Hidden gems: unveiling the environment and biodiversity of Hong Kong’s intertidal boulder fields

Chau Kei Wong¹, Adrian Wong¹, Tommy Hui¹

¹Lingnan University, China

Intertidal boulder fields have long been a testing ground of ecological theories and more recently a conservation target amidst rapid coastal development and urbanization. In Hong Kong, which supports a disproportionately rich marine biodiversity (5943 recorded species, 26% of China’s total) relative to its small sea area ( 1640 km2), coastlines are mostly rocky ( 60%) comprising, among bedrock habitats, boulder fields of various sizes. This habitat, however, has been largely neglected in previous biodiversity surveys despite supporting a distinct assemblage as compared to bedrock habitats. To fill this knowledge gap, a project has been conducted to map the baseline biodiversity of Hong Kong’s intertidal boulder fields and investigate the relationships between such biodiversity and various key physical conditions on the shore.

To achieve that, 18 boulder fields of different sizes, wave-exposure and hydrological regimes were selected, and their biodiversity and physical conditions were measured on and underneath boulders. Specifically, physical variables including temperature and humidity, boulder size, the frequency at which boulders are being moved, and volume underneath boulders were quantified to test how thermal/desiccation stress, proneness to disturbance, and habitat availability may drive biodiversity patterns in terms of richness, composition and structure. Although the project is now at its starting phase, patterns have emerged regarding the variations in physical conditions and species composition across sites. This relationship between the physical environment and biodiversity will allow us to better understand species distribution patterns on Hong Kong’s intertidal boulder fields and, ultimately, contribute towards the conservation of this previously neglected, but ecologically rich habitat.