Experiment 2: Field experiment
Abundance estimates: Over the course of 5 nights, medusae were
collected in known jellyfish ‘hotspots’ (Schlaefer et al. 2020)
between September andNovember for C. sivickisi and one night
for C. xaymacana. Sites were separated by tens to hundreds of
metres in shallow waters near Magnetic Island, North Queensland
(19.1359o S, 146.842o E) (Table
3). The medusae of C. sivickisi and C. xaymacana are
photopositive and were attracted to lights using ‘JellyCams’
(Schlaefer et al. 2020); in this way it was possible to
estimate the presence and abundance of jellyfishes. Each ‘JellyCam’
had an LED torch (2000 lumens) attached to weighted crates. The
devices were lowered at each of the sites in 2-5 m of water and left
for 30 min to attract cubomedusae for sampling. A snorkeler obtained
an estimate of jellyfish abundance within a depth of 3 m from the
surface and within a 2 m radius of the light over a course of 2
minutes.
b.) Water sampling: For C. fleckeri, water samples were taken
during daylight hours in the Australian summer (January) in Horseshoe
Bay, Magnetic Island, Queensland, from four sites separated by several
hundreds of meters (creek, boat ramp, inside the stinger net and
northeast side of the bay). Horseshoe Bay was chosen due to historical
data from Surf Life Saving Queensland (SLSQ) indicating that medusae
were commonly present in the bay during the summer months (Dec-Feb).
For C. sivickisi, C. xaymacana and C. barnesi , Nelly,
Geoffrey, Arthur and Florence Bays, Magnetic Island, were chosen for
sampling due to historical evidence for containing adult medusae in
the Austral spring/summer (September-January) (Schlaefer et al.2020). Water samples were taken using sterilised 2 L containers
collecting water within 0.5 m of the surface and within a 2 m radius
of the JCAM light. Samples were stored on ice and taken back to the
lab where they were pumped through either a 20 μm (C. fleckerisamples due to high turbidity of sample), or 5 μm (C. sivickisi,
C. xaymacana and C. barnesi ) nylon filter within 12 h of
collection. Once filtered, filters were removed using sterilised
forceps and placed into Longmire’s preservative solution (Renshawet al. 2015). All environmental samples were stored at 4oC.