Mapping reef terrain roughness and benthic habitat complexity in the Pamegaran Island, Kepulauan Seribu National Marine Park

Abstract

The formation of coral cays in the Kepulauan Seribu Marine Parks, Jakarta Special Capital Region, is the result of patch reef evolution which linked to the geology of sediment accretion, including the ecology of coral growth and competition of benthic community. This study aims to map the level of reef complexity in Pamegaran Island using Benthic Terrain Modeler. Field observation to monitor benthic communities in four stations at 3- and 5- meter depth was combined with SPOT-7 image processing to evaluate in situ rugosity, 3-dimensional bathymetry and benthic habitat classification. The results of this study revealed low degree of terrain complexity as results of habitat degradation and dominant benthic class of sand. Classification of reef benthic habitat resulted in five classes, namely sand (Sd= 126.65 ha), seagrass (Sg= 35.29 ha), bare rubble (Rb= 32.68 ha), reefs dominated by dead corals (DC=3.16 ha) and dead coral with algae (DA= 20.50 ha); with 67.21% score of overall accuracy (OA). In situ rugosity at 5 m was higher than 3 m, as result of higher coverage of live corals particularly in the east site. Similar profile was shown for rugosity index, which reflects ratio between surface to planar area and seafloor gradient along the reef slope. Finally, positive correlation between reef surface and in situ rugosity implies the importance of live coral communities in supporting complex terrain and benthic habitat in the patch reef environment.