Silver film response to sulfate reduction activity in alpine and subalpine wetlands, 2022.

Alpine ecosystems serve as crucial water resources for many areas of the world, and biogeochemical cycling in these regions can influence the chemistry of water flowing into downslope watersheds. Alpine and subalpine wetlands are understudied systems of particular interest since lowland wetlands are known to have high rates of biogeochemical activity that can disproportionally affect carbon (C) and nutrient uptake, sequestration, and transformations within the landscape. Wetland processes play a central role in sulfur (S) transformations and have conditions that can support sulfate reduction. Sulfate reduction determines the sequestration of S in wetlands and interacts closely with a multitude of other element cycles, including iron, carbon, nitrogen, and mercury. Previous work in Niwot alpine and subalpine wetlands noted large variability in sulfate reduction rates within wetland soils. Samples taken less than a meter away from each other sometimes showed almost 70x higher or lower rates (Rea, unpublished work). This work sought to adapt a silver film method to quantify sulfate reduction rates over small-scale spatial areas. The method proved valuable as a quick indicator of sulfate reduction activity and was able to visualize soil heterogeneity. However, the silver films were not sensitive enough to quantify sulfate reduction rates in situ.