The Coral Endures – Watts Up With That?

Guest Post by Willis Eschenbach

I keep reading endless hype about the Great Barrier Reef (GBR) getting bleached out of existence. So let’s start with some facts.

First, coral is not a single organism. Coral is a curious critter. Coral is a symbiotic partnership between an animal from the Anthozoa group and a microbial alga called Symbiodinium. The microbial algae use photosynthesis to create sugar, and the Anthozoa polyps feed off the sugar. Here’s a description from the USGS.

Figure 1. Description from the USGS article: “The hard skeleton of coral is formed by the secretion of calcium carbonate by the polyp. The cup-like skeleton deposited by an individual polyp is called a corallite. Polyps gather food particles with the nematocysts (stinging, venomous cells) in their tentacles, and feed from sugars produced by photosynthesizing zooxanthellae, a type of algae. The coral tissue protects these algae from herbivorous grazers, and the algae in turn use many of the polyps’ waste products such as carbon dioxide, nitrogen, and phosphorus. Illustration by Laura Torresan, USGS“

Next, modern-type warm-water shallow coral reefs have been around for about half a billion years … so obviously, they must be resistant to temperature changes, including the large temperature swings in the transitions between the glacial periods and the interglacial times such as the current Holocene.

Next, “bleaching”. Bleaching is the natural response of coral to excessively warm or excessively cool temperatures. Or to pollution. Or to siltation. Or to toxic chemicals. Or to the death of the parrotfish or other grazers that keep the coral from being overgrown by other plants.

When the symbiotic relationship comes under pressure due to any of those stressors, the algae may leave the coral’s tissue. And if the stress is due to pollution, siltation, or the lack of parrotfish, then the reef may die.

But if the bleaching is from unusual temperatures, the reef doesn’t usually die. Instead, something entirely different happens. The usual outcome of bleaching due to temperature change is that after the algae die and are expelled by the coral, a different strain of algae that is adapted to the new temperature takes up residence in the bleached coral skeleton.

It’s easy for the new algae to colonize the coral—at that point the coral is like an apartment house where the tenants have all moved out. The new algae can colonize the coral without having to build up the structure. So the reef usually comes back to full health quite quickly.

How do I know this stuff? Hours and hours of scuba and snorkel diving on coral reefs, plus four years living on a coral atoll. I’ve seen the bleaching and watched the reef recover.

Now, as I mentioned at the top of the post, there’s all kinds of hype about what might happen to the GBR, or to the reefs off of Florida and the Keys for that matter, if the ocean warms up and doesn’t cool back down.

However, what most folks don’t know is that a) coral reefs like warm water, the warmer the better, and b) the GBR and the Florida reefs are at the coldest end of the temperatures where shallow-water corals reefs can grow. (And yes, I know there are deep cold-water corals … but we’re not talking about those, are we?)

So let’s start with the location of the GBR. It’s on the northeast coast of Australia, shown in the map below.

Figure 2. Location of the Great Barrier Reef

And where is that in relation to the rest of the world’s coral reefs? Well, very few coral reefs exist where the year-round water temperature is less than 23°C (73°F). And here’s a map of that region.

Figure 3. Temperature range where corals thrive (colored areas), and the area where most corals live (red box).

So … as you can see, both the Florida reefs and the GBR are in the coldest part of the temperature range where corals are happy. And most coral reefs are in the warmest ocean waters. So we know that there are plenty of warmer-water-adapted algae and warmer-water coral reefs.

And of course, this means that if the ocean in those areas of the GBR and Florida reefs gets and stays warmer … all that will happen is that some reefs will bleach, warmer-water-adapted algae will recolonize the reefs, and finally, because of the warmer waters, the reefs will be able to expand polewards.

A final note. Almost nowhere is the open ocean’s annual average temperature warmer than ~30°C. And as the ocean’s temperature overall has warmed, the warmest waters have stayed the same temperature. So a warming ocean is no threat to corals growing in the warmest ocean waters.

TL;DR version? While humans threaten coral reefs via pollution, pesticides, and siltation, corals like warm water. They are happiest where the water is warmest. Corals have survived radical changes in the temperature of oceans over geological time. Bleaching is the natural way that corals adapt to changing water temperatures.

And as a result … all of the hype about the corals and “global warming” is just another part of the climate alarmism scam. They’re not under any kind of threat from warming oceans. Or to misquote Mark Twain, “The rumors of coral’s death are greatly exaggerated”.

w.

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