Remote characterization of photosynthetic communities in the Fryxell basin of Taylor Valley, Antarctica

Abstract

We investigate the spatial distribution, spectral properties and temporal variability of primary producers (e.g. communities of microbial mats and mosses) throughout the Fryxell basin of Taylor Valley, Antarctica, using high-resolution multispectral remote-sensing data. Our results suggest that photosynthetic communities can be readily detected throughout the Fryxell basin based on their unique near-infrared spectral signatures. Observed intra- and inter-annual variability in spectral signatures are consistent with short-term variations in mat distribution, hydration and photosynthetic activity. Spectral unmixing is also implemented in order to estimate mat abundance, with the most densely vegetated regions observed from orbit correlating spatially with some of the most productive regions of the Fryxell basin. Our work establishes remote sensing as a valuable tool in the study of these ecological communities in the McMurdo Dry Valleys and demonstrates how future scientific investigations and the management of specially protected areas could benefit from these tools and techniques.

Evaluating Alternative Metacommunity Hypotheses for Diatoms in the McMurdo Dry Valleys Using Simulations and Remote Sensing Data

“…The simulations required three general components to run (Figure 1, MCSim inputs): (1) a landscape map, (2) an initial metacommunity, and (3) parameters that determine the dispersal and recruitment dynamics that occur with each time step of the simulation. We used remotely sensed imagery from the WorldView-2 satellite (Figure 2) (Salvatore et al, 2020) and data from the MCM LTER monitoring record (Figure 3 and Supplementary Data Sheet 1) to create a simulation map ( Figure 4A and Supplementary Data Sheet 2) and an initial contrived diatom metacommunity (Supplementary Data Sheet 3) as a common starting point for all simulation scenarios. We created 10,000 independent simulations to explore how well different dispersal dynamics crossed with NM, MSS, and SSS metacommunity dynamics could maintain initial metacommunity composition.…”

“…Satellite imagery ( Figure 2) was used to derive a two-dimensional map ( Figure 4A) highlighting the distribution of photosynthetic mat communities throughout the watershed of Lake Fryxell (i.e., Fryxell Basin). Recent studies have demonstrated that satellite data and the use of common spectral parameters like the Normalized Difference Vegetation Index (NDVI) can effectively identify the distribution of these cyanobacterial mats in the MDV (Salvatore, 2015;Salvatore et al, 2020). NDVI is a commonly used spectral parameter in remote sensing that is used to identify the distribution and relative photosynthetic capacity of vegetation.…”

“…The product of this ratio is a value between −1 and +1, with higher values representing greater mat density, photosynthetic activity, or the presence of otherwise spectrally dominant vegetation. While NDVI values are nonunique in most terrestrial ecosystems due to the heterogeneity in photosynthetic species, higher NDVI values are far more closely linked to the presence and areal coverage of cyanobacterial mats in the MDV due to the relative simplicity of these ecosystems (Salvatore et al, 2020). Here, we specifically use NDVI to identify likely patches of cyanobacterial mat communities in the Fryxell Basin to provide a proxy for the spatial distribution of diatom habitats.…”

“…Here, we specifically use NDVI to identify likely patches of cyanobacterial mat communities in the Fryxell Basin to provide a proxy for the spatial distribution of diatom habitats. High-resolution WorldView-2 data were processed in accordance with the methods described in Salvatore (2015) and Salvatore et al (2020). Data were calibrated to surface reflectance using the Dark Object Subtraction and Regression (DOS-R) methods before NDVI was derived.…”

“…Here, freshwater habitats often harbor dense cyanobacterial mats, which are the major primary producers in the landscape (McKnight et al, 1998). Because these ecosystems lack vascular plants, data products derived from satellite imagery (e.g., NDVI maps) can be used to map the distribution of such mats throughout the landscape (Salvatore et al, 2020). In the McMurdo Dry Valleys (MDV) of East Antarctica, "orange" and "black" mat types are common in and around glacial meltwater streams.…”