Scientific research has many faces. For an international research team from Germany, Austria and Switzerland, it is a journey into both the depths of Lake Constance and the distant past: What was life like in and around Lake Constance during and since the last ice age? Which biological communities can be identified on the basis of the genetic material found in the sedimentary deposits of the lake bed? What do these residues reveal about the effects of past climate change on local species and populations? And which microorganism communities are still active in these old sediment layers?
 
Two biologists from the University of Konstanz, Professor Laura Epp from the Limnological Institute and Dr David Schleheck (Privatdozent) from the Department of Biology are working on finding answers to these questions as part of an international research project involving geologists and geochemists led by Professor Antje Schwalb from the Institute of Geosystems and Bioindication at the Technische Universität Braunschweig. The aim of the project is to develop a historical overview of the Lake Constance region’s climate and environment as well as their effects on the lake ecosystem. In order to recover core samples from the lake bed and then carry out geological, geochemical and biological analyses of their contents, the researchers are utilizing the state-of-the-art and specially developed HIPERCORIG drilling platform in combination with the sampling system “Direct Push”, which can penetrate up to 100 metres deep into the sediment of the lake floor at a water depth of 200 metres.

The proposal for “HIPERCORIG” was submitted jointly by the Technische Universität Braunschweig and the Bochum University of Applied Sciences with the support of the Deutsche Forschungsbohrkonsortium (GESEP) e.V. and funded via the priority programme SPP 1006 – International Continental Drilling Program (ICDP) by the German Research Foundation (DFG) with EUR 1.1 million between 2016 and 2018. The system was built by the Austrian company UWITEC, which specializes in the design and development of such drilling technology. Further project partners include the Institut für Seenforschung der Landesanstalt für Umwelt Baden-Württemberg, the Helmholtz Centre Potsdam - German Research Centre for Geosciences, the Leibniz Institute for Applied Geophysics in Hanover, the Leibniz Institute for Baltic Sea Research Warnemünde and the University of Bern in Switzerland.

Due to its small size, the platform can be transported in a few containers and set up without cranes. Once it completes its work on Lake Constance, it can be used for other national and international research projects in remote and difficult to access areas around the world. After experiencing some weather-related delays, the researchers are planning to complete their sampling work by 15 July. Find out more about the work carried out on the drilling platform on the blog of the TU Braunschweig.

Once the work on Lake Constance is completed, the researchers can then begin with the actual scientific work. The sediment cores will be stored and studied at the University of Bern, where researchers will focus on palaeoclimatological topics. In order to find out more about the climatic conditions in the past, it is necessary, among other things, to identify and measure the amount of planktonic remains in the various sediment layers.
 
Before the cores are transferred to Switzerland, however, several researchers from the University of Konstanz’s Department of Biology will examine them for remains of ancient DNA and active microorganisms. In order to prevent potential contamination of the sediment, Laura Epp, David Schleheck and doctoral student Anan Ibrahim will take take great care to remove small samples from the approximately two-metre-long cores in a specially equipped cold storage room at the university. They hope that their paleolimnological and microbiological investigations will provide answers to questions that have so far eluded them, due in part to insufficient technical capabilities.
 

To be able to identify both the organisms that are still living in the deep sediment layers of Lake Constance and the metabolic processes that have enabled them to survive, the researchers need to ensure that the bacterial communities are not affected by the transport. To this end, they need to maintain a constant temperature of four degrees Celsius for the cores as they are moved to the laboratory. Furthermore, the organisms need to be moved under the anoxic conditions they are used to in their natural habitat: “Oxygen is actually toxic for most of these life forms,” says Schleheck.
 
There are already indications that organisms such as Atribacteria or so-called Hadesarchaea are specialized to live in this deep biosphere. “Nutrients have become very scarce at those depths. With a relatively high metabolic expenditure, these organisms are able to produce and maintain enough energy to survive by taking advantage of special respiration and fermentation processes as well as metabolic coupling mechanisms,” explains Schleheck.
 
And the organisms grow very, very slowly, if at all: “Life is an extremely slow process for them. While a bacterium such as Escherichia coli can double its population approximately every 20 minutes under optimal conditions in a laboratory, microorganisms in deep sediment layers require months, years or even decades to double their populations – if they aren’t in a dormant state or 'deep sleep'. Even if we are able to simulate their growth conditions in the laboratory, it might take a long time before the microorganism populations grow into large enough groups for us to carry out a normal physiological-biochemical analysis on them.”