Cyanobacterial mat communities are the main drivers of primary productivity in the McMurdo Dry Valleys, Antarctica. These microbial communities form laminar mats on desert pavement surfaces adjacent to and within glacial meltwater streams, ponds, and lakes. The cryptic nature of these communities, their patchy distribution, and their ability to survive desiccation make assessments of productivity challenging. We used satellite imagery coupled with in situ surveying, imaging, and sampling to systematically estimate microbial mat biomass in selected wetland regions in Taylor Valley, Antarctica. On January 19th, 2018, the WorldView-2 multispectral satellite acquired an image of our study areas, occurring within 10 days of when we surveyed and sampled seven 100 m2 plots with visually distinct microbial mats for percent ground cover, ash-free dry mass (AFDM), and pigment content (chlorophyll-a and scytonemin). The satellite imagery was georeferenced, atmospherically corrected, and processed using the normalized difference vegetation index (NDVI). We examined the relationships between multispectral satellite data (i.e., logit transformed NDVI) and survey data (i.e., percent cover scaled biomass and pigments) using simple regressions of means.
Results/Conclusions
The microbial mat communities were dominated by the cyanobacteria Nostoc, ranging from 30-70% coverage. The microbial mats contained organic matter content ranging from 6.53 to 399 mg g-1 AFDM. Chlorophyll-a content of mats ranged from 0.61 to 48.5 μg g-1. Scytonemin, a UV screening sheath pigment, had concentrations ranging from 4.07 to 1163 μg g-1. Multispectral analyses revealed strong absorption of visible light (~ 0.4 – 0.7 μm) and strong reflectance of near-infrared light (> 0.7 μm), consistent with photosynthetic materials, with average NDVI values of 0.09 to 0.28. Strong linear and logarithmic correlations of microbial mat ground cover (R2 = 0.84, p < 0.01), microbial mat biomass (R2 = 0.74, p = 0.013), chlorophyll-a content (R2 = 0.65, p = 0.028), and scytonemin content (R2 = 0.98, p < 0.0001) with logit transformed NDVI values demonstrate that multispectral satellite imagery can detect both the presence and key biological properties of microbial mats. Using the NDVI – biomass relationship, we estimate an organic C inventory of 21,715 kg (14.7 g C m-2) in the Canada Glacier Antarctic Specially Protected Area. This is the first satellite-derived estimate of microbial mat biomass for this region of Antarctica.