| Summary: | The marine environment is facing the dual threats of rising temperature and ocean acidification. Coral reef ecosystems are thought to be especially sensitive to these threats due to evolving in a relatively stable thermal environment and the susceptibility of reef building corals to ocean acidification. For populations of marine organisms to persist under climate change conditions, they must be able to reproduce and produce offspring that will survive in the environment. This study examined the effects of ocean acidification and increasing temperature on reproduction in a coral reef fish, the cinnamon anemonefish (Amphiprion melanopus) and tested how parental effects influence the susceptibility of the offspring to these dual stressors. Ocean acidification is predicted to negatively affect reproduction of marine organisms, but few studies have tested this prediction in marine fishes. In Chapter 2, I determined the effect of ocean acidification on reproduction of A. melanopus by exposing adult breeding pairs to near-future CO₂ levels for a period of 9-months. A current-day control (~400μatm) and two CO₂ treatments (moderate (~600μatm) and high (~1000μatm)) were used based on CO₂ projections for the year 2100. Contrary to expectations, high CO₂ conditions stimulated reproduction. Pairs exposed to high CO₂ produced twice as many clutches, 60% more eggs and had 80% higher reproductive output compared with controls. Despite the increase in fecundity there were no changes in egg or hatchling size. This suggests, that for some species, increased CO₂ may not be as stressful as previously thought. Further, it suggests that a relatively small increase in CO₂ could potentially have stimulatory effects (a hormetic response) in reef fish. While no negative effects of increased reproductive effort were detected for either the adults or the offspring, it is possible that there could be effects in the longer-term that were not possible to investigate in this study. Increasing CO₂ is the main driver of rising temperature and ...
|
|---|