Microbial biodiversity during the Messinian salinity crisis
The change in seawater chemistry established in the course of the MSC apparently caused the overall demise of eukaryotes and particularly metazoans (e.g., Bellanca et al., 2001). Such critical conditions for life were confirmed in the studied sections by the size decrease and the progressive disappearance of calcareous microfossils following the onset of the crisis. On the other hand, the BIOCLIMA data set revealed that other types of microorganisms were able to take advantage from the changing environment. For instance, ubiquitous filamentous fossils interpreted as remains of sulfide-oxidizing bacteria (Dela Pierre et al., 2014, 2015) were recognized in all studied lithologies (carbonate layers, organic-rich shales, gypsum), representing a common, but poorly constrained biological component of the MSC.
Apart from these filamentous bacteria, BIOCLIMA documented a diversification of archaeal molecular fossils at the onset of the MSC (Natalicchio et al., 2017). Archaeal molecules typical of normal marine conditions were found in the sediment deposited before the crisis, in agreement with the present calcareous microfossils. Interestingly, these planktic marine archaea survive the advent of the crisis but, at the same time, new archaeal organisms typical of more extreme conditions (most likely high salinity or seawater with modified chemistry) appeared. Molecular fossils and in particular those sourced by archaea consequently serve to trace the environmental changes in the course of ancient environmental crises. |