Remote monitoring of hypersaline environments in San Francisco Bay, CA, USA

Abstract

As part of a historic remediation project, approximately 61 km 2 of salt evaporation ponds in the southern portion of San Francisco Bay, CA (USA) are scheduled for restoration to natural tidal marsh habitat over the next several decades. We have investigated the correlation of remotely sensed infrared spectral information with in situ field measurements and sampling, and evaluated the usefulness of a remote sensing approach to monitor salinity and population distributions of microbial communities in the hypersaline ponds. The Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) instrument operated by the Jet Propulsion Laboratory has created a ten-year archive of spectral information concerning these ponds. We utilized spectral signatures of microbial populations that are sensitive to salinity, and trained a supervised classification algorithm to identify physical parameters from an AVIRIS scene based upon microbe spectra gathered in the field using a portable visible to near-infrared (VNIR) spectrometer. Our results indicate that automated analyses of hyperspectral observations are capable of detecting variations in microbial populations and discriminating corresponding salinity levels.

Nonphotosynthetic Pigments as Potential Biosignatures

“… Diurnally averaged spectral albedos from the Virtual Planetary Laboratory's 3-D Earth model for March 18–19, 2008, under a realistic scenario (blue) from Robinson et al ( 2011 ) and a scenario that is identical with the exception that the spectral reflectance of the ocean surface has been replaced by the spectral reflectance of a pigmented halophile-dominated saltern pond from work by Dalton et al ( 2009 ) (pink). Major gaseous absorption features are labeled.…”

“…The reflectance spectrum for the halophile-dominated pond (see Fig. 1c ) was taken from the work of Dalton et al ( 2009 ), which provides reflectance spectra of the San Francisco salt ponds measured in situ and therefore includes the spectral effects of both the pigmented organisms contained within the pond and the overlying layers of water. The other surface reflectances are from the USGS and ASTER spectral libraries (Clark et al , 2007 ; Baldridge et al , 2009 ).…”

“… Spectral reflectances of abiotic and biotic surfaces from the USGS (Clark et al , 2007 ); and ASTER (Baldridge et al , 2009 ) spectral libraries from 0.35 to 1.2 μm. The halophile salt pond's spectral reflectance is from work by Dalton et al ( 2009 ). Note the water absorption features in the bacterial mat, red algae water, and halophile salt pond cases.…”

Progress in the Remote Sensing Monitoring of the Ecological Environment in Mining Areas

“…Unlike direct monitoring of animals and plants, commercial sensors cannot directly identify the physiological status of microorganisms. At present, research on the remote sensing monitoring of microorganisms involves two aspects: one is to infer the physiological status of microorganisms from other organisms, soil quality, and water quality, and the other is to establish the microbial distribution model [57][58][59]. It should be noted that the remote sensing monitoring of microorganisms and ecological communities is expensive and still in the experimental stage [57].…”

Early evolution of purple retinal pigments on Earth and implications for exoplanet biosignatures

“…For example, halophilic communities present in saltern ponds possess a peak in brightness near ∼680 nm due to increasing reflectivity of bacteriorhodopsin and carotenoid pigments from the green to the red combined with strong water absorption at the reddest wavelengths ( Fig. 6b; also see Dalton et al, (2009)). Importantly, the brightness of halophilic pigments at orange and red wavelengths confers a detectability advantage over chlorophyll-containing cyanobacteria and algae suspended in water, because chlorophyll's high infrared reflectivity is counteracted by water vapour absorption, while chlorophyll is most absorptive at wavelengths where water is relatively transparent.…”