Ecology and Biodiversity of Rocky Intertidal Barnacles Along a Latitudinal Gradient; Japan, Taiwan and Hong Kong

The life cycle of barnacles is composed of a planktonic larval and a sessile adult stage. As a result the geographical distribution of barnacles is influenced by a combination of ocean currents, settlement success and subsequent recruitments. Barnacles show different geographical distributions along the, latitudinal gradient that connects the North West Pacific and South China Sea. On the Pacific coast of Honshu Japan the high shore was dominated by Chthamalus challengeri (>70 % cover). South of Honshu in Okinawa the high tide zone was populated by Nesochthamalus intertextus and Hexechamaesipho pilsbryi. In Taiwan the high tide zone was colonized by H. pilsbryi, Chthamalus malayensis and C. moro. In Hong Kong the high tide zone was occupied by C. malayensis (>60 % cover). The mid shores were all occupied by the genus Tetraclita. In the NW Pacific (Honshu, Okinawa and Taiwan), the common species were Tetraclita kuroshioensis, T. japonica japonica and T. j. formosana. In Hong Kong, only T. squamosa and T. j. japonica were recorded. The life history pattern of the barnacles in Hong Kong was seen to follow a seasonal trend not observed in the NW Pacific, in the warmer waters of Hong Kong early gonad development and settlement were followed by a regular summer die-off linked to heat and desiccation stress. Barnacles in Japan were found to have a shorter reproductive period and a longer life span than those in Hong Kong. Association with different ocean currents explains some of the difference in barnacle composition between Hong Kong and the NW Pacific, the rest is explained by the environmental and climatic changes along the latitudinal gradient and the ensuing differences of ecology and biodiversity found among the sites