Ocean acidification impairs the physiology of symbiotic phyllosoma larvae of the lobster Thenus australiensis and their ability to detect cues from jellyfish.

Ocean acidification (OA) can alter the behaviour and physiology of marine fauna and impair their ability to interact with other species, including those in symbiotic and predatory relationships. Phyllosoma larvae of lobsters are symbionts to many invertebrates and often ride and feed on jellyfish, however OA may threaten interactions between phyllosomas and jellyfish. Here, we tested whether OA predicted for surface mid-shelf waters of Great Barrier Reef, Australia, under ∆ pH = -0.1 (pH ~7.9) and ∆pH = -0.3 (pH ~7.7) relative to the present pH (~8.0) (P) impaired the survival, moulting, respiration, and metabolite profiles of phyllosoma larvae of the slipper lobster Thenus australiensis, and the ability of phyllosomas to detect chemical cues of fresh jellyfish tissue. We discovered that OA was detrimental to survival of phyllosomas with only 20% survival under ∆pH = -0.3 compared to 49.2% and 45.3% in the P and ∆pH = -0.1 treatments, respectively. The numbers of phyllosomas that moulted in the P and ∆pH = -0.1 treatments were 40% and 34% higher, respectively, than those in the ∆pH = -0.3 treatment. Respiration rates varied between pH treatments, but were not consistent through time. Respiration rates in the ∆pH = -0.3 and ∆pH = -0.1 treatments were initially 40% and 22% higher, respectively, than in the P treatment on Day 2 and then rates varied to become 26% lower (∆pH = -0.3) and 17% (∆pH = -0.1) higher towards the end of the experiment. Larvae were attracted to jellyfish tissue in treatments P and ∆pH = -0.1 but avoided jellyfish at ∆pH = -0.3. Moreover, OA conditions under ∆pH = -0.1 and ∆pH = -0.3 levels reduced the relative abundances of 22 of the 34 metabolites detected in phyllosomas via Nuclear Magnetic Resonance (NMR) spectroscopy. Our study demonstrates that the physiology and ability to detect jellyfish tissue by phyllosomas of the lobster T. australiensis may be impaired under ∆pH = -0.3 relative to the present conditions, with potential negative consequences for adult populations of this commercially important species.