these protists on an alpha-taxonomic level including morphological, molecular and ecological approaches. We also focus on microbiomes especially in mixotrophic algal-bearing ciliates. For details and ongoing research projects see

Organisation team



FG Sonntag

FG Sonntag, v.l.n.r.: B. Sonntag, N. Gogoleva, U. Koll, A. Potekhin, C. Spanner,
T. Pröschold, M. Juti Owuor, J. Kannler, Foto: S. Wanzenböck

Former members

  • Mario Aigner (2021, MSc)  "Fraßdruck von Fischlarven aus dem Coregonus lavaretus Artenkomplex auf Ciliaten", supervision together with Wanzenböck, J.

  • Fabian Sommer (2021, MSc) "Man-made mountain reservoirs: ciliates in human-influenced habitats", supervision together with Tartarotti, B.

  • Daniela Frantal (2020, MSc) "Integrative taxonomy: morphology and molecular phylogeny of the genus Urotricha (Prostomatida, Ciliophora)", supervision together with T. Pröschold

  • Christian Spanner (2019, MSc) "Endosymbiotische Süßwasseralgen und ihr Ciliaten-Wirt Paramecium bursaria: Morphologie, Phylogenie und Ökologie", supervision together with T. Pröschold

  • Anna Binder (2019, MSc) "Identification of indicator ciliates (Ciliophora, Alveolata) in water quality assessment: an integrative approach", supervision together with T. Pröschold

  • Daniel Rieser (2019, MSc)  "Systematik, Morphologie und molekulare Phylogenie der Gattung Coleps (Prostomatea, Ciliophora) und deren Endosymbionten, supervision together with T. Pröschold

  • Laura Nachbaur (2017, Diplom) "Planktonciliaten als Modellorganismen im mikrobiellen Nahrungsnetz des Mondsees. Das Leben im Wassertropfen forschend erlernen" supervision together with B. Kammerlander

  • Barbara Kammerlander (2017, PhD) "Diversity and ecology of ciliate communities in alpine lakes of contrasting transparency", supervision together with R. Sommaruga

  • Daniela Pöll (2014, MSc) "UV-Schutzstrategien des heterotrophen Süßwasserciliaten Balanion planctonicum"

  • Geoffrey Ong’ondo (2014, PhD) "Molecular microbial eukaryote diversity in five Rift Valley lakes and description of three ciliate species from Lake Bogoria, Kenya" supervised together with J. Boenigk



  • Concert of trumpets: next generation taxonomy of Stentor - FWF PAT 8010623 (Jan 2024-Oct 2027)

  • Next Generation Taxonomy: Ciliophora and their bacterial symbionts as a proof of concept - EU - Horizon 2020 Marie Curie Actions - Research and Innovation Staff Exchange (RISE) University of Pisa, Italy, PI Giulio Petroni (Jul 2021-Jun 2025)

  • Aquatic Symbiosis Genome Project, Subhub of PI P. Keeling (University of British Columbia) ‘Ciliates as models for symbiosis: using genomic analyses of functionally diverse symbiotic associations with parallel origins to gain insights into basic evolutionary principles of symbiosis’ – Wellcome Sanger Institute and Gordon and Betty Moore Foundation (started in Oct 2020)

  • Pan-European Lake Sampling - Microbial Eco-genomics Czech Academy of Sciences, Biology Centre CAS, Budweis, Czech Republic; PI Rohit Ghai, Michaela Salcher (Jan 2020 – Dec 2024)

  • Freshwater endosymbiotic algae and their ciliate hosts: morphology, phylogeny, ecology - FWF P 28333-B25 (Apr 2016 - Mar 2021)

  • Co-occurrence networks in aquatic food webs: ciliates as models, D-A-CH funded by the FWF = Lead Agency, I22380-B25  (Sept 2015 - Sept 2020)

  • ‘Ultraviolet radiation effects on planktonic freshwater ciliates: an assessment of photoprotection and repair strategies’  (FWF), P21013-B03, Feb 2009 – Nov 2013





