Bioerosion in massive porites at reef flat area of the south Java Sea

Abstract

Scleractinian coral as the main builder of the reef contributes to building a complex reef framework through produce growing aragonite in their skeleton. In shallow water area (reef flat) the reef constructional process will be equal with erosional one, can be caused by mechanical damage such as storm or water motion and biological way (bioerosion). This research focused on the biological agent that influence on bioerosion process on massive Porites. 3 types of bioerosion they were grazing, boring, and etching. We monitored 10 massive Porites coral that was abundant at Pantai Kondang Merak, where each coral colony was segmented into 12 parts and then photographed to record data grazing and boring in massive Porites coral, while for etching was observed using Scanning Electron Microscopy (SEM). The result showed the number of bioerosion from grazing was 581 and boring was 1,155. The etching process was dominated by cyanobacteria Planobola macrogata that live inside of coral skeleton. The grazing process caused by parrotfish and triggerfish, boring caused by polychaetes, bivalves, and sponge. Bioerosion process not only weakening reef structures but also increase habitat complexity of reef-associated biota and expand coral occupy in space with natural propagation.