Model for deriving benthic irradiance in the Great Barrier Reef from MODIS satellite imagery

Magno-Canto, Marites M., McKinna, Lachlan I.W., Robson, Barbara J., and Fabricius, Katharina E. (2019) Model for deriving benthic irradiance in the Great Barrier Reef from MODIS satellite imagery. Optics Express, 27 (20). A1350-A1371.

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We demonstrate a simple, spectrally resolved ocean color remote sensing model to estimate benthic photosynthetically active radiation (bPAR) for the waters of the Great Barrier Reef (GBR), Australia. For coastal marine environments and coral reefs, the underwater light field is critical to ecosystem health, but data on bPAR rarely exist at ecologically relevant spatio-temporal scales. The bPAR model presented here is based on Lambert-Beer’s Law and uses: (i) sea surface values of the downwelling solar irradiance, Es(λ); (ii) high-resolution seafloor bathymetry data; and (iii) spectral estimates of the diffuse attenuation coefficient, Kd(λ), calculated from GBR-specific spectral inherent optical properties (IOPs). We first derive estimates of instantaneous bPAR. Assuming clear skies, these instantaneous values were then used to obtain daily integrated benthic PAR values. Matchup comparisons between concurrent satellite-derived bPAR and in situ values recorded at four optically varying test sites indicated strong agreement, small bias, and low mean absolute error. Overall, the matchup results suggest that our benthic irradiance model was robust to spatial variation in optical properties, typical of complex shallow coastal waters such as the GBR. We demonstrated the bPAR model for a small test region in the central GBR, with the results revealing strong patterns of temporal variability. The model will provide baseline datasets to assess changes in bPAR and its external drivers and may form the basis for a future GBR water-quality index. This model may also be applicable to other coastal waters for which spectral IOP and high-resolution bathymetry data exist.

Item ID: 60783
Item Type: Article (Research - C1)
ISSN: 1094-4087
Copyright Information: © 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Funders: James Cook University (JCU), Australian Institute of Marine Science (AIMS), National Environmental Research Program (NERP)
Projects and Grants: NERP Tropical Water Quality Hub 2.3.1
Date Deposited: 04 Aug 2021 00:11
FoR Codes: 37 EARTH SCIENCES > 3708 Oceanography > 370899 Oceanography not elsewhere classified @ 20%
40 ENGINEERING > 4013 Geomatic engineering > 401304 Photogrammetry and remote sensing @ 60%
51 PHYSICAL SCIENCES > 5103 Classical physics > 510302 Classical and physical optics @ 20%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180501 Assessment and management of benthic marine ecosystems @ 50%
18 ENVIRONMENTAL MANAGEMENT > 1802 Coastal and estuarine systems and management > 180201 Assessment and management of coastal and estuarine ecosystems @ 50%
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