Regional variation in Swedish acid sulfate soil microbial communities is influenced by temperature and geochemistry

Abstract

AbstractAcid sulfate soils are frequently described as the nastiest soils on Earth, and they pose environmental risks associated with their strong acidity and consequential mobilization of toxic metals present in the soils. Within Sweden, acid sulfate soils have been extensively studied around the northern Baltic coastline and have now been found to occur throughout the area below the maximum Holocene marine limit that stretches for some 2000 km from North to South. This study investigated 20 active acid sulfate soils (field tested pH < 4.0) collected throughout this area that were tested for microbial community composition using 16S rRNA gene amplicons, representing a novel study of microbial communities in ripening zones across a broad regional scale. The microbial community compositions exhibited a north (boreal zone) to south (hemiboreal zone) regional divide, primarily within the oxidized zone (pH < 4.0), to a lesser degree in the transition zone (steep pH gradient), while little differences were observed in the reduced zone (near‐neutral pH). For instance, a higher relative abundance of Ktedonobacteraceae was identified in the northern boreal and Gallionellaceae in the southern hemiboreal oxidized zones. In addition, microbial taxa associated with iron and sulphur oxidation and reduction were identified, such as Acidobacteriaceae, Gallionellaceae and Koribacteraceae that have been previously identified in other acid sulfate soils and acid mine drainage settings. The predominant controls of the microbial community differences were the north–south divide indicative of a strong soil‐temperature effect followed by soil zones suggesting an influence of the soils' pH and/or redox conditions.