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or lower rates (Rea, unpublished work).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.