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Article

Coral Bleaching Detection in the Hawaiian Islands Using Spatio-Temporal Standardized Bottom Reflectance and Planet Dove Satellites

Center for Global Discovery and Conservation Science (GDCS), Arizona State University, Tempe, AZ 85281, USA
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Remote Sens. 2020, 12(19), 3219; https://doi.org/10.3390/rs12193219
Received: 25 August 2020 / Revised: 22 September 2020 / Accepted: 1 October 2020 / Published: 2 October 2020
(This article belongs to the Special Issue Advances in Remote Sensing of Coral Reefs)
We present a new method for the detection of coral bleaching using satellite time-series data. While the detection of coral bleaching from satellite imagery is difficult due to the low signal-to-noise ratio of benthic reflectance, we overcame this difficulty using three approaches: 1) specialized pre-processing developed for Planet Dove satellites, 2) a time-series approach for determining baseline reflectance statistics, and 3) a regional filter based on a preexisting map of live coral. The time-series was divided into a baseline period (April-July 2019), when no coral bleaching was known to have taken place, and a bleaching period (August 2019-present), when the bleaching was known to have occurred based on field data. The identification of the bleaching period allowed the computation of a Standardized Bottom Reflectance (SBR) for each region. SBR transforms the weekly bottom reflectance into a value relative to the baseline reflectance distribution statistics, increasing the sensitivity to bleaching detection. We tested three scales of the temporal smoothing of the SBR (weekly, cumulative average, and three-week moving average). Our field verification of coral bleaching throughout the main Hawaiian Islands showed that the cumulative average and three-week moving average smoothing detected the highest proportion of coral bleaching locations, correctly identifying 11 and 10 out of 18 locations, respectively. However, the three-week moving average provided a better sensitivity in coral bleaching detection, with a performance increase of at least one standard deviation, which helps define the confidence level of a detected bleaching event. View Full-Text
Keywords: coral bleaching; coral reef; Hawaiian Islands; remote sensing; Planet Dove coral bleaching; coral reef; Hawaiian Islands; remote sensing; Planet Dove
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MDPI and ACS Style

Xu, Y.; Vaughn, N.R.; Knapp, D.E.; Martin, R.E.; Balzotti, C.; Li, J.; Foo, S.A.; Asner, G.P. Coral Bleaching Detection in the Hawaiian Islands Using Spatio-Temporal Standardized Bottom Reflectance and Planet Dove Satellites. Remote Sens. 2020, 12, 3219. https://doi.org/10.3390/rs12193219

AMA Style

Xu Y, Vaughn NR, Knapp DE, Martin RE, Balzotti C, Li J, Foo SA, Asner GP. Coral Bleaching Detection in the Hawaiian Islands Using Spatio-Temporal Standardized Bottom Reflectance and Planet Dove Satellites. Remote Sensing. 2020; 12(19):3219. https://doi.org/10.3390/rs12193219

Chicago/Turabian Style

Xu, Yaping, Nicholas R. Vaughn, David E. Knapp, Roberta E. Martin, Christopher Balzotti, Jiwei Li, Shawna A. Foo, and Gregory P. Asner. 2020. "Coral Bleaching Detection in the Hawaiian Islands Using Spatio-Temporal Standardized Bottom Reflectance and Planet Dove Satellites" Remote Sensing 12, no. 19: 3219. https://doi.org/10.3390/rs12193219

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