HR: 16:00h
AN: OS24A-01    [Abstracts]
TI: Water clarity in the Florida Keys, USA, as observed from space (1984-2002)
AU: * Palandro, D A
EM: david.palandro@myfwc.com
AF: Florida Fish and Wildlife Research Institute, 100 8th Ave SE, St. Petersburg, FL 33701, United States
AU: Hu, C
EM: hu@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave S, St. Petersburg, FL 33710, United States
AU: Andrefouet, S
EM: serge.andrefouet@noumea.ird.nc
AF: UR Coreus - Institut de Recherche pour le Développement, BP A5, Nouméa cedex, 98848, New Caledonia
AU: Muller-Karger, F E
EM: carib@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave S, St. Petersburg, FL 33710, United States
AU: Hallock, P
EM: muller@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave S, St. Petersburg, FL 33710, United States
AB: Landsat TM and ETM+ satellite data were used to derive the diffuse attenuation coefficient (Kd, m-1), a measure of water clarity, for 29 sites throughout the Florida Keys Reef Tract. A total of 28 individual Landsat images between 1984 and 2002 were used, with imagery gathered every two years for spring seasons and every six years for fall seasons. Useful information was obtained by Landsat bands 1 (blue) and 2 (green), except when sites were covered by clouds or showed turbid water. Landsat band 3 (red) provided no consistent data due to the high absorption of red light by water. Because image sampling represented only one or two samples per year on specific days, and because water turbidity may change over short time scales, it was not possible to assess temporal trends at the sites with the Landsat data. Kd values in band 1 were higher in the spring (mean spring = 0.034 m-1, mean fall = 0.031 m-1) and band 2 were higher in the fall (mean spring = 0.056 m-1, mean fall = 0.058 m-1), but the differences were not statistically significant. Spatial variability was high between sites and between regions (Upper, Middle and Lower Keys), with band 1 ranges of 0.019 m-1 – 0.060 m-1 and band 2 ranges of 0.036 m-1 – 0.076 m-1. The highest Kd values were found in the Upper Keys, followed by the Middle Keys and Lower Keys, respectively. This result must be taken in context however, two Middle Keys sites were found to be inconsistent due to high turbidity, obscuring the benthos and altering our assumption of a visible seafloor, which the algorithm is dependent upon. If all Middle Keys data were valid it is likely that this region would have the highest Kd values for both bands. The Landsat-derived Kd values, and inherent variability, may be influenced by the dominant water mass associated with each Florida Keys region, as well as localized oceanic variables. The methodology used here may be applied to other reef areas and used with satellites that offer higher temporal resolution to assess temporal change and variability.
DE: 4220 Coral reef systems (4916)
DE: 4264 Ocean optics (0649)
DE: 4271 Physical and chemical properties of seawater
DE: 4275 Remote sensing and electromagnetic processes (0689, 2487, 3285, 4455, 6934)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting