McMurdo Dry Valley (Antarctica) Stream Microbial Mat targeted loci environmental. microbial mat metagenome

Microbial mats are abundant in many alpine and polar aquatic ecosystems. With warmer temperatures, new hydrologic pathways are developing in these regions and increasing dissolved nutrient fluxes. In the McMurdo Dry Valleys, thermokarsting has released both nutrients and sediment, and has the potential to influence mats in glacial meltwater streams. To test the role of nutrients on community structure, we created nutrient diffusing substrata (NDS) with agar enriched in N, P, N+P and controls, and deployed them into two Dry Valley streams. We found N amendments (N and N+P) to have greater chlorophyll-a concentrations, total algal biovolume, more fine filamentous cyanobacteria, and a higher proportion of live diatoms than other treatments. Furthermore, N treatments were substantially elevated in members of Bacteroidetes and the diatom, Fistulifera pelliculosa. On the other hand, species richness was almost double in P and N+P treatments, and diatoms, coccoid green algae, and Proteobacteria were more abundant in both streams. Collectively, these data suggest that nutrients have the potential to stimulate mat growth and alter community structure in glacial meltwater stream mats, and the recent erosion of permafrost and accelerated glacial melt will likely impact resident biota in polar lotic systems here and elsewhere.