Coral bleaching and ocean acidification

Global warming alarmists make much of how there are greater expanses of corals bleaching and the oceans are becoming more acidic. Besides the fact that man is not causing the Earth to warm by CO2 emissions, it could be that there is nothing to worry about in these two events. One is a survival mechanism and the other is self limiting. 

coral collage


Firstly, corals are meant to bleach. Corals get their colour from algae which live on them. Whenever there is a change in the local environment, one set of species of algae ups and leaves and a new set of species of algae which like the new environmental conditions soon takes its place. The period in between the different species of algae taking up residence is what makes the corals look white – coral bleaching.


This is a very strong adaptation mechanism and explains in part why corals have been around for so long even though the world climate has changed many times over the millennia.


Secondly, the oceans have become a little more acidic over the past few hundred or more years due to an increase in CO2 in the atmosphere. The ocean water absorbs a bit of the gases over the top of them. This is one of the ways that oxygen gets in the water so that fish can “breath”. If there is more or less of a certain gas in the air, more or less of that gas will be absorbed by the oceans.


However, there is a limit to how much of any gas can be absorbed by the oceans. When water is warmed, you can dissolve a greater concentration of solids in it. Try it with a cold glass of water and a warm glass of water and either sugar or salt.


The opposite happens with gases. When the water is cooler it can absorb more gas than when it is warmer. The reason for this opposite effect is due to the physical properties which make a substance a gas, a liquid or a solid – at a certain temperature. If the surrounding temperature drops hugely, CO2 will freeze into ice. At some temperature in between it will become a liquid. On the other hand even metal or rock will become liquid if you apply enough heat.


As you heat a liquid, it releases more of the gas that is absorbed in it. This explains why warm Coke or beer goes “flat”.


Therefore, there is a limit to how much CO2 can be absorbed in the oceans. It is possible that the oceans are at or close to the level of CO2 they can absorb at the current level of global temperature. If the Earth’s temperature rises a little more, it will be able to absorb less. Therefore the CO2 will stay in the atmosphere, rather than being dissolved in the water of the oceans.


This then means there will be a lid on the amount of acid that can be caused by CO2 being absorbed in the ocean water and reacting with other compounds and elements dissolved in the ocean water.


 The moral of the story – even if the world is warming by whatever mechanism, the coral reefs will adapt and the degree of ocean acidification will level out. That puts out the lights on two global warming alarms.

Slowing of Coral Growth in Great Barrier Reef

Today’s newspaper articles on a paper published in Science state that the scientists attribute the declining rate of growth of a particular type of coral to climate change and increasing acidity in the ocean due to greater absorption of CO2.

The abstract of the article Declining Coral Calcification on the Great Barrier Reef states:

The causes of the decline remain unknown; however, this study suggests that increasing temperature stress and a declining saturation state of seawater aragonite may be diminishing the ability of GBR corals to deposit calcium carbonate.

The scientists Glenn De’ath, Janice M. Lough, Katharina E. Fabricius of the Australian Institute of Marine Science report that their data suggests that the decrease in calcification of 14.2% since 1990 is unprecedented in the past 400 years.

Aragonite is CaCO3 – a form of calcium carbonate. It makes sense that this is important to coral growth. But what might be reducing the saturation of aragonite in seawater around the Great Barrier Reef? On further research I found that CO2 reacts with H2O and CaCO3 to make Ca and H2CO3 – carbonic acid! Aha – so that is why the oceans are becoming more acidic.

So what happened to corals much more than 400 years ago? The Earth was at least as warm, some say warmer, in the Medieval times. Coral was around then, so how did it cope? Maybe the answer is in slower growth, not killing. The coral is growing more slowly, but will recover again when the temperatures reduce with the next Little Ice Age. What is happening with coral in other locations around the world?

What will happen/ has happened to coral when the planet cools?

Coral seems to be pretty resilient. It has survived Crown of Thorns plagues, bleaching episodes and massive quantities of superphosphate washing out of Queensland rivers. I would like to see more studies of what has happened to corals over time with other unfavourable events.

As for the scientists claim that this is due to global warming from man-made CO2 (as at least one stated on camera), I didn’t see any reference to their proof that CO2 is increasing in the atmosphere due to man made causes, nor that this is causing global warming.

All that can be concluded is (possibly) that the rate of growth of one type of coral in the Great Barrier Reef has been slower recently than it has in the past.

Am I correct in understanding that the coral is STILL GROWING, just 14.2% more slowly?