Cold water coral reefs are known as biodiversity hotspots on continental margins. They are nutrient-rich and three-dimensionally very complex ecosystems, which may influence microbial diversity to a considerable extent. Many microbes occupy distinct niches on animal surfaces, tissues and exudates, forming symbiotic, commensalistic or pathogenic relationships with their hosts. It is not known to which extent microbial assemblages are specific for different coral surfaces. Hence, the aim of our work is to explore in which ways cold-water coral reefs provide specific microbial habitats and niches.

Using a combination of high-resolution molecular techniques and multivariate statistics, we investigate microbial community structures and dynamics of different reef-associated habitats such as coral skeleton, tissue, and mucus as well as ambient seawater and proximal sediment. Special focus is thereby given to the question in how far cold-water corals act as “ecosystem engineers” for microbial communities by shaping their diversity via habitat differentiation or organic matter release.

Main achievements include:

• a multi-scale study on bacterial diversity and dynamics occurring with the two  main reef-building corals, Lophelia pertusa and Madrepora oculata, along horizontal and vertical gradients within one well-studied, proliferating reef ecosystem, as well as among reefs of different location and geomorphology.
• a comparative analysis of bacterial communities hosted by distinct microbial habitats associated with the cold-water coral Lophelia pertusa from in situ (fjord) and laboratory (aquarium) environments.
• laboratory incubations investigating the effects on microbial diversity and activity triggered by the release of cold-water coral organic matter (mucus) into the reef water column.
• an initiation of a cross-ecosystem comparison of bacterial community diversity in cold- and warm-water corals reefs.

Contact: A. Ramette, S. Schöttner

Literature:

Schöttner, S., Hoffmann, F., Wild, C., Rapp, H.T., Boetius, A. & A. Ramette (2009). Inter- and intra-habitat bacterial diversity associated with cold water corals. ISME Journal 3: 765-769.

Wild, C., Mayr, C., Wehrmann, L.M., Schöttner, S., Naumann, M., Hoffmann, F. & H.T. Rapp (2008). Organic matter release by cold water corals and its implication for fauna-microbe interaction. Marine Ecology Progress Series 372: 67-75.

Roberts, J.M., Wheeler, A.J. & A. Freiwald (2006). Reefs of the Deep: The biology and geology of cold-water coral ecosystems. Science 284: 118-120.