Swedish Hypersulfidic Soil Material Incubations Suggest Temperature Mainly Drives Regional Microbial Community Variation

Abstract

Acid sulfate soils impact surrounding ecosystems with pronounced environmental damage via leaching of strong acidity along with the concurrent mobilization of toxic metals present in the soils and, in consequence, they are often described as the nastiest soils on Earth. Within Sweden, acid sulfate soils are distributed mainly under the maximum Holocene marine limit that stretches the length of the country, some 2000 km north to south. Despite only minor geographical differences in the geochemical composition of the Swedish acid sulfate soils, their field oxidation zone microbial community compositions differ along a north–south regional divide. This study compared the 16S rRNA gene amplicon-based microbial community compositions of field oxidation zones (field tested pH < 4.0) with reduced zone samples (field tested pH > 6.5) collected from the same field sites throughout Sweden that had acidified (final pH < 4.0) after laboratory incubation at approximately 20°C. The previously identified regional differences observed in field oxidation zone microbial compositions were notably absent in the laboratory incubation samples. Instead, a commonly shared community was selected for with few statistically significant differences regardless of regional origin. For instance, the potential eurypsychrophilic Baltobacteraceae family was found in higher relative abundances in the northerly region of the field oxidation zone samples than the southern regions and was notably absent from the laboratory incubation samples. Furthermore, the microbial communities of the laboratory incubation samples were dominated by acidophilic autotrophic Acidithiobacillaceae and chemoheterotrophic Rhodanobacteraceae and Burkholderiaceae that have optimal growth temperatures (≥ 20°C) greater than what was experienced by the field oxidation zone samples when sampled (~2°C–9°C). These data suggested that in the absence of significant geochemical differences, temperature was the predominant driver of microbial community composition in Swedish acid sulfate soil materials.