09 Jan 2023
09 Jan 2023
Status: this preprint is open for discussion.

Only a minority of bacteria grow after wetting in both natural and post-mining biocrusts in a hyperarid, phosphate mine

Talia Gabay1,2, Eva Petrova3, Osnat Gillor2, Yaron Ziv1, and Roey Angel3 Talia Gabay et al.
  • 1Department of Life Sciences, Ben Gurion University of the Negev, 8410501, Israel
  • 2Zuckerberg Institute for Water Research, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 8499000, Israel
  • 3Institute of Soil Biology and Biogeochemistry, Biology Centre CAS, Na Sádkách 7, 370 05 České Budějovice, Czech Republic

Abstract. Biological soil crusts (biocrusts) are key contributors to desert ecosystem functions; therefore, biocrust restoration following mechanical disturbance is imperative. In the Negev Desert hyperarid regions, phosphate mining has been practiced for over 60 years, destroying soil habitats, and fragmenting the landscape. To understand the effects of mining activity on soil health, we previously characterized the biocrust communities in four phosphate mining sites over spatial (post-mining and natural plots) and temporal (2–10 years since restoration) scales. We showed that bacterial abundance, richness, and diversity in natural plots were significantly higher than in post-mining plots, regardless of temporal scale. In this study, we selected one mining site and used DNA stable isotope probing (DNA-SIP) to identify which bacteria grow in post-mining and natural biocrusts. Since biocrust communities activate only after wetting, we incubated the biocrusts with H218O for 96 hours under ambient conditions. We then evaluated the physicochemical soil properties, chlorophyll a concentrations, activation, and functional potential of the biocrusts. The DNA-SIP assay revealed low bacterial activity in both plot types and no significant differences in the proliferated communities’ composition when comparing post-mining and natural biocrusts. We further found no significant differences in the microbial functional potential, photosynthetic rates, or soil properties. Our results suggest that growth of hyperarid biocrust bacteria after wetting is minimal. We hypothesize that due to the harsh climatic conditions, during wetting bacteria devote their meager resources to prepare for the coming drought, by focusing on damage repair, and organic compound synthesis and storage rather than on growth. These low growth rates contribute to the sluggish recovery of desert biocrusts following major disturbances such as mining. Therefore, our findings highlight the need for implementing active restoration practices following mining.

Talia Gabay et al.

Status: open (until 03 Mar 2023)

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Talia Gabay et al.


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Short summary
This paper evaluates bacterial growth in biocrusts after a large scale mining disturbance in a hyper-arid desert, using a stable isotope probing assay. We discovered that bacteria in our biocrust samples resumed photosynthetic activity, but did not grow following hydration. Our paper provides insights to the effects of a large scale disturbance on biocrusts and their response to hydration, with implication to biocrust restoration practices in Zin mines.