Marl Pedological Formation - a Habitat for Microbial Community.

Marl pedological formation – a habitat for microbial community

Oksana Koryachenko, Ruben Girsowicz, Yosef Steinberger

The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel

Gypsum crust is a significant pedagogic and geomorphologic feature known as marl, widely dispersed in regions with slopes and ridges in the northern Negev Desert. The typical marls are soft, earthy, of a white, grey, or brownish color, and composed mainly of Ca(CO₃). The wide marl crust areas are barren, with streamside, well developed, and without perennial vegetation cover. Although soil systems have been widely studied, very little information can be found on the marl soils and even less on the biological component of marl present in the Negev Desert in Israel. We noticed that, in some places, a green-brown crust compound from an algae settlement in a previously uninhabited area was visible on the surface of the marl. Because of a lack of knowledge, it was decided to evaluate the microbial-community inhabitants in a marl crust in an attempt to distinguish between marl with algae on its surface and bare marl crust without algae cover. The objective of this preliminary study was to investigate the microbial community and abiotic components of the upper layer (0-3 mm) and the lower layer (3-5 mm) of marl and marl-with-algae soil collected from the Negev Desert. The biotic parameters (CLPP, functional diversity, microbial biomass, CO₂ evolution, and the metabolic quotient) were obtained using a MicroResp unit. Plate-counting allowed us to estimate fungal and bacterial population size while we used nested PCR with specific primers and Ion Torrent sequencing to analyze the population's diversity composition. Our results indicated significant differences in the microbial biomass and the diversity of the microbial communities between the two layers and between marl and marl-algae. Abiotic components, such as pH and calcium carbonate percentage, were very similar for the two marl crusts. In order to get a better understanding of marl microbial-community composition and function, further investigation is needed.