  • Spanner C., Darienko T., Filker S., Sonntag B., Pröschold T. (2022). Morphological diversity and molecular phylogeny of five Paramecium bursaria (Alveolata, Ciliophora, Oligohymenophorea) syngens and the identification of their green algal endosymbionts, Scientific Reports 12: 18089, doi: 10.1038/s41598-022-22284-7

  • Sommer F., Sonntag B., Rastl N., Summerer M., Tartarotti B. (2022). Ciliates in man-made mountain reservoirs. Front. Environ. Sci. 10:903095. doi: 10.3389/fenvs.2022.903095

  • Sonntag B., Frantal D., Kammerlander B., Darienko T., Filker S., Stoeck T., Gruber M., Pröschold T. (2022). Widespread occurrence of two planktonic ciliate species (Urotricha, Prostomatida) originating from high mountain lakes. Diversity 14, 362

  • Frantal D., Agatha S., Beisser D., Boenigk J., Darienko T., Dirren-Pitsch G., Filker S., Gruber M., Kammerlander B., Nachbaur L., Scheffel U., Stoeck T., Qian K., Weißenbacher B., Pröschold T., Sonntag B. (2022). Molecular data reveal a cryptic diversity in the genus Urotricha (Alveolata, Ciliophora, Prostomatida), a key player in freshwater lakes, with remarks on morphology, food preferences, and distribution. Front. Microbiol. 12:787290. doi: 10.3389/fmicb.2021.787290


  • Qu Z., Forster D., Bruni E., Frantal D., Kammerlander B., Nachbaur L., Pitsch G., Posch T., Pröschold T., Teubner K., Sonntag B., Stoeck T. (2021). Aquatic food webs in deep temperate lakes: key species establish through their autecological versatility. Molecular Ecology 30(4):1053-1071, doi.10.1111/mec.15776

  • Pröschold T., Rieser D., Darienko T., Nachbaur L., Kammerlander B., Qian K., Pitsch G., Bruni P., Qu Z., Forster D., Rad-Mendez C., Posch T., Stoeck T., Sonntag B. (2021).  An integrative approach sheds new light onto the systematics and ecology of the widespread ciliate genus Coleps (Ciliophora, Prostomatea). Sci Rep 11: 5916,

  • Forster D., Qu Z., Pitsch G., Bruni E.P., Kammerlander B., Pröschold T., Sonntag B., Posch T., Stöck T. (2021). Lake ecosystem robustness and resilience inferred from a climate-stresses protistan plankton network. Microorganisms 9: 549, doi: 10.3390/microorganisms9030549


  • Sonntag B., Sommaruga R. (2020). Effectiveness of Photoprotective Strategies in Three Mixotrophic Planktonic Ciliate Species. Diversity 12:252, doi.10.3390/d12060252

  • Spanner C., Darienko T., Biehler T., Sonntag B., Pröschold T. (2020). Endosymbiotic green algae in Paramecium bursaria: A new isolation method and a simple diagnostic PCR approach for the identification, Diversity 12(6):240 doi:10.3390/d12060240


  • Pitsch G., Bruni E.P., Forster D., Qu Z., Sonntag B., Stoeck T., Posch T.  (2019). Seasonality of planktonic freshwater ciliates: are analyses based on V9 regions of the 18S rRNA gene correlated with morphospecies counts? Frontiers in Microbiology: Aquatic Microbiology 10:248. doi: 10.3389/fmicb.2019.00248


  • Kammerlander B., Tartarotti B., Sonntag B. (2018). The impact of UV radiation on Paramecium populations from alpine lakes. Journal of Eukaryotic Microbiology 65(2):250-254, doi. 10.1111/jeu.12463


  • Schabetsberger R., Sichrowsky U., Scheck A., Schagerl M., Mähnert B., Sonntag B., Pall K. (2017). First limnological characterization of the crater-lake Billy Mitchell (Bougainville Island, Papua New Guinea). Pacific Science 71:29 – 45

