Coral Adaptation and Epigenetics

By Rud Istvan

WUWT has posted several excellent articles by Jim Steele on how global warming alarmism uses corals as the poster child for warming and acidifying oceans, none of which is scientifically justified. A brief review follows, calling attention to a recently discovered additional adaptation mechanism not covered AFAIK by Jim Steele’s posts. The motivation for this post was triggered by a recent lunch with newish neighbor Charles the Moderator (CtM), and his sharing many wonderful underwater photographs of the coral reef he now dives frequently off Pompano Beach (same reef system as off Fort Lauderdale, just a few miles further north and more conveniently onshore). If any coral reef images appear in this post, CtM added them and gets the photocredits.

I have had a longstanding interest in corals, since have been recreationally diving coral reefs for several decades, including those off my Fort Lauderdale beach condo since 2000. Even took my dive uncertified teenagers to the US Virgin Islands, where we snorkeled the reefs at the Carambola resort on St. Croix, and did the Virgin Islands National Park snorkel trail at Buck Island. It is the only underwater ‘hiking’ trail in the entire US National Park system.

Corals are now known to have three, not two, evolutionary adaptation systems. This fact alone refutes any coral climate alarmism such as regularly coming out of Australia concerning the Great Barrier Reef.

The first adaptation mechanism is simply Darwinian evolution. Corals are ancient animals and very diverse. They have been around since the Cenozoic era. You would correctly surmise that as an animal group, corals have already survived a LOT of climate change. Corals are part of the Cnidara phylum, in the class Anthoza, comprising 5 orders of which four exist and one is extinct. There are over 2400 known coral species.

From a global warming alarm perspective, Darwinian evolution probably works too slowly for corals to adapt to ‘sudden’ anthropogenic global warming and associated ocean acidification. (For more on that overblown ocean alarm, CtM has a separate possible post on seawater chemistry and ocean pH biology, excerpted and adapted from essay Shell Games in my ebook Blowing Smoke.)

The second major coral adaptation mechanism is bleaching, which Jim Steele has previously explained in detail here. In sum, corals are filter feeders. All shallow water corals in the ocean photic zone have evolved a secondary food source provided by symbiont zooxanthellae, which are photosynthetic dinoflagellate algae of the genus Symbiodinum. These live within the coral polyp body, and photosynthesize food for themselves and the host polyp. In return, the polyp provides its symbionts with ‘fertilizer’ from its metabolic waste products. Symbionts provide the profusion of coral colors seen when diving live reefs. Coral polyps are translucent, so without symbionts appear white against their calcium carbonate exoskeletons, which we incorrectly think of as ‘coral’. Broad variation in zooxanthellae species means each is exquisitely adapted to local temperature and pH. If seawater conditions change, corals have evolved the ability to bleach. They expel their current symbionts (thus appearing ‘bleached’ white), and then wait for better ones to come along. That happens naturally since better adapted zooxanthellae differentially multiply in abundance.

This adaptation mechanism is biologically fast, less than a year. Coral alarmists argue that if the polyps do not repopulate symbionts within a few months, they can starve to death (typically about a year or a bit more depending on local seawater fertility). That is true. In which case the dead reef will be eventually be repopulated from new coral larvae after the annual spawning. As prophetically said in Jurassic Park, “Life finds a way.”

Since about 2015, a third coral adaptation mechanism has been shown, epigenetics. Recent references are too numerous to link here. Interested readers can find dozens of papers and articles by simply googling ‘coral epigenetics’. Jean-Baptiste LaMarck was correct after all! Environmentally adapted traits CAN be passed down the generations. Especially in corals, which not only reproduce sexually by spawning, but also asexually by budding that directly transfers epigenetics to progeny.

Technically, the ‘noncoding’ DNA around each gene’s DNA (we skip the intron/exon ‘gene’ complication) determines when and how often a gene is expressed in relation to its cell’s ‘environment’. That is how embryos develop. The main method for ‘permanently’ turning off genes no longer needed as an embryo develops is DNA methylation, discovered by embryologists.

The big newish epigenetics realization is that DNA methylation can also ‘evolve’ in response the external environment, altering patterns of gene expression without evolutionary changes to the genes themselves. This alters the phenotype but not the genotype.

There is also a second epigenetic mechanism not found in embryology but recently found in many organism’s environmental responses. Since a cell’s nucleus chromosomes have their DNA strands bunched up like a yarn tangle, the tangle has to unfold for interior genes to be expressed into RNA. RNA in turn is the template cellular cytoplasm machinery uses to make the protein the gene encodes. For conservation of ‘energy’, cells evolved DNA refolding where the most frequently used genes eventually get located on the DNA tangle’s outside.

Coral epigenetics has now been show to use both methods, and provides neither a very fast nor very slow adaptation response. It may take decades—just the right time frame to adapt to global warming and climate change.

Since I am leaving any coral images to CtM (and those would not show epigenetics anyway), illustrating how powerful epigenetic adaptation is uses an example more familiar to all, and verifiable in any grocery store, dried beans.

Modern genetic analysis of dried beans (all P. vulgaris) tells a fascinating epigenetics story. All the many domestic food phenotypes pictured above emerged near simultaneously from a single wild plant. As a result, they today still have very little genotypic variation amongst beans that superficially appear to come from different plants. Nope, all are P. vulgaris, no different than hundreds of dog breeds are all Canus lupus subspecies familiaris (translation, domesticated wolves).

Archeology shows that domesticated P. vulgaris emerged independently in Peru, (landrace kidney beans), in the Mexican highlands (landraces pinto and red beans), and once more in lowland MesoAmerica (landraces black and navy beans), all between 10000BCE and 8000BCE. These distinctly different bean phenotypes all emerged together during the emergence of sedentary agriculture and domesticated plants and animals. The DNA analysis proves bean phenotypes emerged through epigenetic selection rather than through genetic selective breeding—which would have introduced more genetic variation.

I agree with Jim Steele. Coral alarmism doesn’t amount to a hill of beans.