Ocean acidification does not affect the early life history development of a tropical marine fish

Determining which marine species are sensitive to elevated CO 2 and reduced pH, and which species tolerate these changes, is critical for predicting the impacts of ocean acidification on marine biodiversity and ecosystem function. Although adult fish are thought to be relatively tolerant to higher levels of environmental CO 2 , very little is known about the sensitivity of juvenile stages, which are usually much more vulnerable to environmental change. We tested the effects of elevated environmental CO 2 on the growth, survival, skeletal development and otolith (ear bone) calcification of a common coral reef fish, the spiny damselfish Acanthochromis polyacanthus. Newly hatched juveniles were reared for 3 wk at 4 different levels of P CO 2(seawater) spanning concentrations already experienced in near-reef waters (450 atm CO 2 ) to those predicted to occur over the next 50 to 100 yr in the IPCC A2 emission scenario (600, 725, 850 atm CO 2 ). Elevated P CO 2 had no effect on juvenile growth or survival. Similarly, there was no consistent variation in the size of 29 different skeletal elements that could be attributed to CO 2 treatments. Finally, otolith size, shape and symmetry (between left and right side of the body) were not affected by exposure to elevated P CO 2 , despite the fact that otoliths are composed of aragonite. This is the first comprehensive assessment of the likely effects of ocean acidification on the early life history development of a marine fish. Our results suggest that juvenile A. polyacanthus are tolerant of moderate increases in environmental CO 2 and that further acidification of the ocean will not, in isolation, have a significant effect on the early life history development of this species, and perhaps other tropical reef fishes