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Dr. Elias Ehrlich


Campus Botanischer Garten
University of Potsdam
Ecology and Ecosystem Modelling
Maulbeerallee 2, building 2
14469 Potsdam

Guest scientist at Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB)

Research Interests

I am an aquatic ecologist and ecological modeler who has a large interest in solving major conservation problems in socio-ecological systems. I focus on aquatic systems, including dynamics of individuals, species populations and entire food webs (ranging from plankton organisms to fish) and their link to humans as resource users and drivers of environmental change. To address major conservation problems (e.g. biodiversity loss, overharvesting, invasive species or toxic algal blooms), I work with quantitative models and use stakeholder knowledge to develop new ecological theory and inform decision making in conservation and ecosystem management.

My recent research can be summarized in four main topics:

1. The role of trade-offs for maintenance of biodiversity and ecosystem functions under environmental change

I have developed novel ecological theory on how trade-offs between functional traits and their specific shape affect biodiversity (Ehrlich et al. 2017, Ecology; Ehrlich & Gaedke 2018, Ecology and Evolution), community trait dynamics (Ehrlich et al. 2020, ISME) and ecosystem functions (Ehrlich et al., in prep.) under altered environmental conditions applied to plankton systems. In the future, I want to extend this trade-off theory to the individual level and study how behavioral decision and phenotypic plasticity constrained by specific trade-off shapes respond to environmental change and how these processes at the individual level affect then the overall food web dynamics and biodiversity.

2. Stakeholder-inclusive management processes and conservation projects

I am very interested in designing and facilitating adaptive management processes that make use of practical knowledge of stakeholders and give them power to make decision based on well-communicated scientific insights derived from experiments, field studies and modelling (Ehrlich et al. 2023, Fisheries Research). In a recent project on northern pike (Esox lucius) in the southern Baltic Sea, called BODDENHECHT, we gained insights on ecological and socio-economic factors and interactions in a fisheries system that directly flowed into a process of structured decision making where I took the lead, facilitated the workshops and contributed modelling forecasts on management options.

3. Dynamics of toxic phytoplankton blooms

Toxic phytoplankton blooms have increased in frequency and expansion in many waterbodies worldwide, with well-known negative impacts on human health, fisheries and ecosystem functions. I am interested in understanding of what drives the dynamics of toxic phytoplankton blooms under altered environmental conditions and what affects their toxicity related to the frequently observed coexistence of toxic and non-toxic genotypes within such blooms. In a recent study, we found that this intraspecific variation in toxicity and coexistence of different genotypes can be understood based on individual-level demographic processes generating patchiness in such blooms (Ehrlich et al. 2022, Proceeding of the Royal Society B: Biological Science). I used an innovative individual-based phytoplankton model to reveal mechanisms generating small-scale spatial heterogeneity in toxic algal blooms, which in turn crucially affect the coexistence of genotypes. In the future, I want to extend the use of individual-based models in plankton ecology to further study the role of spatial heterogeneity for community dynamics and maintenance of biodiversity.

4. Aquatic systems as model systems to understand broader questions related to biodiversity and maintenance of ecosystem functions under global change

In a previous project, I have used lake plankton data to understand how trait changes at one trophic level affect biomass and trait dynamics on other trophic levels in plankton, which resulted in a new concept called “trophic biomass-trait cascade” that can be applied across ecosystems (Ehrlich & Gaedke 2020, Limnology and Oceanography). In the future, I want to study trait and biomass dynamics not only within plankton but also up to trophic levels of fish and to link the system also to terrestrial systems, for example, by including predatory birds like cormorants (Arlinghaus et al. 2023). Furthermore, I see much potential to connect food web dynamics to socio-economic systems like fisheries, which have a direct influence on top-predators and feedback with their resource (Dao et al. 2023, Fisheries Research).


Campus Botanischer Garten
University of Potsdam
Ecology and Ecosystem Modelling
Maulbeerallee 2, building 2
14469 Potsdam

Guest scientist at Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB)

Scientific career

Since 2023         PostDoc,  University of Potsdam

Since 2023         Guest scientist at Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin

2021 – 2023        PostDoc at Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) within the BODDENHECHT Project, Berlin

2020 – 2021       PostDoc at University of Potsdam

2019 – 2020       PostDoc at Centre for Ocean Life at the Technical University of Denmark (DTU) and at University of Potsdam

2015 – 2019      PhD student in the DynaTrait project supervised by Ursula Gaedke, thesis title: “On the Role of Trade-offs in Predator-Prey Interactions”, University of Potsdam

2015                    Master in Ecology, Evolution and Conservation, University of Potsdam


Three key publications:

  • Ehrlich, E., A. Bath, D. Niessner, D. Koemle, E.-M. Cyrus and R. Arlinghaus (2023). Codesigning management recommendations with stakeholders: a case study about northern pike(Esox lucius) in the southern Baltic Sea. Fisheries Research, 263: 106687. DOI: 10.1016/j.fishres.2023.106687.
  • Ehrlich, E., U. H. Thygesen and T. Kiørboe (2022). Evolution of toxins as a public good in phytoplankton. Proceeding of the Royal Society B: Biological Science, 289: 20220393. DOI: 10.1098/rspb.2022.0393.
  • Ehrlich, E., N. J. Kath and U. Gaedke (2020). The shape of a defense-growth trade-off governs  seasonal trait dynamics in natural phytoplankton. ISME Journal, 14: 1451–1462. DOI: 10.1038/s41396-020-0619-1

Further publications:

  • Rittweg, T. D.,  C. Trueman, E. Ehrlich, M. Wiedenbeck and R. Arlinghaus (2023). Corroborating otolith age using oxygen isotopes and comparing outcomes to scale age: Consequences for estimation of growth and reference points in northern pike (Esox lucius). Fisheries Management and Ecology, 00: 1–16. DOI: 10.1111/fme.12646
  • Arlinghaus, R., T. Rittweg, F. Dhellemmes, D. Koemle, R. van Gemert, H. Schubert, D. Niessner, S. Möller, J. S. Droll, R. Friedland, W.-C. Lewin, M. Dorow, L. Westphal, E. Ehrlich, H.V. Strehlow, M.S. Weltersbach, P. Roser, M. Braun, F. Feldhege and H. Winkler (2023). A synthesis of a coastal northern pike (Esox lucius) fishery and its social-ecological environment in the southern Baltic Sea: Implications for the management of mixed commercial-recreational fisheries. Fisheries Research, 263: 106663. DOI: 10.1016/j.fishres.2023.106663
  • Dao, T., M. Quaas, D. Koemle, E. Ehrlich and R. Arlinghaus (2023). Can price feedback cause human behavior-induced tipping points in exploited stocks? An extension of the bioeconomic Gordon-Schaefer model. Fisheries Research, 259: 106550. DOI: 10.1016/j.fishres.2022.106550
  • Ehrlich, E., N.J. Kath and U. Gaedke (2022). Fraßschutz auf Kosten des Wachstums – wie die Form eines Trade-offs die Jahresdynamik von funktionellen Phytoplanktoneigenschaften steuert. Korrespondenz Wasserwirtschaft, 15 (4): 212-217. DOI: 10.3243/kw2022.04.001
  • Arlinghaus, R., A. Vogt, D. Koemle, D. Niessner, E. Ehrlich, T. Rittweg and J. Droll (2022). Ursachenanalyse von Berufsfischer-Angler Konflikten am Beispiel der Nutzung von Hechten (Esox lucius) in den Boddengewässern Mecklenburg-Vorpommerns. Zeitschrift für Fischerei, 2 (Artik. 2): 1–27. DOI: 10.35006/fischzeit.2022.10
  • Ehrlich, E., and U. Gaedke (2020). Coupled changes in traits and biomasses cascading through a tritrophic plankton food web. Limnology and Oceanography, 65 (10): 2502-2514. DOI: 10.1002/lno.11466
  • Ehrlich, E., and U. Gaedke (2018). Not attackable or not crackable - How pre- and post-attack defenses with different competition costs affect prey coexistence and population dynamics. Ecology and Evolution, 8: 6625-6637. DOI: 10.1002/ece3.4145
  • Ehrlich, E., L. Becks, and U. Gaedke (2017). Trait-fitness relationships determine how trade-off shapes affect species coexistence. Ecology, 98 (12): 3188–3198. DOI: 10.1002/ecy.2047

Book and management plan:

  • Arlinghaus, R., M. Braun, F. Dhellemmes, E. Ehrlich, F. H. Feldhege, D. Koemle, D. Niessner, J. Palder, J. Radinger, C. Riepe, P. Roser, T. D. Rittweg and H. Winkler (2023): BODDENHECHT – Ökologie, Nutzung und Schutz von Hechten in den Küstengewässern Mecklenburg-Vorpommerns. Berichte des IGB, Band 33, 796 Seiten. DOI: 10.4126/FRL01-006453300
  • Ehrlich, E., D. Niessner and R. Arlinghaus (2023). Empfehlungen für das künftige Management des Boddenhechts (Esox lucius) aus Sicht verschiedener Interessensgruppen. DOI: 10.3126/FRL01-0064447477

Selected talks and conference contributions

  • Talk: “Managementempfehlungen aus Sicht der Interessengruppen - Ergebnisse der Runden Tische“ (2023). Final event of BODDENHECHT project with handover of management advices on pike to responsible ministry, Stralsund, Germany
  • Talk: “Managing Baltic pike – A participatory modelling approach as a decision tool for future harvest regulations” (2021). Baltic Pike Symposium, Berlin, Germany
  • Talk: “Evolution of toxins as a public good in phytoplankton” (2020). Annual DynaTrait Meeting, Potsdam, Germany
  • Invited talk: “On the role of trade-offs in predator-prey interactions” (2019) at the Centre for Ocean Life, DTU Lyngby, Denmark
  • Talk: “Trait-fitness relationships determine how trade-off shapes affect species coexistence” (2018). Models in Population Dynamics, Ecology, and Evolution (MPDEE’18), Leicester, UK
  • Talk: “Trait-fitness relationships determine how trade-off shapes affect species coexistence” (2017) at the Centre for Ocean Life, DTU Lyngby, Denmark
  • Poster: “Seasonal trait coupling of phyto- and zooplankton in Lake Constance – data and models” (2017). International DynaTrait Conference, Hannover, Germany
  • Poster: “Key properties of trade-offs affecting coexistence and population dynamics” (2017). Workshop on trait-based approaches to ocean life, Bergen, Norway
  • Talk: “Multidimensional Trade-offs and Coexistence” (2016). Experimental Evolution & Community Dynamics Minisymposium, Plön, Germany
  • Poster: “The shape of trade-offs determines long- and short-term maintenance of functional diversity” (2016). European Conference on Mathematical and Theoretical Biology (ECMTB), Nottingham, UK
  • Talk: “Biodiversity effects in phytoplankton communities – combining experiments and modelling” (2013). Annual meeting of the German Limnological Society (DGL) and of the Ecological Society of Germany, Austria and Switzerland (GfÖ), Potsdam, Germany