  • Sonntag B, Kammerlander B, Summerer M (2017). Bioaccumulation of ultraviolet sunscreen compounds (mycosporine-like amino acids) by the heterotrophic freshwater ciliate Bursaridium living in alpine lakes. Inland Waters 7:1, 55-64 doi 10.1080/20442041.2017.1294348


  • Sonntag B. (2016). Unseen worlds: microscopic lake plankton fuel food chains and befriend algae. Scientia PDF

  • Kammerlander B., Koinig K.A., Rott E., Sommaruga R., Tartarotti B., Trattner F., Sonntag B. (2016). Ciliate community structure and interactions within the planktonic food web in two alpine lakes of contrasting transparency. Freshwater Biology doi:10.1111/fwb.12828

  • Slaveykova V., Sonntag B., Gutiérrez J.C. (2016). Stress and Protists: No life without stress. European Journal of Protistology 55:39-49. doi:10.1016/j.ejop.2016.06.001

  • Weisse T., Sonntag B. (2016). Ciliates in planktonic food webs: communication and adaptive response. In: Witzany, G. & Nowacki, M. (eds), Biocommunication of ciliates. Spinger, Berlin, pp. 351-372.


  • Dunthorn M, Lipps JH, Dolan JR, Abboud-Abi Saab M, Aescht E, Bachy C, Barría de Cao MS, Berger H, Bourland WA, Choi JK, Clamp J, Doherty M, Gao F, Gentekaki E, Gong J, Hu X, Huang J, Kamiyama T, Johnson MD, Kammerlander B, Kim SY, Kim Y-O, la Terza A, Laval-Peuto M, Lipscomb D, Lobban CS, Long H, Luporini P, Lynn DH, Macek M, Mansergh RI, Martín-Cereceda M, McManus GG, Montagnes DJS, Ong’ondo GO, Patterson DJ, Pérez-Uz B, Quintela-Alonso P, Safi LSL, Santoferrara LF, Sonntag B, Song W, Stoeck T, Stoecker DK, Strüder-Kypke MC, Trautmann I, Utz LRP, Vallesi A, Vd’ačný P, Warren A, Weisse T, Wickham SA, Yi Z, Zhang W, Zhan Z, Zufall R, Agatha S (2015). Ciliates  – protists with complex morphologies and ambiguous early fossil record. Marine Micropaleontology 119:1-6. Abstract

  • Sichrowsky U., Schabetsberger R., Pall K., Sonntag B., Stoyneva M., Kalfatak D., Økland F., Scheck A., Tambets M. (2015). Limnological characterization of the largest freshwater lake in remote Oceania (Lake Letas, Gaua Island, Vanuatu). Pacific Science 69:165-180. Early view

  • Kammerlander B., Breiner H.-W., Filker S., Sommaruga R., Sonntag B., Stoeck T. (2015). High diversity of protistan plankton communities in remote high mountain lakes in the European Alps and the Himalaya mountains. FEMS Microbiology Ecology 91: fiv010. doi: 10.1093/femsec/fiv010  PDF


  • Sichrowsky U., Schabetsberger R., Sonntag B., Stoyneva M., Maloney A.E., Nelson D.B., Richey J.N., Sachs J.P. (2014) Limnological characterization of volcanic crater lakes on Uvea Island (Wallis and Futuna, South Pacific). Pacific Science 68: 333-343 doi:10.2984/68.3.3

  • Stoeck T, Breiner H-W, Filker S, Ostermaier V, Kammerlander B, Sonntag B (2014) A morpho-genetic survey on ciliate plankton from a mountain lake pinpoints the necessity of lineage-specific barcode markers in microbial ecology. Environ Microbiol 16: 430-444. PDF


  • Ong'ondo GO, Yasindi AW, Oduor SO, Jost S, Schagerl M, Sonntag B, Boenigk J 2013 Ecology and community structure of ciliated protists in two alkaline-saline Rift Valley lakes in Kenya with special emphasis on Frontonia. J Plankton Res. 35: 759-771 doi: 10.1093/plankt/fbt044


