Unlocking Hong Kong’s hidden jellyfish diversity with citizen science

Abstract

Jellyfish are important organisms within marine ecosystems, although the extent of their occurrence and diversity is likely underestimated, particularly for biodiversity-rich locations such as the Indo-Pacific. The potential for citizen science to monitor phenomena associated with these Cnidarians over large spatial scales has been recognized in an increasingly broad array of locations, including the Mediterranean, South Africa, and the UK. Here, we were interested if such an approach could be used to understand more about their presence, seasonal occurrence, and distribution in Hong Kong. To address these areas, the Hong Kong Jellyfish Project was launched in early 2021 with citizen scientists invited to submit photographs and simple information (date, time, location, number of jellyfish) to a project website or a collection project on the online citizen science biodiversity platform iNaturalist. For some of these observations, jellyfish were sampled and DNA analysis conducted to confirm morphologically-based identification. During 2021, over 380 observations of jellyfish were submitted through the website and iNaturalist project, with 19 species recorded as present. The species most frequently recorded were Cyanea nozakii and Rhopilema hispidum, and two new species records of Thysanostoma loriferum and Netrostoma setouchianum were documented for Hong Kong. There was a seasonal trend in observations, with most jellyfish seen in March–May. Finally, there was a broad geographical distribution of observations throughout Hong Kong’s coastal waters, with more observations made in the south/east. Together, these observations gathered by citizen scientists indicate a broad distribution of jellyfish – and the occurrence of previously undocumented species – in Hong Kong’s waters.