December 2005 AVIRIS Mission: Puerto Rico & U.S. Virgin Islands
The 2005 Caribbean Bleaching Event
In mid-December 2005, in response to one of the most devastating regional-scale coral bleaching events on record in the Caribbean, NASA Ames Research Center scientists teamed with scientists from NOAA’s Coral Reef Conservation and Biogeography Programs, the University of Puerto Rico at Mayagues and the National Park Service (NPS) of the US Virgin Islands to investigate the status of coral bleaching in the Caribbean. This collaborative effort was in support of the US Coral Reef Task Force’s (USCRTF) resolution passed in November 2005 to mobilize Task Force agencies to assess the coral reef bleaching event, coral mortality, coral recovery, and the ecological impact of the September-October 2005 coral bleaching event in Puerto Rico (PR) and the US Virgin Islands (USVI).
This assessment consisted of collection of hyperspectral data using the NASA Airborne Visible Infrared Imaging Spectrometer (AVIRIS) by NASA Jet Propulsion Laboratory scientists and the NASA Suborbital Science Program high resolution Digital Camera System (DCS) supported by UC Santa Cruz Airborne Sensor Facility scientists with field data collection by NASA Ames researchers in collaboration primarily with University of Puerto Rico coral reef researchers, NOAA’s Biogeography Program researchers, and the National Park Service (NPS) researchers in the USVI and coordinated with the USCRTF steering committee.
The AVIRIS and DCS were flown on the NASA Wallops Twin Otter plane at approximately 3.5 km altitude. AVIRIS spatial resolution was approximately 3.5 m and the DCS was <1m. Further, the NASA Ames Ecosystem Science and Technology Branch provided a hyperspectral sensor that was accompanied by the Fireball Information Technologies Kodak camera on board a Cessna plane in Puerto Rico. Fireball operated the sensors on the Cessna at approximately 1,500-3,000 ft (450-920 m) altitude.
The goal of this research is to use practical applications in remote sensing to describe and monitor biological and physical properties of reefs in the Caribbean affected by the massive bleaching event September-October 2005. The importance of this research is that we will be concentrating on aspects that enhance both understanding and prediction of reef status in terms of the extent of bleached corals, coral mortality, evidence of recovery, evidence of algal overgrowth, and biodiversity using airborne image data and field measurements. Further, with the listing of Acroporids (elkhorn and staghorn coral) as threatened under the US Endangered Species Act, we have included known transects with Acroporid stands from a NASA Ames/University of PR at Mayaguez (UPRM) project as well as long term projects by NOAA and the NPS in the USVI.
Collaboration with the U.S. Coral Reef Task Force Agencies and Institutions
In addition to the NASA AVIRIS and camera data, we are collaborating with NOAA’s Biogeography Program researchers to co-analyze acquired satellite multispectral (Ikonos) data along with December 2005 and previous field measurements. AVIRIS baseline data was collected in August 2004 over Puerto Rico and Vieques Is. (PR) and for December 2005 for Puerto Rico, St. Croix (Buck Island), and St. John, USVI. Ikonos data collects have been identified for acquisition by NOAA for La Parguera, PR and for the USVI during the bleaching event and during our December 2005 deployment. Extensive field data has been collected during the bleaching event and following the event by scientists of agencies and institutions having membership in the USCRTF. This remote sensing data will be coupled with a wealth of long-term field measurements at established sites of biological data in Puerto Rico and the USVI by NASA Ames, NOAA, NPS, Univ. of Puerto Rico, and USCRTF member agencies and collaborating institutions. This research deployment will also contribute to research on ecological structure and benthic habitat biodiversity of coral reefs. Further, the proposed AVIRIS data, having high spatial and spectral resolution information, will be used along with Ikonos satellite data and integrated with in situ measurements from diving surveys and autonomous underwater vehicle (AUV) photo transects by US CRTF member agencies and collaborating institutions.
Field Data Collection
Biological information data collection by NASA, NOAA, and the University of Puerto Rico includes bio-optical properties of the water column and of reef bottom types including bleached coral species, percent cover of benthic types, coral patchiness, distance between patch reefs, rugosity, and species abundance and distribution. Spectral characteristics of bleached, dead, diseased, pale, algal covered, and living coral were collected along with other dominant bottom types. Spatial patterns and connectivity of patch reefs and associations with other benthic habitats will be revealed through analyses of remote sensing and in situ data for characterizing ecological structure. Plot and AUV transect measurements of biodiversity will be related to the remote sensing data with particular attention to error propagation in scaling.
A critical contribution of this work is to map the distribution and health status of the declining Acropora species (elkhorn and staghorn coral and associated hybrid), an important dominant reef builder in the Caribbean and Florida, and is present in our study areas. The NASA team is well positioned to contribute to this research having already obtained unique data sets (airborne and field) in 2004 and 2005 together with long-term research data acquired in the La Parguera area by the University of Puerto Rico and NOAA. In the USVI, a wealth of research data has been previously acquired by NOAA and the University of Puerto Rico with the Woods Hole Oceanographic Institution autonomous underwater vehicle (AUV) team.
Methods for Field Data Collection
In collaboration with UPRM, NOAA’s Biogeography Program, and USVI NPS we performed field sampling to collect data for input into atmospheric correction and calibration of the AVIRIS data. Further spectra were collected underwater with a hand-held spectroradiometer (GER 1500, SpectraVista Corp.) to quantify light attenuation coefficients for water column characterization. Spectra of dominant benthic types (e.g., corals, algae, sand) and at points along transects were collected to develop spectral libraries for performing benthic classification of the AVIRIS data. The spectral analysis and benthic classification will assist in the assessment of coral bleaching extent, coral mortality, algal overgrowth, and coral recovery.