Lake Towuti is a deep tectonic basin surrounded by ophiolitic rocks and lateritic soils. Its geographic position in central Indonesia and relatively great age (estimated >500 ky) makes the lake a prime location to record paleoclimatic changes in the tropical Western Pacific warm pool in its sedimentary sequence. It was therefore chosen as a drilling target by the International Continental Scientific Drilling Program (ICDP). Ultramafic rocks and lateritic soils eroded from the catchment supply Lake Towuti with little sulfate but considerable amounts of iron oxyhydroxides/oxides, which trap the available phosphate, leading to extreme phosphate limitation and thereby restraining primary productivity.
Due to its great depth of ca. 200 m, Lake Towuti is stratified, with bottom water anoxia below ca. 130 m water depth. Anoxic bottom water allows for microbially mediated iron reduction and liberation of phosphorus. The extreme scarcity of sulfate and nitrate/nitrite in Lake Towuti’s anoxic bottom water represents conditions analogous to those of the Archean Ocean. Nevertheless, Lake Towuti mixes at least occasionally, resulting in transient oxygenation of its bottom water, which could profoundly change paleoclimatic and microbiological proxies. These peculiar settings along with the development of specific microbial metabolisms during early diagenesis make Lake Towuti an ideal site to study the deep biosphere with concomittant mineral formation under ferruginous conditions, such as those observed in ancient iron formations.
During two pilot campaigns in autumn 2013 and 2014, several short cores were retrieved from a shallow, intermediate and deep site presenting oxic to anoxic conditions at the water/sediment interface. Sediment cores were sampled on site for different analyses (i.e. pore water, cell count, sulfate reduction rate, extra/intracellular DNA sequencing). This initial geomicrobiological work provided a first dataset linking the geochemistry and microbiology of Lake Towuti sediments under different bottom water oxygenation levels. In May to July 2015, the ICDP Towuti Drilling Project recovered a total >1000 m of sediment cores from three sites, including a 114 m long core dedicated to geomicrobiological studies with a contamination tracer. This was the first time in the history of ICDP that a dedicated core for destructive geomicrobiological and biocheochemical analyses was taken.
Dr. Aurèle Vuillemin
Prof. James M. Russell – Brown University, Rhode Island, USA
Prof. Sean A. Crowe – University of British Columbia, Vancouver, Canada
Prof. Satria Bijaksana - Institut Teknology Bandung, Indonesia
Prof. Martin Melles – University of Cologne, Germany
Prof. Daniel Ariztegui – University of Geneva, Switzerland
Dr. Hendrik Vogel – University of Bern, Switzerland
Dr. Cynthia Henny – LIPI Research Center for Limnology, Bogor, Indonesia
FAMAFED – DFG no. VU 94/1-1
SNSF no. P2GEP2_148621
Vuillemin A., Horn F., Alawi M., Henny C., Wagner D., Crowe S., and Kallmeyer J. 2017. Preservation and significance of extracellular DNA in ferruginous sediments from Lake Towuti, Indonesia. Front. Microbiol. 8, 1440. doi: 10.3389/fmicb.2017.01440
Russell J.M., Bijaksana S., Vogel H., Melles M., Kallmeyer J., Ariztegui D., et al. (2016). The Towuti Drilling Project: Paleoenvironments, biological evolution, and geomicrobiology of a tropical Pacific lake. Sci. Dri. 21, 29–40. doi:10.5194/sd-21-29-2016
Vuillemin A., Friese A., Alawi M., Henny C., Nomosatryo S., Wagner D., et al. (2016). Geomicrobiological features of ferruginous sediments from Lake Towuti, Indonesia. Front. Microbiol. 7, 1007, 1-16. doi: 10.3389/fmicb.2016.01007