Liane Guild, Brad Lobitz, Randy Berthold, Jeremy Kerr Biospheric Science Branch, NASA Ames Research Center, CA Roy Armstrong, James Goodman University of Puerto Rico at Mayaguez, PR Collaborators: AVIRIS Team at NASA JPL Airborne Science and Technology Lab at NASA Ames Funding: Interdisciplinary Research in Earth Science NASA Ocean Biology and Biogeochemistry Program Contact: Coral Reef Bleaching and Threats to Biodiversity in Puerto Rico

Use NASA’s 2005 AVIRIS imagery over La Parguera, Puerto Rico to map coral reef benthic types and change Map the distribution of the threatened Acropora species (A. cervicornis and A. palmata) along bathymetric zones Use AVIRIS data and field measurements to assess the ecological impact of the 2005 coral bleaching event in Southwestern Puerto Rico Establish permanent reef monitoring transects to track change Improve the interpretation of reef habitat variability and biodiversity Objectives

NASA AVIRIS Mission of the 2005 Caribbean Coral Reef Bleaching Event AVIRIS flight lines over La Parguera, Puerto Rico December 12-13, 2005 Twin Otter Platform, Altitude ~3.5 km Pixel Size 2.4 m

Reef benthic type spectra Photogrids GPS Depth Water optical properties Field Measurements GER spectroradiometer in an underwater housing

Hyperspectral Profiles Satlantic HyperPro measures: –Lu –upwelling radiance –Ed –downwelling irradiance –Es – surface Ed Spectral range 350 – 800 nm Calculates Kd (λ) from Ed profiles Data obtained during AVIRIS over flights Monthly sampling to address temporal variability

LiDAR Bathymetry and reflectivity products ADS Mk II Airborne System April 2006-May 2007 Bathymetry to 50 m Spatial Resolution 4m

Processing Steps Atmospheric correction – Tafkaa (Gao et al. 2000, Montes et al. 2001, 2003) Sun glint removal (Hedley et al. 2005) Semi-analytical model (Lee et al. 1996, 1998, 1999) J. Goodman’s implementation of this model Image Preprocessing Anomaly Corrections Glint Removal Atmospheric Correction Inversion Model Semi-Analytical Input Parameters Absorption Properties Bottom Reflectance Linear Unmixing Model Inversion Output Water Constituent Properties Bottom Albedo (550 nm) Bathymetry RMSE Unmixing Output Reef, Algae, Sand Distribution RMSE Spectral Endmembers Reef, Algae, Sand Field Spectra Forward Model Semi-Analytical AVIRIS

2005 AVIRIS: Unmixing Model J. Goodman (UPRM) Forward Model Preprocessed AVIRIS Imagery Spectral Input Parameters Aquatic Absorption Properties Generic Bottom Reflectance Image Geometry Explicit pixel by pixel subsurface angles View (AVIRIS) Illumination (solar) Inversion Output Water Properties Bathymetry Unmixing Model Spectral Endmembers Unmixing Output Benthic Composition Sand Algae Coral

R b = (1/0.54) R rs (z = a) – (1 – e -2kz ) R w e -2kz R rs (z = a) reflectance just above the water surface (1/0.54) corrects for transmittance of the air/water interface and the refractive index R b is substrate reflectance k is the attenuation coefficient of the water body R w is the water column reflectance in optically deep waters z is depth (from LiDAR) All terms except z are wavelength specific Water Column Corrections R. Armstrong (UPRM)

Effects of Water Column Correction – Sand Target Atmospherically corrected pixel over sand target In situ percent reflectance of sand target (red line) AVIRIS water column corrected pixel (blue line) Depth 2.5 m Percent Reflectance

Effects of Water Column Correction - Sea grass Target Atmospherically corrected pixel over seagrasses In situ percent reflectance of sea grass target (red line) AVIRIS water column corrected pixel (blue line) Depth 2.5 m Percent Reflectance

Effects of Water Column Correction – Coral Target Atmospherically corrected pixel over coral target In situ percent reflectance of typical coral endmember (red line) AVIRIS water column corrected pixel of mixed living/dead corals and sand (blue line) Depth 0.5 m Percent Reflectance

Temporal Changes in Benthic Composition and Diversity San Cristobal Reef, La Parguera Using field transect data from: August 2005 December 2005 November 2007

Trends in Reef Cover Type

Trends in Coral Cover

Acropora cervicornis (staghorn coral) Transects

Changes in Biodiversity Pre-bleaching event (August 2005):0.70*0.60** Post-bleaching and mortality (November 2007):1.61*0.22** * = calculated as each coral species cover as a percent of total coral cover ** = calculated as each coral species cover as a percent of overall cover Acroporid dominance in 2005, before the bleaching event, was 98%. This dominance diminished to 2% in 2007 accounting for the increase in diversity when only coral species are included in the index calculations. When other reef benthic components (sponges, gorgonians, macroalgae) are taken into account, there was a dramatic decrease in coral diversity according to the Shannon-Wiener Index. The Shannon-Wiener Diversity Index is a measurement of biodiversity. This index takes into account the number of species and the evenness of the species. Shannon-Wiener Index

Summary  AVIRIS data have been atmospherically corrected including: Stray-light anomaly suppression Removal of sun glint  Unmixing analysis is in progress: Using spectral endmembers of coral, sand, and algae Analysis performed for depth range 0-10 m Use MESMA for unmixing and compare results  Next steps : Finish field data analysis for all years Implement water column corrections and use of spectral library Accuracy assessment of benthic composition classification Complete reef degradation and “biodiversity” analysis