Seasonally, snow covers up to 45 million square km and snow melt provides important water and nutrient resources to ecosystems and human populations. Recent studies have documented active microbial communities in glacial and arctic snow and ice that contribute significantly to carbon (C) and nitrogen (N) cycling. In seasonal snow, a range of microbial taxa have also been discovered, but their contribution to carbon and nitrogen cycling across different environments is largely unexplored. The purpose of this study was to understand how seasonal snow microbes might contribute to C and N cycling across a gradient of subalpine landscape types throughout the snow melt period. We collected seasonal snow from March to June 2019 at forest and meadow sites at three elevations in the Snowy Range, WY. For each snow sample we measured environmental variables including concentrations of dissolved organic carbon (DOC), nitrate (NO3-), nitrite (NO2-), phosphate (PO43-), sulfate (SO42-), ammonium (NH4+), calcium (Ca2+), and potassium (K+). We also conducted extracellular enzyme assays to measure potential activity of seven enzymes (leucine aminopeptidase (LAP), N-acetyl-beta-glucosaminidase (NAG), alpha-glucosidase (AG), beta-glucosidase (BG), cellobiohydrolase (CBH), beta-xylosidase (BX), and phosphatase (PHOS) to better understand the potential role of snow microbes in biogeochemical cycling in seasonal snow.
Results/Conclusions
From March to June, DOC increased across the sampling dates from 0.63±0.19 to 3.19±1.85 mg L-1 in forest sites and 0.47±0.07 to 1.08±0.31 mg L-1 in meadow sites. Snow NH4+ and NO3- concentrations were relatively constant across sampling dates, averaging 0.23±0.16 mg L-1 and 0.24±0.16 mg L-1, respectively. Generally, enzyme activity was higher in forest samples than in meadow samples. Enzyme activity was typically low during the sampling dates in March and April and increased in May and June. Ordination analyses showed that enzyme activity in the forest samples was influenced by DOC, NH4+, NO3- , Ca2+, and SO42- (p <0.05), while enzyme activity in meadow samples was influenced by DOC, NH4+, NO3- , K+, and SO42- (p <0.05). This study demonstrates that microbes in seasonal snow can transform atmospheric inputs and that these processes are likely of larger magnitude in warmer environments and in environments with more organic substrates. Future research should aim to better understand drivers and rates of microbial biogeochemical processes in snow because changes to seasonal snow duration and timing could affect nutrient processing and inputs to terrestrial and aquatic ecosystems across large areas.