The heat is on: resilience and tipping points in Arctic phytoplankton populations under climate change induced heatwaves

• Applicant: Dr. Klara Wolf
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems ; Oceanography
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 442160768

• Final Report Year: 2024

Final Report Abstract

Extreme events like marine heatwaves are an aspect of climate change that is only recently receiving increased scientific attention, especially for lower trophic levels and for high latitude regions. This project aimed at elucidating for the first time the response of Arctic phytoplankton to marine heatwaves through a series of experiments on differently complex phytoplankton assemblages, as well as their capacity and mechanisms of adaptation to such rapidly fluctuating temperatures. This was combined with extensive observations of natural Arctic spring blooms, and method development for population genetic analysis in natural contexts, in order to learn more about intraspecific selective processes, which are the basis for evolutionary adaptation. My results suggest that physiological and well as adaptive responses to marine heatwaves are not simply a time-limited version of responses to increased temperatures, and are therefore also not easily predictable based on our knowledge on stable temperature responses. On all levels of complexity, from single strain to natural community, I observed that not only warm phases, but also the cold-phases following a heatwave were influential moments for the performance and composition of primary producers, and often appeared more detrimental than the warm phase itself. This importance of cold-phases was surprising, and complicates the mechanistic understanding of heatwave responses, but is especially important since few studies so far have been investigating this aspect of temperature fluctuation. I hope therefore that the publications from this project will act as an incentive for future research in this field. Through the continuation of a time-series on Arctic diatom population dynamics, I also produced a unique record of intraspecific bloom properties which we will publish soon. Most prominently, it shows that populations of the same diatom species differ in composition between years, but are remarkably well connected between years through bentho-pelagic coupling with resting stages from the sediment. In order to improve the intraspecific resolution of such studies, I am still in the process of extending the microsatellite-based method currently used to a more elaborate approach based on single-nucleotide polymorphisms (SNPs), which should be finished throughout the year and could greatly increase the informativeness of such datasets.

Publications

• Annual congress of the German Limnological Society (DGL),September 2022, Konstanz, Germany, Oral presentation: Resilience and adaptive mechanisms of Arctic phytoplankton populations under marine heatwaves
  Wolf, K.K.E., Hoppe; C.J.M., Leese, F., Rost, B., John, U. & Schaum E.
  
• Invited talk at the annual meeting of the Research Training Group at the University of Konstanz, Germany (18.10.22) Adaptive mechanisms of phytoplankton in a changing Arctic: plasticity, intraspecific dynamics and community resilience
  Klara Wolf
  
• nternational Conference on Polar and Alpine Microbiology, October 2022, Potsdam, Germany, Poster: Adaptive mechanisms of phytoplankton in a changing Arctic: Acclimation, microevolution and ecological shifts under heatwaves
  Wolf, K.K.E., Hoppe; C.J.M., Schaum, E., John, U. & Rost, B.
  
• ALPOLE Seminar, EPFL Valais, Switzerland (26.6.23) Arctic phytoplankton blooms and adaptive mechanisms in a changing world
  Klara Wolf
  
• ASLO Aquatic Sciences Meeting, June 2023, Mallorca, Spain, Poster: Resilience and adaptive mechanisms of Arctic phytoplankton under heatwaves: Acclimation, microevolution and community resilience
  Wolf, K.K.E., Hoppe; C.J.M., Rost, B., John, U. & Schaum, E.
  
• European Phycological Congress 8 in Brest, France (22.8.23): The hidden flows within species: Phytoplankton population dynamics in Arctic assemblages
  Klara Wolf
  
• Seasonal plankton dynamics in Kongsfjorden during two years of contrasting environmental conditions. Progress in Oceanography, 213, 102996.
  Assmy, Philipp; Cecilie, Kvernvik Ane; Hop, Haakon; Hoppe, Clara J.M.; Chierici, Melissa; David, T. Divya; Duarte, Pedro; Fransson, Agneta; García, Laura M.; Patuła, Weronika; Kwaśniewski, Sławomir; Maturilli, Marion; Pavlova, Olga; Tatarek, Agnieszka; Wiktor, Jozef M.; Wold, Anette; Wolf, Klara K.E. & Bailey, Allison
  
• Winners and Losers of Atlantification: The Degree of Ocean Warming Affects the Structure of Arctic Microbial Communities. Genes, 14(3), 623.
  Ahme, Antonia; Von Jackowski, Anabel; McPherson, Rebecca A.; Wolf, Klara K. E.; Hoppmann, Mario; Neuhaus, Stefan & John, Uwe
  
• Heatwave responses of Arctic phytoplankton communities are driven by combined impacts of warming and cooling. Science Advances, 10(20).
  Wolf, Klara K. E.; Hoppe, Clara J. M.; Rehder, Linda; Schaum, Elisa; John, Uwe & Rost, Björn
  
• Multiannual patterns of genetic structure and mating type ratios highlight the complex bloom dynamics of a marine planktonic diatom. Scientific Reports, 14(1).
  Ruggiero, Maria Valeria; Buffoli, Marina; Wolf, Klara K. E.; D.’Alelio, Domenico; Di Tuccio, Viviana; Lombardi, Ernestina; Manfellotto, Francesco; Vitale, Laura; Margiotta, Francesca; Sarno, Diana; John, Uwe; Ferrante, Maria Immacolata & Montresor, Marina