The deep seafloor below 200 m water depth covers approximately 65% of the Earth’s surface and therefore presents the largest continuous ecosystem on Earth, but also one of the least understood. Bacterial communities play an essential role for carbon and nutrient cycling in deep-sea sediments, and are thus an important component not only of benthic deep-sea ecosystems, but also of the global carbon cycle. Nevertheless, bacterial diversity and its distribution in deep-sea sediments of the world’s oceans remain largely unknown. My studies aim at developing a better understanding of bacterial diversity patterns and ecosystem functioning at the deep seafloor.
I specifically investigate patterns of bacterial community structure in an environmental and spatial context. Recently, we could evidence distinct energy-diversity relationships for bacterial communities in Arctic deep-sea sediments (Bienhold et al., in press, The ISME Journal). I am currently expanding analyses to a set of globally distributed deep-sea surface sediments to understand which contextual parameters are important drivers for changes in bacterial communities at the global scale.
The molecular methods applied include: Automated ribosomal intergenic spacer analysis (ARISA) (Fisher & Triplett 1999, Appl Environ Microbiol 65:4630-4636) and 454 massively parallel tag sequencing (Sogin et al. 2006, Proc Natl Acad Sci USA 103:12115-12120).
Chemosynthetic ecosystems in the deep sea (e.g., hydrothermal vents and cold seeps) present oases of life in an otherwise largely oligotrophic environment. Large organic food falls such as whale carcasses, wood and kelp can lead to the development of chemosynthetic environments in the deep sea which may act as stepping stones in the evolution and distribution of chemoautotrophic communities. Considerable effort has been spent on the exploration of hydrothermal vent and cold seep ecosystems as well as whale falls, but the role of wood falls as localized boosts of organic material to the deep seafloor remains largely unstudied. In the framework of the ESF EUROCORES EuroDEEP Project “Colonization processes in chemosynthetic ecosystems – CHEMECO” and the MPG-CNRS GDRE „Diversity, establishment and function of organisms associated with marine wood falls – DIWOOD”, we carried out wood colonization experiments in the Eastern Mediterranean deep sea to investigate the succession of colonization and the establishment of biogeochemical gradients at deep-sea wood falls (Figure 1). The aim of this study is to contribute to a better understanding of the microbial ecology and biogeochemistry of wood fall ecosystems and their role as biological and biochemical hotspots in the deep sea.
Wood colonization experiment in the Eastern Mediterranean deep sea. Picture taken by ROV Quest 4000 (Marum, Bremen, Germany) shortly after deployment during the Bionil cruise in 2006 (RV Meteor M76/2b).
|2012||RV Polarstern, ARK 27-3, IceArc, Central Arctic|
|2009||RV Maria S. Merian, MSM 13-3, Eastern Mediterranean (wood colonization experiments)|
|2008||RV Meteor, M 76/3B, Congo fan (cold seeps)|
|2007||RV Pourquoi Pas?, MEDECO-2, Eastern Mediterranean (wood colonization experiments)|
|2007||RV Polarstern, ANT XXIII/9, Prydz Bay, Antarktic (Geophysics)|