  • Sonntag B, Summerer M, Sommaruga R 2011 Are freshwater mixotrophic ciliates less sensitive to solar UV radiation than heterotrophic ones? J Euk Microbiol 58: 196-202 PDF

  • Sonntag B, Summerer M, Sommaruga R 2011 Factors involved in the distribution pattern of ciliates in the water column of a transparent alpine lake. J Plankton Res 33: 541-546 PDF Cover


  • Sommaruga R, Sonntag B 2009 Photobiological aspects of the mutualistic association between Paramecium bursaria and Chlorella. In: Endosymbionts of Paramecium (M Fujishima, Ed.), Microbiology Monographs 12, Springer Verlag, Berlin, Germany, 111-130 PDF

  • Summerer M, Sonntag B, Hörtnagl P, Sommaruga R 2009 Symbiotic ciliates receive protection against UV damage from their algae: A test with Paramecium bursaria and Chlorella. Protist 160: 233-243 mail


  • Sonntag B, Strüder-Kypke MC, Summerer M 2008 Uroleptus willii nov. sp., a euplanktonic freshwater ciliate (Dorsomarginalia, Spirotrichea, Ciliophora) with algal symbionts: morphological description including phylogenetic data of the small subunit rRNA gene sequence and ecological notes. Denisia 23: 279-288 PDF

  • Summerer M, Sonntag B, Sommaruga R 2008 Ciliate-symbiont specificity of freshwater endosymbiotic Chlorella (Trebouxiophyceae, Chlorophyta). J Phycol 44: 77-87 mail


  • Sonntag B, Summerer M, Sommaruga R 2007 Sources of mycosporine-like amino acids in planktonic Chlorella-bearing ciliates (Ciliophora). Freshwater Biol 52: 1476-1485 PDF

  • Summerer M, Sonntag B, Sommaruga R 2007 An experimental test of the symbiosis specificity between the ciliate Paramecium bursaria and strains of the unicellular green alga Chlorella. Environ Microbiol 9: 2117-2122 PDF

  • Posch T, Mindl B, Horňák K, Jezbera J, Salcher MM, Sattler B, Sonntag B, Vrba J, Šimek K 2007 Biomass reallocation within freshwater bacterioplankton induced by manipulating phosphorous availability and grazing. Aquat Microb Ecol 49: 223-232 PDF

  • Salcher MM, Hofer J, Horňák K, Jezbera J, Sonntag B, Vrba J, Šimek K, Posch T 2007 Modulation of microbial predator-prey dynamics by phosphorous availability. Part II: Growth patterns and survival strategies of bacterial phylogenetic clades. FEMS Microbiol Ecol 60: 40-50 PDF


  • Sonntag B, Posch T, Klammer S, Teubner K, Psenner R 2006 Phagotrophic ciliates and flagellates in an oligotrophic deep alpine lake: contrasting variability with seasons and depths. Aquat Microb Ecol 43: 193-207 PDF

  • Pérez P, Libkind D, Diéguez MdC, Summerer M, Sonntag B, Sommaruga R, van Broock M, Zagarese HE 2006 Mycosporines from freshwater yeasts: a trophic cul-de-sac? Photochem Photobiol Sci 5: 25-30 PDF

  • Rott E, Füreder L, Schütz C, Sonntag B, Wille A 2006 Species coexistence in contrast to competition – first evidence from biota within an extreme stream microhabitat. Proceedings of the International Association of Theoretical and Applied Limnology (SIL) 29: 2321-2323 PDF


  • Mindl B, Sonntag B, Pernthaler J, Vrba J, Psenner R, Posch T 2005 Effects of phosphorus loading on interactions of algae and bacteria: reinvestigation of the „phytoplankton-bacteria paradox“ in a continuous cultivation system. Aquat Microb Ecol 38: 203-213 PDF


  • Sonntag B, Foissner W 2004 Urotricha psenneri n. sp. and Amphileptus piger (Vuxanovici, 1962) n. comb., two planktonic ciliates (Protozoa, Ciliophora) from an oligotrophic lake in Austria. J Eukaryot Microbiol 51: 670-677 mail


