2011-01-04 08:57:26Intermediate Rebuttal No.148 - Coral are resilient to bleaching
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.205.130

CORAL - LIFE'S A BLEACH....... AND THEN YOU DIE

Despite what you may read or see in the mainstream media, out in the real world, massive and rapid changes are taking place in many ecological systems as a result of global warming. The Earth seems to be already convinced of global warming and is responding quickly.

Perhaps the most signicant, and likely most enduring, are the shifts taking place in the Earth's oceans. Whilst many readers may have read or heard about Ocean Acidification, there are numerous other changes taking place in the oceans which should be equally as concerning. One such phenomena to appear in the last few decades is mass coral bleaching, a consequence of the continued warming of the oceans. Once vast stretches of colourful reefs teeming with marine life are being reduced to lifeless rubble covered in seaweed or slime. Many areas are not recovering, and the scale and frequency of bleaching worldwide is getting worse. In fact, early reports suggest 2010 may have witnessed the largest single bleaching event ever recorded.

THE LOWDOWN ON CORAL BLEACHING

Reef-coral are actually a symbiosis (a mutually beneficial relationship) between the coral polyp, an anemone-like creature, and tiny algae called zooxanthellae. The coral provide shelter and nutrients for the algae , and in exchange the algae provide carbohydrates (food) to the polyp, using energy from the sun (photosynthesis) and the nutrients provided by the coral. These algae live in the skin tissue of the polyp and produce the coloured pigments which make coral reefs so visually spectacular. When this partnership breaks down the polyps expel the algae, which leads to the "bleached" effect. Although the polyp does feed using its tentacles to snare food, the bulk of its nutrition (90%+) comes from the algae, and they are a critical component of coral skeleton formation and therefore reef maintenance and growth. Without symbiotic algae, the coral can die from starvation, or become so weakened by a lack of food, that it succumbs to harmful bacteria (Mao-Jones 2010), and/or seaweeds which can poison and kill coral on contact.

Because reef-coral have adapted tolerance to a narrow band of envronmental conditions, bleaching can occur for a number of reasons, such as ocean acidification, pollution, excess nutrients from run-off, high UV radiation levels, exposure at extremely low tides and cooling or warming of the waters in which the coral reside. Typically these events are very localized in scale and if bleaching is mild, the coral can survive long enough to re-acquire new algal partners. So bleaching in itself is not something new, but mass coral bleaching on the huge scale being observed certainly appears to be, and represents a whole new level of coral reef decline.

OCEAN WARMING IS DRIVING MASS CORAL BLEACHING

As coral reefs operate very near to their upper limit of heat tolerance (Glynn & D'Croz 1990), bleaching en masse happens when the surface waters get too warm above their normal summer temperature, and are sustained at this warmer level for too long. The intensity of bleaching corresponds with how high, and how long temperatures are elevated and, as one might expect, the intensity of bleaching affects the rate of survival. Small rises of 1 -2 degree C, for weeks at a time, usually induce bleaching.

This episodic ocean warming has been most pronounced worldwide during El-Nino events, when the Pacific Ocean exchanges heat to the atmosphere and surface waters. In recent years though, severe mass bleaching is happening outside of El-Nino because of the "background" ocean warming. The huge mass bleaching in the Caribbean in 2005, a non El-Nino year, and again this year is a prime example of this (Eakin 2010) . Evidence connecting warm surface waters and mass coral bleaching has strengthened to the extent that the National Oceanic and Atmospheric Administration (NOAA) has a coral bleaching alert system in place. This alert system accurately forecasts mass coral bleaching based on satellite data of sea surface temperatures.

HOT WATER + CORAL = DEAD CORAL

So how does hot water kill coral?. It requires both high water temperatures and sunlight. Oxygen is released as waste during photosynthesis and like all chemical processes this is affected by temperature, speeding up as more energy (warmth) is applied. When water temperatures rise too high the protective mechanisms to prevent heat damage, employed by the coral and the algae, are overwhelmed. The zooxanthellae algae produce high levels of oxygen waste which begin to poison the coral polyp. In acts of self-preservation the coral kick out the algae, and in doing so become susceptible to starvation, opportunistic diseases, competitive seaweeds and macroalgae (slime to you and me) . Coral can succumb to the effects of bleaching years later, and for those coral that survive, growth effectively ceases and full recovery can take anything up to a decade.

