Coordinators: Prof. Dr. Ulrich Sommer, Prof. Dr. Johannes F. Imhoff, Dr. Birte Matthiessen 

Mission:

Biodiversity research at GEOMAR has a triple goal: exploring hitherto unknown marine biodiversity including chemical diversity of bioactive substances, understanding the cause of biodiversity change and prediction the risks for ecosystem functioning.  

The extent of ocean biodiversity is even less described than its terrestrial counterpart. At the same time, biodiversity worldwide is unprecedentedly declining with severe negative consequences for oceans’ ecosystem functions, such as sequestration of carbon and nutrients, build-up of biomass and 3-dimensional habitat structure (e.g. reefs and macroalgal beds), the recreational value of the sea and the provision of marine biological resources, including chemical natural products with application potential. The loss of biodiversity affects all levels of organization, from genetic impoverishment of species to species loss to the loss of entire functional groups such as top predators and ecosystem engineers. The ongoing diversity loss will thus potentially impair ecosystem functioning and the resilience to external pressures. On the global scale, changes in biodiversity results from the balance between speciation and extinction and on the local scale from the balance between immigration and exclusion shaped by biotic interactions and physico-chemical conditions.

Scientific Questions: 

• What is the unknown biodiversity we can find and characterize in less well-known and extreme habitats, such as cold and hot deep-sea vents, microbial mats and hypersaline brines?
• Is chemical diversity of produced bioactive substances related to the biological diversity of producing microorganisms?
• What causes species and genetic diversity change and what is the risk of genetic impoverishment for the survival of species?
• What are the consequences of biodiversity loss for the functioning and the resilience of ocean ecosystems and how does biodiversity loss compare and interact with current environmental change?

Contents and Goals

Discovery of unknown biodiversity requires increased efforts to access remote ecosystems and ecosystems inaccessible by conventional sampling tools. The biodiversity of functional genetic groups of macro- and microorganisms will be analysed in selected marine habitats, with increased efforts in the deep sea, since we have access to the necessary tools (e.g. ROV that can dive to depths of up to 6000 m). In addition to classical methods, genomic and metagenomic approaches will be applied, analysing the biodiversity of functional genetic groups in selected habitats.

Research Highlight 1: Biodiversity discovery, application and conservation: Exploratory biodiversity research is focussed on highly selected specific topics, e.g, marine microbial biodiversity, which still belongs to the most understudied components of global biodiversity, such as deep sea microbial (bacteria and fungi) diversity, including those involved in symbiotic and parasitic interactions with macroorganisms, Symbiotic and parasitic interactions involve a multitude of signalling and defence mechanisms involving small bioactive compounds, which still need to be explored and offer application potential for drug development, crop protection and cosmetics. 

In addition to classical methods, we envisage an increasing application of genomic and metagenomic approaches, analysing the biodiversity of functional genetic groups in selected habitats. Increased efforts will be invested into whole genome sequencing of microbes, including bacteria, microalgae, pathogens and symbionts. Genes involved in specific biosynthetic pathways of secondary metabolite biosynthesis will be characterized and used as tools to identify producer strains. At the same time, such knowledge may shed light on community functioning via chemical communication and interaction. Conservation-oriented research puts its emphases on large, slow growing animals at high trophic levels  (“charismatic meagafauna”), because these organisms suffer from the highest extinction risks. Examples are sea turtles, anadromous salmonids and the European eel.

Research Highlight 2: Causal biodiversity research: The causal and functional biodiversity research will mainly focus on experimentation complemented with field research along natural diversity gradients.  Experimental approaches will range from populations/communities artificially assembled from cultures with known genotypic composition to more realistic and less controlled approaches using natural communities subject to different regimes of stress and disturbance. In accordance with increasing awareness of genetic diversity, classical experimentation at the level of functional group and species diversity will therefore be augmented by manipulations and assessments of neutral and functional genetic diversity. To this end, functional genetic diversity will be assessed and then manipulated based on state-of-the-art genomic technologies, for example global transcription profiling and genome scans. Because of their short generation time and ease of experimental handling, but also because of its outstanding role in global ocean biogeochemistry, plankton will serve as the model system in most cases. 

Causal biodiversity research will focus on the empirical test of the recently emerged “neutral theory of biodiversity.” While all coexistence mechanisms studied so far rely on differences between species in their environmental requirements and abilities (concept of the “ecological niche”), the neutral theory claims (almost) infinite coexistence of species because of the absence (smallness) of competitive traits (“neutral theory of biodiversity”). A recent modification assumes niche differentiation between clusters of species and neutrality within clusters. The neutral theory has the additional appeal that it is analogous to the neutral theory of population genetics, i.e. the dynamics of genetic diversity in the absence of selection, which would allow for across-scale synthesis of marine ecological concepts. While this theory has been tested by numerical simulation models, it still remains to be tested empirically in marine ecology. From today’s perspective, the empirical test of the neutral theory forms the last frontier of ecological competition-coexistence research. While it is practically impossible to retrieve all ecophysiological parameters needed to assess neutrality for a sufficient number of species, it is possible to use interspecific difference and similarity in the responses to multiple experimental perturbations as a proxy for niche differentiation vs. neutrality. The mesocosms facility in the culture rooms and the benthocosm system of GEOMAR forms an excellent infrastructural base for perturbation experiments of this kind. 

Research Highlight 3: Ocean biodiversity – ecosystem functioning: The analysis of the functional role of biodiversity, i.e. its contribution to ecosystem processes and stability has mostly been restricted to experimental communities artificially assembled from clonal cultures. These represent only the lower end of the natural diversity gradient and do not mimic natural scenarios of biodiversity loss, where extinction is not random but falls preferentially on rare species and those that are particularly sensitive to environmental stressors. In order to significantly progress beyond the current state-of-the-art in experimental biodiversity-ecosystem function research, we will perform biodiversity-function studies using natural, taxonomically and genetically rich primary producer communities subject to realistic species loss or genetic impoverishment scenarios. We aim to quantify and compare the contributions of biodiversity loss and direct effects of external drivers (environmental pressures) on ecosystem functions. In order to achieve this goal, diversity loss scenarios and environmental stress (e.g. increased temperature, ocean acidification and deoxygenation) will be combined in pelagic and benthic mesocosm experiments with natural plankton and benthos communities in different regions of the world. This approach allows us 1) to understand how rapidly changing environmental conditions independently affect diversity loss and ecosystem functioning [link to joint experiments with Topic 3-WP2, Highlight 2], and 2) to quantify how the effect of diversity loss compares and adds up to direct drivers on key processes (nutrient up-take, productivity) affecting ecosystem functions such as inorganic and organic carbon (i.e. biomass) accumulation and food quality. Both components are of major importance for incorporating realistic and quantifiable effects of biodiversity loss on the transfer of photosynthetically fixed carbon into the ocean food web and the functioning of the biological carbon pump/global carbon and nutrient cycles [link with Topic 2].