Effects of the cessation of fish-processing effluent discharges on the soil microbiome associated with saltbush patches

Abstract

In the present scenario of global water scarcity, treated wastewater from some industries -such as the fishing industry- is an interesting resource to consider for irrigation purposes. In a previous study in a Patagonian steppe site dominated by the native halophile shrub Atriplex lampa, fish-processing effluent discharges induced soil salinization, changes in the soil prokaryotic community structure and a reduction of its diversity. In this study we aimed to test if a period without effluent discharges allowed the recovery of the microbial community in soils from this Patagonian steppe site, by analyzing the prokaryotic communities of A. lampa patches during the fish-processing effluent discharges and four years after cessation of such discharges (sites ES1 and ES2, respectively). Additionally, we aimed to test if the soil prokaryotic community of A. lampa patches either exposed to effluent discharges (ES2) or from a coastal dune site (Du) share a common core microbiome as a result of their same shrub cover and similar soil salinity. Regarding the comparison between ES1 and ES2, prokaryotic richness estimators (Chao1 and ACE) increased significantly in ES2. In addition, the cessation of effluent discharges induced a rise of Actinobacteria, and a recovery of some oligotrophic phyla, which had decreased during the effluent discharge period. Regarding the comparison between ES2 and Du, the core microbiome in soils associated with A. lampa patches consisted of just a few taxa. Moreover, Du site revealed a signature of dune-specific prokaryotes comprising halotolerant/halophilic microorganisms adapted to marine and intertidal environments, whilst no such signature was observed in ES2. Overall, our results contribute to unraveling the soil prokaryote diversity associated to A. lampa as well as to a better understanding of the microbiomes from saline environments, having valuable implications for a sustainable reuse of fishing industry wastewaters for irrigation.