Fish-processing effluent discharges influenced physicochemical properties and prokaryotic community structure in arid soils from Patagonia

Abstract

Along the Patagonian coast, there are processing factories of marine products in land that produce fish-processing effluents. The aim of the present study was to assess the physicochemical properties and the prokaryotic community composition of soils receiving fish-processing effluent discharges (effluent site-ES), and to compare them with those of unaltered soils (control site-CS) in the arid Patagonian steppe. We analyzed soil prokaryotic communities (using amplicon-based sequencing of 16S rRNA genes), soil physicochemical properties and fish-processing effluent characteristics. Soil moisture, electrical conductivity (EC), total and inorganic C were significantly higher in ES than in CS (p < .05). Effluent discharges induced a decrease in the total number of operational taxonomic units (OTUs) and in the Shannon diversity index (p = .0009 and .01, respectively) of soil prokaryotic community. Proteobacteria, Actinobacteria and Acidobacteria were the dominant phyla in CS, while ES soil showed a more heterogeneous composition of phyla. Linear discriminant analysis (LDA) effect size (LEfSe) analysis showed that fish-processing effluent discharges promoted an enrichment of Firmicutes and Bacteroidetes, which are active contributors to organic matter mineralization, along with a decrease of oligotrophic phyla such as Acidobacteria, Chloroflexi, Armatimonadetes and Nitrospirae, commonly found in nutrient-poor arid soils. The concentrations of inorganic C and ammonium, the EC and the soil moisture explained 73% of the total variation within the community composition. Due to its salinity and nutrients, fish-processing effluents have potential mainly for native salt-tolerant plant irrigation, however the impacts of soil prokaryotic community shifts over plant growth remain to be determined.

Keywords: Industrial wastewater; Prokaryotic diversity; Salinity; Soil C; Soil nutrients; V4 region of 16S rRNA gene.