Jones, D.O.B.

New methods are needed for the study of coral reefs, as they are changing rapidly. Satellite remote sensing has become a common method for benthic mapping with advances in satellites and sensors and as methods are devised to account for atmospheric and water-column effects. Images from the QuickBird satellite have proven useful in reef mapping. Sand was distinguished from coral with an overall accuracy of 75% on the shallow reef off of the Caribbean island of Bonaire. Coral and sand had user accuracies of 50% and 90%, respectively. Increased samples of field-collected data would further increase the accuracies of such classifications.

The island of Bonaire is a long-established Marine Protected Area (MPA), the reefs of which were extensively mapped in the early 1980s. Satellite remote sensing techniques were used to construct reef maps for 2008–2009. Metrics describing the spatial structure of coral habitat at the landscape scale – including coral cover, fragmentation, patch size and connectivity between patches – were calculated and compared between these two time periods. Changes were evaluated in and out of the MPAs and in areas exposed and sheltered from storm damage. Overall, coral cover has declined during the past three decades, being replaced by sand, but the decline has not been as drastic as elsewhere in the Caribbean. Fragmentation of the reef habitat has occurred, resulting in smaller and more disparate patches, but these changes were not associated with exposure along the coastline. However, total coral cover was maintained in sheltered areas, whereas it declined along exposed shorelines. Human protection of reefs by marine reserves had variable effects on coral cover and fragmentation. One of two no-diving marine reserves showed increases in coral cover accompanied by decreases in the number of patches of coral and an increase in the size of individual patches over the time period, while the second reserve exhibited the opposite trend. Advances in satellite remote sensing techniques allow for a more rapid assessment of changes in reefs at the landscape level, which can be used to identify spatial changes in the reef environment, including areas of coral decline.