Benthic ostracod diversity and biogeography in an urbanized seascape

Hong Kong is one of the most urbanized coastal cities in the world. Yet, despite extensive anthropogenic impacts, adjacent marine environments harbour tremendous biodiversity. We investigated how the diversity, taxonomic composition, and biogeography of meiobenthic ostracods in Hong Kong's coastal waters vary in response to natural and anthropogenic factors. Our regression models indicated that metal pollution and mud content were the main factors affecting meiofaunal diversity, with eutrophication also playing a role. The highest diversity was observed in the Victoria Harbour region at the center of Hong Kong's urbanized seascape, and the lowest diversities were observed in Mirs Bay, Port Shelter, and Tolo Harbour. Ostracod diversity and biogeography patterns are congruent with published studies of other soft-sediment fauna, which also identified a diversity peak in Hong Kong's urban center and a vast southern water biofacies characterized by muddy and turbid conditions. These results do not apply to organisms that prefer oligotrophic conditions, such as hard corals. For those taxa, eutrophic waters in western Hong Kong are generally not habitable and higher diversities are observed in less productive, eastern waters. Our findings indicate that meiofaunal ostracods can be used more broadly as a bioindicator for the diversity of soft sediment benthos.