  • Sonntag B, Posch T, Klammer S, Griebler C, Psenner R 2002 Protozooplankton in the deep oligotrophic Traunsee (Austria) influenced by discharges of soda and salt industries. Water, Air, and Soil Pollution: Focus 2: 211-226 mail

  • Griebler C, Sonntag B, Mindl B, Posch T, Klammer S, Psenner R 2002 Assessment of the ecological integrity of Traunsee (Austria) via analysis of sediments and benthic microbial communities. Water, Air, and Soil Pollution: Focus 2: 33-62 mail

  • Klammer S, Posch T, Sonntag B, Griebler C, Mindl B, Psenner R 2002 Dynamics of bacterial abundance, biomass, activity, and community composition in the oligotrophic Traunsee and the Traun River (Austria). Water, Air, and Soil Pollution: Focus 2: 137-163 mail


  • Posch T, Jezbera J, Vrba J, Šimek K, Pernthaler J Andreatta S, Sonntag B 2001 Size selective feeding in Cyclidium glaucoma (Ciliophora, Scuticociliatida) and its effects on bacterial community structure: a study from a continuous cultivation system. Microb Ecol 42: 217-227 PDF


  • Sonntag B, Posch T, Psenner R 2000 Comparison of three methods for determining flagellate abundance, cell size, and biovolume in cultures and natural freshwater samples. Arch Hydrobiol 149: 337-351 mail


  • Wille A, Sonntag B, Sattler B, Psenner R 1999 Abundance, biomass and size structure of the microbial assemblage in the high mountain lake Gossenköllesee (Tyrol, Austria) during the ice-free period. J Limnol 58: 117-126 PDF

  • Posch T, Šimek K, Vrba J, Pernthaler J, Nedoma J, Sattler B, Sonntag B, Psenner R 1999 Predator-induced changes of bacterial size-structure and productivity studied on an experimental microbial community. Aquat Microb Ecol 18: 235-246 PDF

  • Pfister G, Sonntag B, Posch T 1999 Comparison of a direct live count and an improved quantitative protargol stain (QPS) in determining abundance and cell volumes of pelagic freshwater protozoa. Aquat Microb Ecol 18: 95-103 PDF

Popular scientific contributions

  • Sonntag B 2010 „Hochalpiner Sonnenschutz“ (Zukunft Forschung, 01/10, p. 14-15) PDF



  • 2010 Award of the ‘Foundation of the South Tyrolian Savings Bank’ dedicated to R. Sommaruga for the publication: Sommaruga R, Sonntag B 2009 Photobiological aspects of the mutualistic association between Paramecium bursaria and Chlorella. In: Endosymbionts of Paramecium (M Fujishima, Ed.), Microbiology Monographs 12, Springer Verlag, Berlin, Germany, 111-130

  • 2009 ‘Kanadapreis’ of the ‘Canadian studies centre of the LFUI’ for the publication: Sonntag B, Strüder-Kypke MC, Summerer M 2008 Uroleptus willii nov. sp., a euplanktonic freshwater ciliate (Dorsomarginalia, Spirotrichea, Ciliophora) with algal symbionts: morphological description including phylogenetic data of the small subunit rRNA gene sequence and ecological notes. Denisia 23: 279-288

  • 2007 Award of the ‘Theodor Körner Fonds zur Förderung von Wissenschaft und Kunst der Kammer für Arbeiter und Angestellte’ for the project ‚Ciliates in Piburgersee’

  • 2006 Special science award of the province of Vorarlberg, Austria

  • 2006 Grant for my Ph.D. thesis from the province of Vorarlberg

  • 2005 ‘Dr. Otto-Seibert-Award to fund scientific publications at the LFUI’ for the publication: Sonntag B, Foissner W 2004 Urotricha psenneri n. sp. and Amphileptus piger (Vuxanovici, 1962) n. comb., two planktonic ciliates (Protozoa, Ciliophora) from an oligotrophic lake in Austria. J Eukaryot Microbiol 51: 670-677


Editorial Board

Frontiers in Microbiology


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