A MULTIVARIATE APPROACH TO ESTABLISH HABITAT CLASSIFICATIONS IN A CORAL REEF ECOSYSTEM USING LANDSAT 7 SATELLITE IMAGERY AT TURNEFFE A TOLL, BELIZE, CENTRAL AMERICA.

Abstract

The use of multivariate cluster and discriminant function analysis of ground truth data and LANDSAT 7 satellite imagery (23 May 2000) was examined to classify tropical marine habitats at Tumeffe Atoll, Belize. Ground truth data were obtained using SCUBA, digital video and the global positioning system in June 2000 and July 2001. Ground trothing was done by swimming along eleven 150- to 300-meter transect lines located on the southeastern side of the atoll and videotaping bottom habitat from 1.5 m above the bottom at 30-meter intervals (126 sites). The still images were displayed on a 21cm x 29 cm flat-screen monitor, overlaid with a 20-cell grid (5.25 cm x 5.80 cm cells), and% cover of seven bottom cover classes was computed. Using hierarchical cluster analysis of water depth and habitat percent cover data, the 126 sites were grouped into three distinct habitat clusters (sand, seagrass and coral reef habitats). A discriminant analysis of the sites was performed using LANDSAT digital values in enhanced thematic mapper (ETM+) Bands 1, 2, 3, and 4 (the only ones that penetrate water) as predictors of habitat cluster membership. When predicting the habitat class of the sites used for training, coral reef areas were correctly classified 100%, seagrass areas 80 %, and sand dominated areas 77 % of the time. Using the classification function from the discriminant analysis, the LANDSAT 7 image was recoded to create a habitat map of the region surrounding Tumeffe Atoll, showing coral reef, seagrass, and sand-dominated regions. Using the recoded map, new ground truth sites were visited in 2002 to record depth and benthic classification. The recoded map had an overall accuracy of 60% and a tau coefficient of 52.47%. Such maps can be used to identify essential fish habitat areas and study changes in habitat area over time.