CO2, global warming threatening life in Earth’s oceans
June 11th, 2009New Scientist reports that over the last 40 years, the Caribbean’s spectacular branched corals have been flattened.
In the late 1970s, white-band disease swept through the reefs, killing 90 per cent of the most spectacular tree-like elkhorn and staghorn corals. In 1998, many of the remaining tree-like corals were wiped out during a massive bleaching event, probably driven by global warming. Fast-growing but short-lived “weedy” species of corals then took over the reefs, out-competing most of the remaining tree-like corals. “Flat” reefs now cover 75% of the Caribbean, compared to just 20% in the 1970s.
The intricate tree-like corals provide sanctuary for unique reef fish and other creatures and protect coastlines by sapping the energy of waves. At least they used to.
Acidification due to increased CO2 levels is also damaging corals and threatening life in Earth’s oceans. Corals and plankton, at the base of the marine food web, rely on sea water saturated with calcium carbonate to form their skeletons. As acidity intensifies, the saturation declines, making it harder for the animals to form their skeletal structures. Analysis of coral cores shows a steady drop in calcification over the last 20 years. Put more CO2 into the air above and it dissolves into the oceans.