Organic matter in Archean hydrothermal cherts may contain molecular traces of early life. Alteration processes during and after deposition, however, may have obliterated potential biosignatures. Our results from modern analog samples (Pleistocene cherts from Lake Magadi, Kenya) show that biomolecules can survive early hydrothermal destruction in the macromolecular fraction of the organic matter. A conservation of molecular biosignatures in Archean hydrothermal cherts therefore seems possible.

Sapropels are layers of sediment that regularly occur in the Mediterranean. They indicate periods when the Mediterranean Sea water contained no oxygen, a gas vital for most large organisms. This research investigated a key process in the nitrogen cycle (anaerobic ammonium oxidation, anammox), which removes nitrogen – an important nutrient to algae – from the water, during sapropel events. Using lipids to trace this process, we found that anammox was active during the no-oxygen times.

James Ross Island offers the opportunity to study the undisturbed interplay of microbial activity and pedogenesis. Soils from two sites representing coastal and inland conditions were chosen and analyzed with a wide range of techniques to describe soil properties. We are able to show that coastal conditions go along with more intense weathering and therefore favor soil formation and that microbial communities are initially more affected by weathering and structure than by chemical parameters.

Calcareous nannoplankton are photosynthetic plankton producing micrometric calcite platelets having a fossil record covering the past 200 Myr. Based on species richness, platelets size and abundance we observed four evolution phases through time: Jurassic–Early Cretaceous invasion phase of the open ocean, Early Cretaceous–K–Pg extinction specialization phase to the ecological niches, post-K–Pg mass extinction recovery and Eocene–Neogene establishment phase with domination of a few small species.

Regardless of the size and landscape context of surface water in frozen peatland in NE Europe, the bio- and photo-degradability of dissolved organic matter (DOM) over a 1-month incubation across a range of temperatures was below 10 %. We challenge the paradigm of dominance of photolysis and biodegradation in DOM processing in surface waters from frozen peatland, and we hypothesize peat pore-water DOM degradation and respiration of sediments to be the main drivers of CO₂ emission in this region.

Measuring ecosystem properties in the ocean is a hard business. Recent availability of data from Biogeochemical-Argo floats can help make this task easier. Numerical models can integrate these new data in a coherent picture and can be used to investigate the functioning of ecosystem processes. Our new approach merges experimental information and model capabilities to quantitatively demonstrate the importance of light and water vertical mixing for algae dynamics in the Mediterranean Sea.