Research Themes

Despite significant progresses in molecular techniques to unravel microbial diversity, still little is known about the ecological factors that shape bacterial and archaeal communities at different spatial or temporal scales and along environmental gradients. Microbial biodiversity, i.e. species richness and community structure, is at the center of our group’s focus, as its changes may have dramatic consequences on global biogeochemical processes in the oceans. Reproducible high-throughput, high-resolution molecular methods are used to assess microbial biodiversity in its environmental context such as coastal sandy sediments, coral-associated surfaces, microbial mats, oligotrophic deep-sea sediments, or deep-sea sediments impacted by high hydrocarbon fluxes. Molecular techniques such as Terminal Restriction Fragment Length Polymorphism (T-RFLP), Automated Ribosomal Intergenic Spacer Analysis (ARISA) and Next Generation Sequencing (NGS) provide a thorough analysis of the source of community variation for large datasets, and when combined with contextual parameters, enable disentangling the respective effects of multiple factors acting on microbial community structure and functions. Ecological processes implicated in community assembly are thus investigated from local to global scales.

The ocean is affected by global change in multiple ways: Hypoxic conditions in aquatic ecosystems increase in number and duration and are accompanied by changes in biodiversity and ecosystem functions. In many aquatic ecosystems, warming, eutrophication, acidification, and deoxygenation co-occur. An increased resource exploitation of the ocean such as by littering, mining and mineral extraction, fisheries, introduction of alien invasive species shows a substantial impact even in the remote deep sea. It is obvious that any of these factors alone or in combination will alter ocean ecosystems, but it is not trivial to monitor consequent changes in ecosystem biodiversity or function (e.g. productivity, remineralization, bioturbation) due to missing baselines, and due to the technical and logistical challenges of long- term observation in the sea. Furthermore, the role of microbes in global change effects and feedback mechanisms are not known.

Main recent achievements and current tasks include:

Extreme environments are defined by one or more environmental characteristics at which life operates close to its known limits. Often the greatest challenges to life are extreme temporal fluctuations or short-term impacts, which select for highly adapted organisms and alter community structure and function. In this regard, the main focus of our studies is to identify and quantify biogeochemical processes and their link to microbial diversity at different types of ecosystems with one or more extreme characteristics: cold seeps (EU 7th FP HERMIONE; Excellence Cluster MARUM), acidic vents (EU 7th FP ECO2), hydrothermal vents (Excellence Cluster MARUM), wood and whale falls (ESF EuroCores CHEMECO and MPG-CNRS GDRE DIWOOD), as well polar habitats (e.g. microbial-life in sea ice). To improve our knowledge of the functioning of these ecosystems we combine studies on the dynamics of fluxes and biogeochemical processes with biodiversity studies.

The marine environment still hosts many unexplored ecosystems with unknown functions in biogeochemical cycles and global ocean biodiversity. Especially the deep-sea realm is largely unknown due to its inaccessibility because of high pressure, total darkness, low temperature as well as its remoteness and size. Over the last decade there has been a great achievement in developing and using various under water platform, like ROVs, AUVs, crawler and observatories, to advance the exploration and research of the deep sea. To fully understand the link between oceanic processes and the response of ecosystems and communities to environmental change, the need forin situ observationenabled by fixed point and mobile platforms equipped with sensors is critical. To investigate long-term variations at cold seeps a deep-sea observatory has been developed and deployed at the Håkon Mosby Mud Volcano (EU 6th FP ESONET). An array of instruments for the observation of oxygen depletion in suboxic and hypoxic aquatic environments (EU 7th FP HYPOX) was used in the Black Sea.
These projects are carried out in close collaboration with the microsensor group.