Validation of eDNA as a viable method of detection for dangerous
Stings from certain species of cubozoan jellyfish are dangerous to
humans and their seasonal presence in tropical marine waters poses a
significant risk to coastal communities. The detection of cubozoans is
difficult due to high spatial and temporal variation in their occurrence
and abundance. Environmental DNA (eDNA) has the potential to detect rare
species and therefore offers potential to detect cubozoans, not only
pelagic medusae, but presence of cryptic polyp life-stages. The
objective of this study was to validate the use of eDNA as a viable
detection method for four cubozoan species (Chironex fleckeri, Copula
sivickisi, Carybdea xaymacana and Carukia barnesi). Species-specific
primers were developed for each of these four cubozoans and an eDNA
approach validated utilising both laboratory and field trials.
Laboratory DNA degradation experiments demonstrated that C. sivickisi
DNA degraded quickly but could still be detected in sea water for up to
9 days post-jellyfish removal. Positive detection was found for C.
fleckeri, C. xaymacana and C. sivickisi medusae in the waters
surrounding Magnetic Island, Queensland, in the Austral spring/summer
(September-January). Based on visual surveys there was a poor
relationship between concentration of eDNA and abundance of jellyfish.
Positive eDNA amplification was also shown near the substratum when C.
sivickisi medusae were absent. This can only be explained by the
detection of polyps. Consequently, eDNA is an effective tool to detect
both the medusae and polyps of cubozoans. This approach provides the
means to reduce the risk of envenomation to swimmers and enhance our
knowledge of cubozoan ecology.