Understanding changes in biocrust communities following phosphate mining in the Negev Desert

Abstract

Biocrusts are key ecosystem engineers that are being destroyed due to anthropogenic disturbances such as trampling, agriculture and mining. In hyper-arid regions of the Negev Desert, phosphate has been mined for over six decades, altering the natural landscape over large spatial scales. In recent years, restoration-oriented practices were mandated in mining sites, however, the impact of such practices on the ecosystem, particularly the biocrust layer, has not been tested. Here, we evaluated post-mining biocrust bacterial communities and compared them to undisturbed (reference) biocrusts. We collected samples from four mining sites (each restored at a different year) and their corresponding reference sites. We hypothesized that post-mining bacterial communities would differ significantly from reference communities, given the slow regeneration of the biocrust. We also hypothesized that bacterial communities would vary among post-mining plots based on their restoration age. To test these hypotheses, we assessed the abundance and diversity of bacterial communities by sequencing the 16S rDNA and their photosynthetic potential by quantifying the abundance of cyanobacteria and chlorophyll a. The bacterial diversity was lower, and community composition differed significantly between post-mining and reference biocrusts. In addition, cyanobacteria abundances and chlorophyll a content were lower in post-mining biocrusts, indicating lower photosynthetic potential. However, no significant changes in bacterial communities were detected, regardless of the restoration age. We suggest that the practices implemented in the Negev mines may not support the recovery of the biocrust bacterial communities, particularly the cyanobacteria. Thus, active restoration measures are needed to accelerate the regeneration time of biocrusts at the hyper-arid Negev mines.