A prototype in-water laser line-scanning multispectral fluorescence imaging system was evaluated for its ability to provide data that could be used to determine the quantitative distribution and abundance of various functional groups on coral reefs. The system collected fluorescence imagery in three spectral bands with 1 cm 2 resolution at sites in Florida and the Bahamas. Fluorescence excitation was at 488 nm, and imagery was collected in emission bands centered at 520, 580, and 685 nm. Ground truth data on bottom cover was collected by divers using conventional line transect and photographic quadrat methods. A set of classification rules based on the relative signal levels in the three fluorescence channels was developed to assign the image pixels to functional groups. Once the image was classified, percent cover data for the groups were computed for the full image and for subsets of the image chosen to simulate line transect, grid survey, and photographic quadrat surveys. The statistics of percent cover of various bottom types derived from the fluorescence image compared favorably with those determined by diver survey techniques. The results demonstrate that fluorescence imaging has the long-term potential to provide coverage of large spatial areas of coral reefs at high resolution, with automated classification and quantification of functional groups in the image. AcknowledgmentsThis work was supported by grants to C.H.M., M.P.L., M.P.S., and B.C. from the Coastal Benthic Optical Properties program of the Environmental Optics Program, Office of Naval Research, and to M.P.C. from the U.S. Man and the Biosphere Program. We thank the Caribbean Marine Research Center at Lee Stocking Island, Bahamas, Florida Keys National Marine Sanctuary (FKNMS), National Oceanic and Atmospheric Administration (NOAA), Harbor Branch Oceanographic Institution, and the crews of the R/V Edwin Link, NOAA ship Ferrel, the FKNMS R/V Cool Hand, and the Florida Institute of Oceanography R/V Suncoaster for field support.

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A prototype underwater laser scanner imaging system has been built and tested in a laboratory test tank. Simultaneous tests were conducted with two state -of -the -art commercial underwater television cameras to quantify the performance of the prototype scanner relative to conventional imaging systems. Tests were conducted with the clarity of the water adjusted to match the clarity of clear deep ocean water, beam attenuation coefficient c = 0.10 /meter, and the clarity of typical coastal water, c = 0.39 /meter. The scanner system used a 40 milliwatt (combined 488 nanometer and 514.5 nanometer) Argon ion laser as the light source and a 2 -inch diameter photo -multiplier tube (PMT) as the detector. The PMT had an unrestricted field -of -view. No scan synchronization, range gating, or other advanced techniques were used.

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