Natural and Artificial Rocky Shores of Brunei, Including a Preliminary Checklist of Invertebrate Species

Abstract

This review summarises current knowledge of Brunei Darussalam’s rocky shore ecosystems. Although wave-washed rocky shores comprise a small fraction of the local coastal habitats, which are dominated by sandy beaches, mangroves, and mudflats, they support distinct and diverse faunal communities. We describe the formation, physical environment and biotic zonation of both natural and artificial rocky shores and compare the factors driving habitat heterogeneity for each shore. We also outline the known species diversity and the human impact on these shores. Two hundred and ten (210) invertebrate species are reported to occur on these shores, with intertidal gastropods (61 species) and subtidal cnidarians (45 species) being the best represented. Other typically diverse taxa, including sponges, crustaceans (decapods and amphipods) and polychaetes, however, remain poorly documented. The natural shores are continuously being disturbed and degraded by human activity, threatening local species extinction and reducing resilience and population recovery potential. This pressure is somewhat offset by the recent establishment of artificial rocky shores, which enhance the subtidal habitat and present novel intertidal habitat with respect to wave action exposure, especially the sheltering of rocky shores in modified embayment systems. Ecologically, artificial structures should facilitate greater colonization and recolonization potential by enhancing habitat and local larval supply. However, these structures present a small subset of the habitat types found on natural shores. Importantly, the artificial shores lack low-sloped or horizontal surfaces that trap waterbodies (tidal pools) during emersion and microhabitat/substratum complexity, both of which drive habitat heterogeneity and species diversity. We therefore call for further coastal research as a priority, to support effective conservation management of the remaining natural shores and to improve understanding of the ecological functions of artificial shores. Because of their limited extent, these ecosystems have been overlooked in the past, and this undermines Brunei’s responsibility for biodiversity conservation and its commitments within its national jurisdiction under international treaties.