Coral Bleaching

The planet is starting to heat up, and the ocean is getting warmer. There is no denying it.

There is a chance that putting 40 billion tons of pollution in the air per year in the form of the greenhouse gas carbon dioxide may be part of the problem. To help you visualize this quantity just imagine the weight of 400,000 aircraft carriers as an odorless gas. At this time it is the view of 97% of climate scientists that this is the case.

On the other side there are those making a political argument (which is never self-serving). They tend to agree that there is warming, although their belief is that the process is natural, and not related to mankind's industrial, and recreational activities.

Because I am just naturally one of those committed to bringing people of different dogmas together, let me put forth this hypothesis; Of course the warming is natural. We are natural, we occur naturally on this planet, our activities are natural, our consumption is natural, and so we produce waste, which is natural.

Reproduction is natural, and growth is natural. The fact that there are close to three times as many people on this planet as when I was born is natural (2.76 billion then, 7.56 billion now), and that the consumption and the production of waste is in excess of three times what it was, is natural.

So, by extrapolation these increases are natural.

Pillar Coral Bleaching - November 2017

Photo – Mickey Charteris

Of course, they still increase, naturally.

As the over-all temperature rises, the ocean gradually gets warmer, and we are starting to witness some effects. Even slight increases in temperature, the type that might make you consider taking off your sweater, are enough to affect the coral here on the Caribbean reefs, and we get a phenomenon called Coral Bleaching.

The different colors found in most hard, reef building corals is actually a photosynthetic algae called zooxanthellae (which never seems to  be capitalized). The coral and the algae are in a mutualistic relationship with the coral providing a protective environment along with some required nutrients for the photosynthesizing. The algae through the photosynthesis provides oxygen and removes wastes, along with producing glucose, glycerol, and amino acids which the coral uses to make proteins fats, carbohydrates, and the all  important calcium carbonate.

The relationship between the algae and coral polyp makes possible a tight recycling of nutrients, in nutrient-poor tropical waters. In fact, as much as 90 percent of the organic material photosynthetically produced by the zooxanthellae is transferred to the host coral tissue, and is its main food source.

Agaricia bleaching with algae - September 2016

Photo – Mickey Charteris

The coral bleaching is caused by stress of the colony whether from pollution or temperature increase, when the coral throws off the algae cells, and takes on a stark glaring white appearance. Should the coral go too long without the nutrient providing algae, it will die. However should the temperature drop to acceptable levels, or the pollution subside, in a short time the coral can recover, as seems to be the case this year, here in the western Caribbean. However Australia is reeling from a horrific bleaching event purported to have killed 22% of the Great Barrier reef.

We are near the end of the third bleaching event recorded here in the Caribbean (February 2017), and the reef is recovering as the temperatures fall. There was a strong warming trend that caused much bleaching in 2005, another lesser event in 2010, and this year's bleaching. At this time the bleachings have co-incided with the el Nino climate anomaly, but the expectation is that with overall increasing temperatures we will be seeing more bleaching in the all too near future.

Here on Roatan the most bleaching was seen on  the Whitestar Sheet Coral (Agaricia lamarcki), a fairly common species in these parts, found at depths of 70 to 120 ft. This summer after spending just a month out of the water, it was shocking to swim to the edge of the reef and see the white patches spread out below.

The series below shows advancing of the Coral Bleaching over the summer, and thankfully the recovery this winter.

Disclaimer: The author of this post is the graduate of a failed secondary education experiment, and has had no schooling in any science put forth in this blog. Quote it at your own peril.