Last night we had a terrific talk in the beach house by Prof Phil Munday of the ARC Centre of Excellence for Coral Reef Studies and James Cook University: "Fish in hot water: how will climate change affect coral reef fishes?"

Coral reefs are already feeling the impacts of climate change, not only from increasing temperatures but also from the increasing acidity of seawater. Some of the carbon dioxide in the atmosphere is absorbed by seawater and as atmospheric levels rise, so too does the level in seawater and this causes the seawater to become more acidic. Any animal that builds a shell, including corals, finds it harder to do so in a more acidic environment - think of chalk dissolving in vinegar.

In his talk, Phil said that he has seen a sad decline in coral reefs in some parts of the world during the three decades that he has been involved in diving and research. In a process known as "phase shift", coral reefs can change from a community based on hard corals to one dominated by algae. This can be caused by many environmental insults including coral bleaching. Phil provided an interesting illustration (shown at right) "phase shift" from a personal viewpoint, noting that it happens quite quickly and is very hard to reverse!

It's not only the corals and other shell-building animals that are being impacted by climate change. Fish rely on the habitat that corals provide - take away the corals and you take away the habitat. Phil has found that two species of coral-dwelling goby have become locally extinct in PNG due to habitat loss.

Another of the really scary things his team has found is that larval fish change their behaviour when they're raised in water with elevated levels of carbon dioxide, as are predicted for later this century. Instead of avoiding the smell of predatory fishes, larvae are attracted to it. This is not a good plan for a young fish!

Phil, with students and colleagues, are at Lizard Island Research Station now, finding out more about how fishes are likely to respond to climate change.