Ocean acidification happens as the oceans absorb excess CO2 in the atmosphere, causing the pH of seawater to fall. This has wide-ranging consequences for the marine ecosystem, among which are coral bleaching and preventing the shellfish shells from forming properly.
Jason Hall-Spencer’s groundbreaking SOSF-funded research on ocean acidification involves studying sites with naturally high levels of CO2, such as those near underwater volcanic vents off Italy. He recently discussed some of his findings and the implications of rising CO2 levels for the Mediterranean in C&EN magazine:
A fall in Mediterranean pH has major impacts on organisms that use calcium carbonate in their shells or corals. That’s because acidification—due to dissolved CO2 forming carbonic acid—throws normal ocean chemistry out of balance, resulting in corrosion of calcium carbonate from shelled organisms. In practice, this means that an organ￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼ism’s shell will dissolve unless the organism can ramp up shell construction to counteract the loss. “If the organism is willing to put a huge amount of energy into shell production because it has tons and tons of food, then perhaps the organism can continue to exist.”
Hall-Spencer focuses on underwater volcanic vents around Italy and Greece because these are areas where high acidity occurs naturally, allowing scientists a glimpse at what may be in store for future oceans. And the picture is not rosy:
When he swims through a Jacuzzi of CO2-rich water near vents to do experiments, Hall-Spencer says he regularly gets stung by invasive species and jellyfish, which thrive in that environment. “But the corals that we transplant into the areas dissolve away,” he says. “So corals die, but invasive species survive.”
However, he also points out that certain robust species are capable of adapting to more acidic environments:
Not all endemic species die in acidified oceans, however. “What keeps me from crying into my cornflakes in the morning is the fact there are some organisms that are clearly very robust,” Hall-Spencer says. “Some of them can survive what we are doing to the chemistry of the oceans. Sea grasses, for example, which can provide nursery areas for juvenile fish, bloom in [acidified] regions around Mediterranean CO2 vents.”
The full article is available here as a PDF download.