anna roik


About me

My research projects aim to advance our knowledge of coral reefs. I have developed my expertise in the Caribbean, the Red Sea, and the reefs of south-east Asia, Thailand.

I study how marine ‘metaorganisms’, like reef-building corals, cope with climate change and human-made stressors. Currently, I am investigating whether we can instrumentalize the coral microbiome to enhance coral climate resilience. Developments in the field of marine probiotics play a principal role in this endeavor.

With my research I wish to advance developments of science-based remedies to the coral reef crisis.

I am also trying to preserve contemporary coral reefs and their inhabitants on my camera. You can explore my reef photo gallery where you can enjoy coral reefs from your screen at home.


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From coral microbiome functioning to probiotic applications

This project aims to advance our understanding of coral microbiome functioning and the development of ‘coral ‘probiotics’ which in the future could be used to assist acclimation under rapid climate change.

Only in the past few years climate-induced ‘coral bleaching events’ have driven significant habitat degradation in coral reefs. Science-based conservation strategies that offer sustainable and efficient solutions are urgently needed to prevent further losses.

Ocean warming is progressing too rapidly for the long-lived reef-building corals to adapt. However, the manipulation of the fast-evolving bacterial microbiome could enhance coral climate resilience within one generation.

Microbiome manipulation strategies have been successfully employed in agriculture and human medicine to tweak the health and performance of host organisms. Such approaches are also considered promising to help corals acclimatize on short times scales. A beneficial microbiome community could increase host heat tolerance through mitigation of stress at the metabolic level, however mechanisms are yet to be understood in corals.  

Topics and tools:

  • Microbiome manipulation experiments
  • Next-generation sequencing (metabarcoding and metagenomics)
  • Eco-physiological measurements (in situ measurements and coral tissue analyses)

Our first coral microbiome tranplantation experimental trials have been recently published in Microbiome Journal.

Learn about our microbiome manipulation study here in our Video Abstract!

Citation and Link:

Doering, T., Wall, M., Putchim, L. et al. Towards enhancing coral heat tolerance: a microbiome transplantation treatment using inoculations of homogenized coral tissues. Microbiome 9, 102 (2021).

This study is part of our German-Thai collaborative research projects.

We are also proud to present the Thai-language version of our video abstract! 🇹🇭

Plasticity of coral stress resilience traits

This project aims to learn about the baselines and limits of coral stress resistance. Currently, we investigate corals that live in reefs of high environmental variability in Thailand.

The endeavor of developing science-based remedies for the coral reef crisis primarily aims to enhance coral climate stress resilience and thus depends on our knowledge of the mechanisms underlying coral stress. Understanding the differences between corals that are able to efficiently resist stressors than others can teach us important lessons.

Corals and coral reef areas, where stress resistance under high temperatures has been observed, exist in many reef locations globally. Corals living under naturally fluctuating or extreme environments are likely more stress tolerant compared to conspecifics in stable environments. This has fostered the hypothesis of environmentally-mediated priming which we explore in this project. Additionally, we work on improvements of the practicability and accuracy of coral stress response assessment techniques. Such stress response assays for corals are not only vital for the study of the plasticity of stress resilience, but also urgently needed to enable rapid surveys in natural population identifying stress tolerant corals for the purposes of reef management and restoration efforts.

Topics and tools:
• Environmental priming
• High-throughput short-term heat stress assays for corals
• Coral health and fitness variables
• Reef monitoring

Coral reef functioning in the Red Sea

This project acquired several full-year, in situ data sets of physicochemical variables, macro and microbial community patterns, and reef growth in coral reefs along an environmental cross‐shelf gradient. These data enabled thorough analyses of the dynamic interplay of abiotic and biotic factors. Important seasonal baseline data and reef carbonate budgets of the reefs in the central Red Sea were delivered.

