Remote characterization of Antarctic microbial mat communities

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Virginia Tech

The McMurdo Dry Valleys, Antarctica are ecosystems where life approaches its environmental limits. Cyanobacteria, however, have adapted to survive in this extreme environment as the most dominant life form and the main drivers of primary productivity (i.e., photosynthesis). Cyanobacterial communities exist on soil surfaces adjacent to glacial meltwater streams layered in mats up to several cm thick. The cryptic nature of these communities and their patchy distribution 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, where we surveyed and sampled seven 100 m2 plots of microbial mats for percent ground cover, ash-free dry mass, and pigment content. Multispectral analyses revealed spectral signatures consistent with photosynthetic activity (relatively strong reflection at near-infrared wavelengths and relatively strong absorption at visible wavelengths), with average NDVI values of 0.09 to 0.28. Strong correlations of microbial mat ground cover (R2 = 0.84), biomass (R2 = 0.74), chlorophyll-a content (R2 = 0.65), and scytonemin content (R2 = 0.98) with logit transformed NDVI values demonstrate that satellite imagery can detect both the presence of microbial mats and their key biological properties. Using the NDVI – biomass correlation we developed, we estimate carbon (C) stocks of 21,715 kg (14.7 g C m-2) in the Canada Glacier Antarctic Specially Protected Area. By quantitatively comparing biological surface observations to NDVI, this is the first satellite-derived estimate of microbial mat biomass for this region of Antarctica.