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Remote Sensing of Coral Reefs: Testing the Waters at Biscayne National Park

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Biscayne National Park panoramic image
Biscayne National Park. Panoramic image courtesy of USGS South Florida Virtual Tour: Biscayne National Park.

NASA Experimental Advanced Airborne Research Lidar (EAARL)
EAARL: The NASA Experimental Advanced Airborne Research Lidar (EAARL) collected georectified digital aerial photographs concurrent with high-resolution lidar views of water-column properties and underwater topography. Here, shallow patch reefs are visible in both the photomosaic and the lidar raster image (cross section).
South of Miami on Florida's Atlantic coast, at the north end of the Florida coral-reef tract, lies Biscayne National Park. It is 95 percent submerged, with 700 km2 of mangrove forest, shallow estuarine waters, uninhabited keys, and popular coral reefs. The reef tract is famous as a classic field area for studies of Pleistocene and Holocene carbonates, and the park itself was the site of some of the earliest studies in airborne remote sensing.

One current research project in the park seeks to further develop remote-sensing methods appropriate for shallow-bottom areas. In August 2002, scientists from several institutions gathered at Biscayne National Park for 10 days of cooperative fieldwork organized by U.S. Geological Survey (USGS) scientists John Brock and Tonya Clayton. This fieldwork was part of an ongoing collaboration with Wayne Wright of the National Aeronautics and Space Administration (NASA), in support of the development and evaluation of a new airborne sensor designed with coral-reef environments in mind. Thanks to Richard Curry, Biscayne National Park's science coordinator, the park has served as a primary study site for this and several other USGS science projects (see previous Sound Waves articles at the end of this story).

The purpose of this particular mission was to collect new kinds of lidar (light detection and ranging) and photographic data from an aircraft, while boatborne collaborators simultaneously collected "sea-truthing" acoustic and optical data over selected reef areas. (Airborne lidar uses laser light to efficiently and accurately measure the elevations of features on land and in shallow water.)

At center stage was the NASA Experimental Advanced Airborne Research Lidar (EAARL), developed by Wayne and flown on a Cessna 310 by pilot Virgil Rabine and copilot Wayne.

On the ground, Amar Nayegandhi (USGS) and NASA interns Conan Noronha (NASA/University of Southern California) and Enils Bashi (NASA/Salisbury University) provided real-time programming and aircraft-data processing. NASA intern Kevin Riordan (NASA/University of South Carolina) collected terrestrial ground-truthing data, while USGS intern Lance Mosher (USGS/Eckerd College) manned a global-positioning-system (GPS) base station at Adams Key.

Emmanuel Boss monitors the descent of the optics package
Emmanuel Boss monitors the descent of the optics package. The orange floats are mounted atop the package frame to achieve near-neutral buoyancy and a controlled, slow descent of the sensors through the water column. Coral-reef substrate is visible through the clear waters.
The crew of the "optics boat" included Tonya, John, Don Hickey (all of the USGS), and Emmanuel Boss (University of Maine). One primary function of this platform was the deployment of a small multisensor package assembled to measure several water-column optical properties, such as absorption and attenuation of light, and various indexes of light scattering. At selected sites, detailed characterizations of the sea floor were made, along with measurements of light upwelling from the sea floor and the water column. While towing the optics package on horizontal transects, the boat also towed a video camera to take pictures of the seagrasses, corals, and sand on the bottom. Zhiqiang Chen (University of South Florida) spent some time on the boat and, in addition, processed water samples for chlorophyll concentration and for light absorption by various water-column constituents.

The National Coral Reef Institute (NCRI) provided the "acoustics boat." The crew here included Bernhard Riegl (NCRI), BJ Reynolds (USGS), Ryan Moyer (NCRI), and Brian Walker (NCRI). Sonar data collected at 50- and 200-kHz frequencies are being used to map bathymetry and bottom type. Coincident towed video footage was collected in selected areas. BJ pulled double duty by also coordinating the field GPS measurements.

One highlight of the trip was a field trip from the field trip: after several long(!) days in the searing subtropical sun, everyone took a day off from the open waters (and skies) and met at the Marathon airport to visit the aircraft and view the EAARL operations. USGS botanist Tom Smith, who happened to be working in Everglades National Park at the time, also joined the excursion, which was a welcome and well-earned opportunity to share some shade, data, and veggieburgers.

Rob Coulson accompanies the Morpheus on its Anniversary Reef mission
Rob Coulson accompanies the Morpheus (circled) on its Anniversary Reef mission. (This was our best weather day ever!) Image courtesy of Joe Lambiotte, Florida Atlantic University.
During the final few days of the field trip, colleagues from Florida Atlantic University joined in. The star of this show was the Morpheus, a modular autonomous underwater vehicle (AUV) designed to collect video and sidescan-sonar data. Edgar An, assisted by Rob Coulson, Joe Lambiotte, Gabriel Grennon, Abby Chronister, and Capt. Bob Franks, deployed the Morpheus on two missions: the first over Anniversary Reef, a shallow reef that serves as one focus area of the larger USGS project; and the second, under Richard's guidance, over deeper reef areas. The AUV provided a rare opportunity to obtain a close-up look at depths inaccessible to divers.

This trip was made possible by the generous support of many folks both in the field and in the lab. In addition to the participation noted above, Richard provided a park boat that was ideal for deploying the optics package, as well as dive tanks and air arrangements that greatly facilitated data collection. Shay Viehman (Biscayne National Park) also assisted with the many logistic arrangements and details. Pam Reid and Art Gleason (University of Miami) generously provided laboratory space and many liters of optically clean water (a rare commodity!) for essential instrument calibrations. Charlie Mazel (Physical Sciences, Inc.) and Chuanmin Hu (University of South Florida) facilitated reflectance measurements. The contributions of these folks and all others who pitched in to make the trip a success are gratefully acknowledged.

Related Sound Waves Stories
Ground-Truthing Coral-Reef Maps Produced from Remote-Sensing Data
May 2002
Core Drilling in Biscayne National Park
July 2001
NASA EAARL Lidar Test at Wallops Flight Facility
April 2001
USGS Collaborates with Biscayne National Park on Coral-Reef Research
August 2000

Related Web Sites
South Florida Information Access (SOFIA)
U.S. Geological Survey (USGS)
National Coral Reef Institute
Nova Southeastern University Oceanographic Center
Biscayne National Park
U.S. National Park Service

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in this issue: Fieldwork cover story:
Seagrass Restoration in Tampa Bay

Tracking Pintail-Duck Population Decline

Remote Sensing of Coral Reefs at Biscayne National Park

Exploring the Puerto Rico Trench

Research Assateague Island Restoration

Outreach Dedication of New Lake Mead Research Vessel

Meetings Sea-Level Change Workshop

The Need for Better Scientific Understanding of Sea-Level Change

Remote-Sensing at Cape Cod National Seashore

Familiar Faces at Fall Meetings

Giving Interns a View of Science Career Paths

Staff & Center News Visiting Engineer Brings Modeling Expertise

Parsons Succeeds Lee as Acting Chief Scientist for WRCMG Team

Publications November Publications List

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