The naked coral hypothesis: a cause for optimism?

There remains a cause for optimism. Shallow-water corals have weathered a host of insults over the last 18,000 years. The Atomic Age is just one in a long list. Since the Pleistocene Era, sea levels rose ~100m to the current sea stand. This literally drowned once thriving tropical reefs. You can scuba dive to 30m on Saba Bank, Caribbean Sea to a 1m high notch that indicates a wave swept shore, so long ago. Another 20m below, gorgonians grow on the dead coral heads of an ancient reef-crest. But who sheds a tear for the Pleistocene?

Corals are tougher than we give them credit for. They survived climate change before- perhaps in a different form, a polypoid form lacking calcite called “the naked coral” (Stanley and Fautin 2001).

Rugose corals thrived and developed during Paleozoic, but became extinct in the Permian. One of the primary hypotheses regarding the mass extinction of rugose corals is that increased levels of CO2 in the atmosphere resulted in reduced pH of seawater that altered the ability of corals to form their calcitic skeleton.

The threat of “ocean acidification” has also been invoked recently, but the phylogeny of corals has been largely overlooked. Laboratory research determined at least five species of corals can survive periods of low pH. They transform into a gelatinous mode akin to their conphyletic sea anemones, even maintaining their ability to reproduce and regrow skeletons as pH rises (Fine and Tchernov 2007). This supports the “naked coral” hypothesis.

The hypothesis has been used to explain the sudden reappearance of Scleractinian corals in the Middle Triassic, when ocean conditions returned to normal, after corals were absent from the fossil record for millions of years. They may have survived that time in a gelatinous state. its seems far fetched, but coral reefs have survived millions of years of sea level change. They’ve weathered hurricanes, monsoons, brine seeps, geological faults, and sedimentation from natural changes in riverine output and direction. They’ve been around a long time.

Modern corals are highly adapted. Some occur in shallow lagoons with daily temperature swings of 4 degrees C, more than the predicted average warming over your lifetime. The point is, we should take some solace from coral’s phylogeny. Corals are diverse, robust, and strong. So relax a little about global warming. It’s not all bad.

In my opinion, we need to pay more attention to wastewater and other types of near shore pollution. Impacts from bottom trawling and anchor damage must be controlled. We should focus on more pressing solutions to local problems, establish large protected areas, and work towards a greener future one shopping bag at a time. I can’t get worked up about climate change with all the other problems facing corals these days. That’s just the way I see it.

Reference:

Fine, M and D. Tchernov. 2007. Scleractinian Coral Species Survive and Recover from Decalcification. Science. v. 315, p. 1811.

Stanley, G.D., Jr. and D.G. Fautin. 2001. The Origin of Modern Corals. Science, v. 291, p. 1913-1914.