Two scientific studies released today highlight the dangers of rising acid levels in the world's oceans.
Oceans play a vital role in climate change by absorbing carbon dioxide (CO2) and helping to reduce global warming, but CO2 makes ocean water more acidic.
Now a study published in the journal Nature Climate Change shows acidification will drive substantial changes in ocean ecosystems this century.
The authors assessed a range of marine animals including corals, starfish, molluscs, crustaceans and fish.
As acid is added to the oceans, there is less of the ion which many sea organisms use to make shells and which is used to make coral.
The authors found all groups were negatively affected by moderate ocean acidification, and conclude that ocean acidification is likely to profoundly alter ecosystems in the future.
Dr Will Howard, a visiting fellow at the Australian National University School of Earth Sciences, has also studied the effects of ocean acidification on marine animals.
"I think the picture is emerging that ocean acidification is likely to be detrimental to certain processes that are important to ecosystems," he told The World Today.
"A good example of which is the calcification process that corals and some other organisms undergo."
Dr Howard says that could lead to weaker shells and weaker coral.
"And that has important implications, both again for the functioning ecosystems, (as well as) if you consider the implications for small island nations that are ringed by coral reefs, the reefs also provide protection against storm surges and wave damage," he said.
"So in combination with rising sea level, these kind of impacts may put these reef ecosystems at risk of not being able to keep up as sea level rises in coming decades."
Positive feedback loop
In a second study, also published today in Nature Climate Change, scientists at the Max-Planck Institute for Meteorology in Germany say ocean acidification may amplify climate change.
They have found it causes a decrease in the production of a sulphur compound, dimethysulphide, which protects the atmosphere from solar radiation.
That study is and its authors say this positive feedback loop has not been identified before.
The authors estimate the effect of less dimethysulphide in the atmosphere could increase global warming by nearly 0.5 of a degree by the end of this century and say this should be considered in future climate change projections.
Dr Will Howard says some of the impacts of ocean acidification are already being felt in Australia.
"We can actually detect some of them in the marine environment," he said.
"The implications for Australia are that some of the ecosystems that we are mainly concerned with, like reefs such as Ningaloo and the Great Barrier Reef.
"But also temperate reef environments which are very important habitats for many of our important fisheries similarly might be at risk from ocean acidification in combination with other impacts."