The effects of ocean acidification and warming on the early life history stages of spawning corals Acropora sp.

ABSTRACT:

The ‘double trouble’ scenario of elevated ocean temperature and acidity is becoming of increasing interest in the field of climate change research. Interestingly, events early in the life history of corals, prior to the initiation of calcification, such as fertilization, embryogenesis, larval survival and settlement are not overly affected by high acidity. However the possible synergistic effects of temperature and acidity have not been widely explored. Here, we tested the effects ocean acidification in combination with elevated temperature on early life history stages of several spawning acroporids from the Great Barrier Reef. I have structured my thesis into 3 hypotheses: 1) the effects of ocean acidification on the early life history stages of spawning Acropora sp. 2) The effects of ocean acidification and warming on the early life history stages of spawning acroporids and 3) The early skeletogenesis of acroporid recruits under near future acidification and warming regimes. We found no consistent effects of acid on fertilization, development, survivorship, metamorphosis and post-settlement growth rates, either alone, or acting synergistically with corals. And elevated acidity and temperature has no significant effect on the growth of new spat. In addition, a careful appraisal of the literature indicates that effects of acid are only apparent on unhealthy individuals or at unrealistically high levels. We conclude that near future ocean acidification levels is not an immediate threat to the early life history stages of Great Barrier Reef corals in the foreseeable future.