Reef corals in a high sedimentation environment on the 'Mainland' coast of Brunei, Northwest Borneo

Abstract

The South China Sea coast of Brunei is located near the edge of the Sunda shelf with deep water offshore and very few islands, but numerous submerged bank reefs on the shelf. The inshore coastal waters of this part of northwest Borneo, like much of the shallow Sunda shelf waters of the rest of this large island, are affected by high river runoff and associated plumes of suspended parti­ culates. Consequently nearshore waters are characterized by soft sediments, an inshore turbid zone and very few natural reef coral formations. However, at the fringe of Brunei Bay, human intervention in the form of marine engineering works to create a channel access to Muara port has provided a rock bund substratum that, at one partly wave­sheltered location, has permitted the de­ velopment of a high cover of a wide range of hard coral colonies. These corals exist in a normal salinity environ­ ment (min. 30.3 ppt); apparently the rocky bund protects them from the direct influence of the estuarine plume that emanates from the harbour channel. However, this coral community has colonized, persisted and grown under a high sedimentation regime >70 mg cm day, a rate of sedimentation that is comparable to that reported else­ where for sediment­tolerant Scleractinia but which is considered high for Acropora species. This artificial coral community is of interest in the context of natural reef coral communities near estuaries and, additionally, this particular site has a potentially high bio­ monitoring value given present and planned land use changes in the hin­ terland of Brunei Bay.