Coral reefs in the central Red Sea are sparsely studied and baseline data on physicochemical and key biotic variables are missing. Despite high temperature and salinity conditions that challenge reef growth in other oceans, the Red Sea maintains amongst the most diverse and productive coral reefs worldwide. Understanding of ecosystem functioning in this region promises to contribute novel insights of coral reefs in challenging environments and help predict coral reef trajectories under climate change consequences.
Topics and tools:
• Long-term coral reef monitoring
• Ocean sensing
• Line-intercept transects
• Coral calcification
• Carbonate budgets
• Abiotic-biotic interactions
• Bacterial ecology of coral reefs
• Coral reef biofilms
• Next-generation sequencing (metabarcoding)

Physiological plasticity of deep sea corals in the Red Sea

This project reported on the occurrence and biology of deep sea corals in the Red Sea focusing on their specific adaptation strategies which help them colonize the deep Red Sea.

The coral Eguchipsammia fistula is a cold water, aposymbiotic coral. It is a cosmopolitan species which occurs across the southern hemisphere. This research project specifically documented the occurrence of this cosmopolitan coral in the comparably warm (>20 ◦C), oxygen- and nutrient-limited deep sea habitats of the Red Sea. Its ability to cope with these specific conditions is indicative of its remarkably wide physiological plasticity, which makes the species a valuable cold water/ deep sea coral model to study mechanisms of acclimation and adaptation.

Topics and tools:
• Deep sea coral collection and cultivation
• Physiological experiments
• Health and fitness measurements
• Bacterial communities
• Next-generation sequencing

Coral bleaching in the central Red Sea

Coral reefs in the Red Sea were not spared during the 3rd global coral bleaching event in 2015/16. This project delivered observations of the benthic reef communities at the onset of the bleaching event and evaluated changes towards the end of the event in the central Red Sea.

Topics and tools:

• Coral reef bleaching surveys
• Line-intercept transects

Coral reef restoration using sexual propgules

This project investigated coral reproduction and recruitment in the reefs of the southern Caribbean island of Curaçao and established techniques of ex situ coral sexual reproduction for the critically endangered coral species Acropora palmata and A. cervicornis.

Aiming to counteract the dramatic coral and reef habitat losses of the past few decades, coral reef restoration efforts are seeking to optimize and improve techniques of coral gardening and propagation. The use of sexual propagules is one such strategy to improve the survival of coral propagules outplanted into a damaged reef. In comparison to clonal coral fragments, sexually produced recruits carry a high genetic diversity which translates into a larger pool of resilience traits and will increase the survival rates in restored populations.
Topics and tools

• Conservation of endangered the coral Acropora palmata and A. cervicornis
• Coral gamete collection (coral spawning work)
• Surveys of natural coral recruitment patterns using photo transects
• Coral larvae cultivation
• Indoor and outdoor coral nurseries
• Skeletal growth monitoring


2021 – now: HIFMBHelmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg, Germany

2017 – 2021: GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany

2016 – 2017: Christian-Albrecht University Kiel CAU, Germany

  • Postdocotral Fellow at the Institute for Microbiology
  • CRC 1182 Origin and Function of Metaorganisms Research Fellow

2012 – 2016: King Abdullah University of Science and Technology KAUST, KSA

2010 – 2012: Ruhr-University Bochum RUB, Germany


2012 – 2016: PhD Marine Science

  • King Abdullah University of Science and Technology KAUST, KSA

2007 – 2010: Master Biology and Biotechnology

  • Ruhr-University Bochum RUB, Germany

2007/08: Erasmus Scholar

  • University College Cork UCC, Republic of Ireland

2003 – 2006: B.A. Biology and English Studies

  • Ruhr-University Bochum RUB, Germany

Selected peer-reviewed research papers

For all my scientific publications please see Google Scholar

Book Chapters

  • Ziegler M, Roik A, Röthig T, Wild C, Rädecker N, Bouwmeester J, Voolstra CR (2019) Ecophysiology of Reef-Building Corals in the Red Sea. In: Voolstra CR, Berumen ML (eds.) Coral Reefs of the Red Sea, Coral Reefs of the World 11, DOI: 10.1007/978-3-030-05802-9_3

