Vertical distribution and effect of the depth on growth form and genus of hard coral on coral reef in Bunaken Island, North Sulawesi, Indonesia

Abstract

Bunaken Island generally has a 90° slope and it forms like an underwater wall. However, there are several locations in Bunaken Island that have a more gradually inclined slope. This study was aimed to identify the effect of depth and slope gradient toward vertical distribution on growth forms and genera of hard coral at three stations in Bunaken Island. The data was collected using Line Intercept Transect (LIT) method which was dragged vertically at 3-15 meters depth. The results of study showed two different types of slopes, steep and gentle slopes. Stations 1 and 2 were categorized as steep slope (90° and 55°, respectively) and station 3 was gentle slope (43°). Encrusting growth forms dominated at 90° slope, while at 55° and 43° slope was dominated by massive growth forms. Vertical distribution of the corals shows change in size and numbers of colonies along with increasing depth.