MEPS 728:25-41 (2024)  -  DOI: https://doi.org/10.3354/meps14507

ABSTRACT: Considerable gaps in our understanding of cubozoan ecology exist due to challenges associated with their detection. Environmental DNA (eDNA) removes the need for physical identification, offering a new approach to detect and study these elusive taxa. The objective of this study was to utilise eDNA as an ecological tool to test hypotheses surrounding the ecology of the Australian box jellyfish Chironex fleckeri, through examining the presence of both polyp and medusa life history stages. Additionally, the utility of eDNA as a proxy of abundance was explored. This study was conducted within and outside of Port Musgrave, a semi-enclosed estuarine system in northern Australia. eDNA proved successful in detecting both life history stages. Polyps were detected during winter when medusae were absent. This detection allowed investigation into potential polyp habitat. Polyps were exclusively detected in habitats characterised by nearby patches of rocky substrata and shallow carbonate reefs, with no detection occurring in mangrove habitats. The highest frequency of medusa detections occurred within Port Musgrave, while detections outside were more sporadic. Through comparing the distributions of both life history stages, evidence suggests that Port Musgrave is likely a population stock of the species, aligning with predictions from biophysical models. Finally, use of eDNA as a proxy of abundance showed a poor relationship, which can be attributed to likely higher variance in eDNA concentrations resulting from the spatially dispersed nature of the jellyfish. We conclude that eDNA provides a new approach to study cubozoan ecology and will provide critical information needed to mitigate against their threat of envenomation.

KEY WORDS: Cubozoa · Box jellyfish · Environmental DNA · Detection · Life history · Polyps · Ecology · Population structure