Coordinator: Prof. Dr. Martin Wahl, Dr. Frank Melzner, Dr. Catriona Clemmesen-Bockelmann

Mission:

An urgent challenge for understanding the functioning and fate of ecosystems in times of global change is to upscale our investigations in concept, time and space. Thus, we strive to move from investigating single species to entire communities, from single ontogenetic stage to multi-generation studies, and from single-site studies to global comparisons.  

Past research on the biological effects of climate or global change often lacked generality because the responses measured were specific to the chosen variable, species, developmental stage, time of year or geographic region. While particular data were often robust and reliable, they did not allow any general conclusion on community and ecosystem level processes. In the meantime we have learned that the sensitivity to stress differs among stages and species that multiple stressors may interact and that populations and communities may adapt to stressors through evolutionary changes.

Our integrative approach will comprise the study of single species and communities in a multi stressor environment, considering all ontogenetic life stages, trans - generation effects and present and predicted natural fluctuations of environmental variables. The objective is to investigate the mechanistic basis of amplifying and buffering interactions among stressors, biotic interactions and developmental phases, including an evolutionary ecophysiological approach. In addition, we will study selected questions with global replication of study sites and environments. 

Scientific Questions include:

1. How does stress sensitivity differ among physiological processes, ontogenetic stages, among different populations and species, and as a response to different stress scenarios? 
2. How rapidly can populations and species adapt evolutionarily to an altered environmental regime, what are the mechanisms that enable adaptation and what are possible trade-offs? [link with Topic 3-WP1]
3. How can single species assessments of physiological and evolutionary stress responses be up-scaled to the community and ecosystem level? [cooperation with Topic 2, link with Topic 3-WP1]

Contents and Goals

In the coming years, we will conduct up-scaled investigations on the ecological and evolutionary responses to stress and climate change. The up-scaling will be realized at several levels: in space (from the aquarium to the mesocosm to field experiments on the regional and global scale), time (from single to multiple generations), ecologically (from the species to the community level), conceptually by integrating multiple responses (physiological, evolutionary, ecological) and by moving from single stressor treatments to the simulation of predicted scenarios. 

Research Highlight 1: Evolutionary adaptation: In order to assess the capacity for rapid adaptation to stressor regimes expected in the future, we will carry out selection experiments over multiple generations (2-1000 generations) using uni- and multicellular model organisms of ecological importance. Recent evidence suggests significant adaptation capacity of calcifying unicellular algae (coccolithophorids) with a rapid generation turnover (days), when exposed to simulated ocean acidification over 500 generations. Even in long-lived species such as fish, rapid adaptation to future ocean conditions is possible over few generations given long-standing genetic variation. Hence, in order not to overestimate the negative impacts of future climate change on species and communities, we will make an effort to work on fewer model organisms that we will study more closely and for longer time periods under tightly controlled laboratory conditions. We plan on establishing multi-generation cultures of keystone marine species (e.g. the blue mussel Mytilus edulis and its main predator, the sea star Asterias rubens; the coccolithophorid Emiliania huxleyi) that will be conducted in the state-of-the-art laboratory and cold room facilities available at GEOMAR and CAU Kiel (Kiel Marine Organism Culture Centre, KIMOCC). We will investigate phenotypic and genotypic variability of adapted cultures and use genetic, biochemical and advanced imaging techniques, as well as ecophysiological assays to understand in detail the mechanisms that promote adaptation to stress matrices expected in the future. Within-generation experiments on mass-spawning, commercially-important fish species will address the sensitivity and standing genetic variation for stress tolerance. A second line of research will focus on comparing populations of the same species with a different background in terms of habitat variability using classical breeding designs to estimate phenotypic versus genotypic variability of cultures exposed to stress matrices projected into the future. If appropriate, state-of-the-art transcriptomic and genomic technologies will be applied to characterize gene variants that confer increased fitness upon adaptation. Some of the above projects in particular the acclamatory and adaptation responses to ocean acidification, will be conducted in cooperation with the AWI within the BIOACID project, partly in joint experiments. The overarching goal is to address how much evolutionary adaptation will contribute to the maintenance of community structure, and ecosystem functioning. 

Research Highlight 2: Up-scaling to community level: Large outdoor mesocosm facilities (“Kiel Benthocosms”) and pelagic mesocosms in climate chambers will allow us to simulate predicted natural stress regimes and study their impact on communities and ecosystem services. In microbial, planktonic and benthic systems we will apply multiple stresses, either acting simultaneously or sequentially and investigate the phenotypic and genotypic responses of populations and communities, allow for taxonomic and functional re-structuring of the communities and investigate the consequences for ecosystem services. We are particularly interested to find out when stress leads to hardening or sensitizing of populations with regard to the same and different stress. Also relevant are studies on the distribution of sensitivities or resistances to particular stressors among species (cross-tolerances, stress hyperspace). Care will be taken to choose the identity, intensity, combination and duration of stresses and stress regimes according to existing spatial gradients and plausible predictions. These experiments should be long enough to allow for responsive changes in genetic population structure (adaptive evolution) or taxonomic community composition. Experiments will also integrate the aspects of natural fluctuations and seasonality. In the benthocosms, the “control” regime will exactly mimic today’s conditions including daily to monthly fluctuations whereas the “future” regime consists of one or several delta treatments, where predicted shifts in temperature, pCO2 or other variables are dynamically added to “today’s” values. The response of species and communities will be examined in different seasons, since both the stress intensity and the stress sensitivity vary seasonally. More specific experiments will focus on the role of environmental change for host-epibiont, host-parasite and host-symbiont interactions, including microbes and viruses. The core question is whether hosts or epibionts/parasites/pathogens indirectly benefit from global change induced stress. In a first phase, we will examine how climate change (warming x acidification x desalination) will lead to a restructuring of communities at the genetic and/or phylogenetic level, and how the “new” communities differ with regard to ecosystem services and sensitivity to more regional stress (eutrophication, anoxia, heat wave). In a second phase, we plan to compare these community responses among regions with different stress histories.

Research Highlight 3: Experimentation goes global: Once we have achieved expertise at the local scale, we plan to initiate large modular experiments to compare the effects of global change on community structure, diversity and ecosystem services at the regional and global scale. Small, modular experiments at the global scale (5-6 biogeographic regions) have been and will be run as pilot studies assessing the robustness of climate change responses (see GAME project coordinated by GEOMAR). More in-depth investigations will be run comparatively among regions. Here, we preferentially compare responses to environmental stress among fluctuating and stable systems (e.g. Baltic versus North Sea or Mediterranean) and among regions in a large-scale environmental gradient (e.g. from the outer to the inner Baltic following the decreasing salinity gradient).

The combination of small in-depth investigations and more holistic investigations incorporating several factors, several response levels and several regions will provide a sound understanding of the processes, consequences and risks of natural stress in general and climate change in particular.