When you think about the impact of climate change on the reef, you probably think about coral bleaching. Few people have heard about ocean acidification, but for many marine scientists this is an even more worrying issue… just harder to explain because you can’t see the impacts as easily as you can see bleached coral.
However, Acid Test, a new documentary starring Sigourney Weaver, produced by the National Resources Defence Council (NRDC) explains ocean acidification in terms we can all understand.
You’ve probably heard about how the ocean absorbs carbon dioxide (CO²)? Well, this comes at a cost - ocean acidification. As CO² is absorbed by the ocean, it increases the acidity of the water (lowering the pH value). Ocean pH has been relatively stable for 20 million years, but has risen dramatically (30%) in the last 250 years. This increasing acidity reduces the amount of carbonate atoms in the water which marine animals likes corals, shells, crustaceans and zooplankton need to absorb to create their protective external skeletons (made of calcium carbonate, or limestone).
This means that e.g. corals grow more slowly, and the skeletons of many animals are thinner and more fragile (effectively the marine equivalent of osteoporosis), providing them with less protection. Ever visited a limestone cave? Then you’ll have witnessed how the acidity of rainwater gradually dissolves limestone. Scientists believe that the “tipping point” for reefs – when the rate of erosion begins to outstrip growth – could be as soon as 2050… within many of our lifetimes.
This will have global implications for marine ecosystems and for the millions of people that rely on coral reefs (and marine life in general) for income (from tourism and fishing), coastal protection (healthy reefs offer coastlines protection from storm surges and tsunamis) and protein – not just the crabs and lobsters we enjoy in fancy restaurants but for the 350 million people in developing countries who depend on coral reefs to provide their only source of protein. Ocean acidification not only threatens to disrupt the marine food web, but to bring hardship to millions of people around the world.
To learn more about ocean acidification and its potential impact, look at:
- Ocean Acidification: The Other CO²Problem pages on the NRDC website
- or download the NRDC factsheet in PDF format
- watch the Acid Test documentary.
