Habitats and benthic biodiversity across a tropical estuarine-marine gradient in the eastern Kimberley region of Australia

Abstract Although the Kimberley coast situated in north-western Australia has been recognized as one of the world’s least human-impacted coastal areas, many knowledge gaps remain and the diversity and extent of marine life in the Kimberley nearshore habitats, north-west Australian remains. One region that has not been comprehensively surveyed is the King George River, far north-eastern Kimberley. Consequently, a multi-taxon biodiversity and habitat survey was conducted in 2014. The survey included 146 stations ranging from the base of the King George River twin waterfalls to the mouth of the river and 15 km offshore into the Timor Sea. The King George River region contains at least eleven habitat types. As the river bends some four and a half kilometres upstream from the mouth, there are extensive stands of mangroves. Rocky shores occur along the coast. Lesueur Islet is a low, vegetated islet surrounded by a fringing coral reef. Subtidally, the reef supports a diverse coral fauna and algal flora. Deep-water sedimentary and filter feeder communities occur offshore around and beyond Lesueur Islet. A total of 1374 animal and plant lots were collected, comprising about 3500 specimens. A total of 796 species were recorded. There were at least nine new species discovered of which five have since been named. The new species comprised five crustaceans and four echinoderms. In addition, there were eleven new records for Australia (one Cnidarian, two Echinoderms, multiple molluscs, eight crustaceans) and eighteen new records for Western Australia (all Crustaceans.) Our species accumulation curve analyses suggest true species richness may have been much higher than this and that we sampled a small area from a highly diverse community. Total richness is anticipated to be far higher. It is likely that the results are, in part, due to under sampling of hard bottom substrate in the region.