Guest post by Willis Eschenbach
I've been reading endless hype about the Great Barrier Reef (GBR) disappearing due to bleaching. Let's start with some facts.
First, corals are not single organisms. Corals are curious creatures. Corals are symbiotic partnerships between anthozoans and microbial algae called Symbiodinium. Microbial algae use photosynthesis to produce sugar, which coral polyps feed on. Here's how the U.S. Geological Survey describes it.
figure 1. Description of the USGS article: “The hard skeleton of corals is formed by the secretion of calcium carbonate by coral polyps. The cup-shaped skeleton deposited by a single polyp is called a corallite. The polyp collects food particles with nematocysts (spiny poisonous cells) in its tentacles and encapsulates them in the form of zooxanthellae. Coral tissue protects these algae from herbivorous herbivores by feeding on sugars produced by photosynthesis of algae, which in turn utilize the polyps' many waste products, such as carbon dioxide, nitrogen, and phosphorus. Illustration by Drawing by Laura Torresan, USGS“
Next, modern types of warm water shallow coral reefs have been around for about 500 million years…so obviously they must be able to withstand temperature changes, including large temperature swings during the transition between glacial and interglacial periods, such as what is now the Holocene.
Next is “bleaching”. Bleaching is a natural response of corals to excessively high or low temperatures. Or pollution. Or siltation. or toxic chemicals. Or lead to the death of parrotfish or other herbivores that prevent the coral from being overgrown by other plants.
When the symbiotic relationship is stressed by any of these stressors, algae may leave the coral's tissue. If the stress is caused by pollution, siltation, or a lack of parrotfish, the reef may die.
But if bleaching is caused by abnormal temperatures, coral reefs usually don't die. Instead, something completely different happened. The usual result of bleaching due to temperature changes is that the algae die and are expelled from the coral. A different algae adapted to the new temperatures colonizes the bleached coral skeleton.
It’s easy for new algae to colonize the coral—then the coral is like an apartment building and the tenants have moved out. New algae can colonize corals without building coral structures. so Coral reefs usually recover to full health quickly.
How do I know these things? Hours of scuba diving and snorkeling on the reef, plus four years of living on a coral atoll. I’ve seen bleaching and I’ve seen coral reefs recover.
Now, as I mentioned at the top of the post, there's all kinds of hype going down about what might happen to the Great Barrier Reef or the reefs off Florida and the Keys if the ocean warms and doesn't cool down.
However, what most people don’t know is that a) coral reefs like warm water, the warmer the better, and b) the Great Barrier Reef and Florida Reefs are at the coldest temperatures that shallow water coral reefs can grow. (Yes, I know there are deep cold water corals…but that's not what we're talking about, are we?)
Let's start with the location of GBR. It is located on the northeast coast of Australia, as shown in the picture below.
Figure 2. Location of the Great Barrier Reef
Where does it stand compared to other coral reefs around the world? Well, there are very few coral reefs with year-round water temperatures below 23°C (73°F). Here is a map of the area.
Figure 3. The temperature ranges where corals thrive (colored areas) and the areas where most corals live (red boxes).
So…as you can see, both the Florida Reef and the Great Barrier Reef are in the coldest part of the temperature range where corals grow well. Most coral reefs are found in the warmest waters. So we know there's a lot of algae that's adapted to warm waters and warm-water coral reefs.
What this means, of course, is that if the ocean warms and stays warm in the Great Barrier Reef and Florida Reef areas… all that happens is that some of the reefs will bleach, algae that have adapted to the warmer water temperatures will repopulate the reefs, and ultimately, because in In warmer waters, coral reefs will be able to expand poleward.
the last point. There are almost no places where the average annual temperature of the high seas is higher than about 30°C. As ocean temperatures warm overall, the warmest waters stay the same temperature. Ocean warming therefore poses no threat to corals that grow in the warmest waters.
TL;DR version? Although humans threaten coral reefs through pollution, pesticides and siltation, corals prefer warm water. They are happiest where the water is warmest. Corals have survived dramatic changes in ocean temperatures over geological time. Bleaching is a natural way for corals to adapt to changes in water temperature.
Turns out…all the hype about corals and “global warming” is just another part of the climate alarmist scam. They are not under any threat from ocean warming. Or misquote Mark Twain, “Rumors of coral death are greatly exaggerated.”
w.
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