Microbially induced mineral formation at wood falls and whale falls
25. April 2019
In the deep-sea, where light is unavailable as energy source, chemotrophy is the only possible mode of primary production. Here, chemotrophic bacteria and archaea oxidize chemical compounds, which are for example present at hydrothermal vents. However, only very few environments of the deep-sea are characterized by hydrothermalism. Furthermore, deep-sea sediments contain little organic matter. Upon a local supply of large amounts of organic matter, chemoheterotrophic organisms can thrive and may even form the base of lush chemosynthesis-based ecosystems in some low temperature environments. Among such sites are wood falls and whale falls. These settings represent important and widespread locations of chemosynthesis in the deep-sea. In some previous studies, sulfate-reducing bacteria have been recognized to be among the most abundant bacteria degrading whale carcasses and wood. It has been shown that sulfate-reducing bacteria play a crucial role in the degradation of organic matter of wood falls. It was demonstrated these bacteria produce a significant amount of hydrogen sulfide. However, apart from some pilot studies, the composition of microbial communities on wood and whale falls has received little attention so far.
The purpose of this project is to perform (1) detailed petrographic investigations, (2) oxygen and carbon stable isotope of carbonates and (3) lipid biomarkers composition of wood and whale fall deposits from the rock record. The ultimate aim is to determine which microorganisms were active on and in wood residues and whale bones and to what extent they were involved in the formation of secondary authigenic minerals. This research will (1) allow to unravel which different types of microorganisms benefit from wood and whale falls, (2) constrain the modes of mineral formation, and (3) test to which extent the authigenic minerals can be used as archives of chemosynthesis-based life in the deep-sea.