An uncommon intertidal record of Halophila decipiens Ostenfeld in the vicinity of mangroves

Abstract

In this paper, we report the occurrence of Halophila decipiens Ostenfeld found growing in an intertidal environment. At the study site of Sungai Bahan estuary located along the Straits of Johor (Malaysia), the seagrass grew sparsely in the lower littoral zone of the mangrove coastline. Forming discontinuous patches, the seagrass was fully exposed on the mudflats during the lowest spring tides. Predictable times of exposure during low tides coincide with specific diel periods of lower light availability, which enabled avoidance of exposure to excessive irradiance. Hand-collected specimens of H. decipiens were initially defined through morphological and inflorescence characteristics. The identity of the species was confirmed based on analysis of the internal transcribed spacer sequence of its ribosomal DNA. Further analysis of this sequence demonstrated that among global populations, H. decipiens formed a sub-clade with populations from Malaysia and Australia. The colonisation by H. decipiens at the study site demonstrates its opportunistic acclimation to local environmental conditions. This discovery opens opportunities to further explore its ecology, as an instance of a less commonly studied seagrass within the region and to further investigate the unusual intertidal niche associated with the species.