The nocturnal zonation of decapods in the subtidal zone within the reef seascape—abiotic factors defining habitats

The relationship between populations of marine organisms and physicochemical gradients directly influence distributions of species within associated seascapes. This study examines the impact that exposure to sunlight and substrate type has on the distribution of decapods in a tropical coastal reef environment. The study was performed at night when the species are at their most active using a visual census methodology to observe the natural nocturnal behaviour. The research revealed the existence of three distinct habitats housing specific decapod assemblages within tropical hard substrate environments; the External-Reef habitat which accommodates colonial benthic host decapods; the Crevicular-Reef habitat which accommodates the reef-stygofauna; and the Interface habitat between the reef and soft substrate which is habituated by transient decapod species. The findings extend the previous zonation patterns for decapods to the subtidal zone using physical parameters as the rationale defining allocation. The study collated and reviewed documented taxonomic and ecological evidence which supports this division of decapods into similar reef seascapes worldwide. It further proposes that this format of subtidal zonation may be applicable on a global scale to species which inhabit a comparable ecological niche within tropical zones.