Other Publications​ and Conference Contributions


  • Roik A (2021) “Coral microbiomes and the coral reef crisis”, Invited Talk, Max-Planck-Institute for Marine Microbiology (MPI Bremen), Department of Symbiosis, 22nd April 2021
  • Roik A (2020). “First time testing of coral microbiome transplantation: A probiotic therapy to increase coral heat resilience?“, Presentation, CRC 1182 Metaorganism Seminar 26th May 2020,
  • Röthig T, Yum LK, Kremb SG, Roik A, Voolstra CR (2019) Warm water deep-sea corals – microbiome analysis provides insight into functional adaption to a unique environment. Reef Conservation UK (RCUK), 14th Dec 2019, Zoological Society of London, UK
  • Pohl N, Döring T, Wall M, Putchim L, Ratanawongwan T, Hentschel U, Roik A (2019) Differential heat tolerance of corals in the Thai Andaman Sea. ICYMARE, International Conference for Young Marine Researchers, 24-27th Sep 2019, Bremen, Germany
  • Roik A, Döring T, Putchim L, Schmidt G, Ratanawongwan T, Thontham N, Hentschel U and Wall M (2018) Bacterial contributions to the heat tolerance of coral holobionts in the Andaman Sea. In: ISME17 – 17. International Symposium on Microbial Ecology, 12.-17th Aug 2018, Leipzig, Germany
  • Döring T., Wall M, Putchim L, Ratanawongwan T, Hentschel U, Reusch TBH, Roik A (2018) Coral microbiome manipulation ‐ a new tool for enhancing coral resilience? In: CRC1182 / YIRD, 27th June 2018, Kiel, Germany
  • Roik A (2017). The role of the bacterial microbiome in acclimatization and resilience of reef‐building corals. Presentation, Advances in Integrated Ocean Research Towards Sustainable Development, University of Kiel, CAU, Germany


  • Roik A, Roder C, Röthig T, Voolstra CR (2016) Spatial and seasonal calcification in corals and calcareous crusts in a naturally warm coral reef region. In: American Geophysical Union (AGU), Ocean Sciences Meeting 2016, abstract# AH14A-001r
  • Röthig T, Ochsenkühn MA , van der Merwe R, Roik A, Voolstra CR (2016) Response of holobiont compartments to salinity changes indicates osmoregulation of scleractinian corals. In: American Geophysical Union (AGU), Ocean Sciences AMeeting 2016, abstract# PC54B-2263
  • Roik A, Röthig T, Pogoreutz C, Voolstra CR. (2016). Environmental and biotic drivers of reef growth in a central Red Sea coral reef system.  Presentation, Tarek Ahmed Juffali Workshop by Prof. C.M. Duarte and Prof. J.P. Gattuso “Tropical marine ecosystems in a high-CO2 world”, KAUST, Saudi Arabia
  • Roik A, Röthig T, Roder C, Voolstra CR. (2015). Seasonal and spatial trends of calcification in the central Red Sea. Presentation, Coral Reefs of Arabia, New York University Abu Dhabi, UAE
  • Roik A, Röthig T, Roder C, Voolstra CR. (2015). Seasonal and spatial reef calcification in corals and calcareous crusts in the central Red Sea. Poster Presentation, Red Sea Research Center – Student & Postdoc Poster meeting, KAUST, Saudi Arabia
  • Roik A, Rothig T, Roder C, Voolstra CR. (2014). Biological drivers of reef formation in the Central Red Sea. Presentation, International Conference on the Marine Environment of the Red Sea (ICMERS), King Abdulaziz University (KAU),  Saudi Arabia
  • Roik A, Röthig T, Roder C, Voolstra CR. (2013). Carbonate budgets in the Red Sea: Temporal and spatial trends of reef accretion in exceptional marine environments. Presentation, 4th Young Reef Scientists Meeting (YRMS), Justus-Liebig University, Giessen, Germany
  • Roik A, Petersen D, Brittsan M, Tollrian R. (2012). Coral reef restoration based on sexual coral reproduction. Presentation, 12th international Coral Reef Symposium (ICRS), Cairns, Australia
  • Petersen D, Roik A, Brittsan M, Tollrian R. (2010). SECORE Acropora restoration project. Presentation, European Coral Reef Symposium (ISRS), Wageningen, The Netherlands
  • Geomar News (2018) Die Baumeister der Ozeane. Geomar Newsletter 2018|03

  • KAUST Discovery (2018) Understanding the growth of coral reefs. Article 778

  • Sarant L (2018) Red Sea reef growth could point to global trends. Nature Middle East. Doi:10.1038/nmiddleeast.2018.137