Will jumping snails prevail? Influence of near-future CO2, temperature and hypoxia on respiratory performance in the tropical conch Gibberulus gibberulus gibbosus

Tropical coral reef organisms are predicted to be especially sensitive to ocean warming because many already live close to their upper thermal limit, and the expected rise in ocean CO2 is proposed to further reduce thermal tolerance. Little, however, is known about the thermal sensitivity of a diverse and abundant group of reef animals, the gastropods. The humpbacked conch (Gibberulus gibberulus gibbosus), inhabiting subtidal zones of the Great Barrier Reef, was chosen as a model because vigorous jumping, causing increased oxygen uptake ((M) over dot O-2), can be induced by exposure to odour from a predatory cone snail (Conus marmoreus). We investigated the effect of present-day ambient (417-454 mu atm) and projected-future (955-987 mu atm) PCO2 on resting ((M) over dot O-2,(rest)) and maximum ((M) over dot O-2,(max)) ((M) over dot O-2,O- (rest)), as well as MO2 during hypoxia and critical oxygen tension (PO2, crit), in snails kept at present-day ambient (28 degrees C) or projected-future temperature (33 degrees C). ((M) over dot O-2,O-rest), rest and ((M) over dot O-2,O-max), were measured both at the acclimation temperature and during an acute 5 degrees C increase. Jumping caused a 4-to 6-fold increase in ((M) over dot O-2), and ((M) over dot O-2,(max)) increased with temperature so that absolute aerobic scope was maintained even at 38 degrees C, although factorial scope was reduced. The humpbacked conch has a high hypoxia tolerance with a PO2, crit of 2.5 kPa at 28 degrees C and 3.5 kPa at 33 degrees C. There was no effect of elevated CO2 on respiratory performance at any temperature. Long-term temperature records and our field measurements suggest that habitat temperature rarely exceeds 32.6 degrees C during the summer, indicating that these snails have aerobic capacity in excess of current and future needs.