CORAL RESILIENCE IS FUTILE

On a world scale coral reefs are in decline, and it makes for rather depressing reading for an avid diver like myself. Over the last 30-40 years 80% of coral in the Caribbean have been destroyed (Gardner 2003) and 50% in Indonesia and the Pacific (Bruno & Selig 2007). Bleaching associated with the 1982 -1983 El-Nino killed over 95% of coral in the Galapagos Islands (Glynn 1990), and the 1997-1998 El-Nino alone wiped out 16% of all coral on the planet. Globally about 1% of coral is dying out each year. Not all of this continual decline is solely down to bleaching of course, pollution and other human activities are also contributing, but bleaching is speeding up the loss of coral.

 

Looking only at bleaching though, we find that the incidence of mass coral bleaching increases dramatically in the last few decades. Despite modern records being biased by better monitoring and reporting in recent times, there seem to be little evidence of mass coral bleaching further back in time when examining long-lived coral communities. Studies from around the world show no signs of bleaching dating back many thousands of years, until recent decades (Abram 2003), (Aronson 2003). In the Caribbean there are no signs of previous mass bleaching dating back 220,000 years (Pandolfini & Jackson 2006)

So where does this resilience claim originate you may ask?. Perhaps from studies that have shown some coral, in secondary bleaching events, have lower rates of death. A few coral are in more fact tolerant to bleaching, some algae for instance manufacture their own "organic sunscreen". However this a only small proportion, major reef-building coral species seem incapable of forming long-lasting partnerships with these heat tolerant algae (Coffroth 2010), and the coral polyp themselves have a very poor genetic ability to adapt to warming (Csaszar 2010). However the "resilience" fallacy arose, there's no evidence a few hardy individuals will somehow prevent the loss of most coral worldwide.

THE IMPORTANCE OF CORAL REEFS - THE OASIS IN A MARINE DESERT

So what does this all have to do with the average man or woman in the street?, well, as far as humans are concerned, there is a rather large dollar value attached to coral reefs. Goods and services derived from coral reefs are very roughly estimated to be between $172 to $375 billion dollars per year (Martinez 2007). Not only that, but reefs directly provide food and income to over half a billion people worldwide. The decline of coral reefs is going to not only impact those that directly depend on them for a living and sustenance, but eventually have dramatic effects on economies worldwide, and will likely drastically drive up world food prices as fish populations nosedive.

Ecologically speaking the value of coral reefs is even greater because they are integral to the well being of the oceans as we know them. It might serve to picture them as the undersea equivalent of rainforest trees. Tropical waters are naturally low in nutrients because the warm water limits nutrients essential for life from welling up from the deep, which is why they are sometimes called a "marine desert". Through the photosynthesis carried out by their algae, coral serve as a vital input of food into the tropical/sub-tropical marine food-chain, and assist in recycling the nutrients too. The reefs provide home and shelter to over 25% of fish in the ocean and up to two million marine species. They are also a nursery for the juvenile forms of many marine creatures .

I could go on, but the similarity with the rainforest should now be clear. Eliminate the undersea "trees", which mass coral bleaching is in the process of doing, and you'll eliminate everything that depends on it for survival, a point best exemplified in the following sequence of photos. (sequence of healthy coral-bleached coral-rubble & slime)

A GRIM OUTLOOK FOR CORAL

The critical issue with global warming induced coral bleaching, as it is for many eco-systems, is the speed of warming. They are simply not being given sufficient time to evolve tolerance. The coral's algal partners have short lifetimes and possess genetic traits which may enable successful adaptation to warming. Coral themselves aren't so lucky, somewhat in contrast to their algae, they possess a poor genetic ability to combat warming stress and have decadal lifetimes. It's likely therefore that many coral will die because the speed of warming is too great within an individual communities lifetime.

Perhaps a useful way of looking at it, is that the "bar" is continually being set higher and higher, and the recovery time between bleaching events becoming smaller and smaller. Gradually this continual ocean warming will start to impact areas which have so far escaped unscathed, and these coral will succumb too. Of course coral reefs aren't just under fire from bleaching, as mentioned earlier, humans are hurting them in many other ways. Ocean Acidification in particular is a large looming threat (Veron 2009). The increasing frequency and severity of bleaching, coupled with the persistent decline in coral around the world, should however immediately dispel any myths about coral resilience.

2011-01-04 09:02:35
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.205.130

A bit long-winded (and I've trimmed it!). Advanced or intermediate?. Links and pictures on their way. 

My focus will be on ecological consequences primarily, which is kind of the whole point we're concerned about global warming. isn't it?. That's why the posts on coral diverge from strictly rebutting the silly arguments, I think a bit more education on the topic at hand might be useful. 

 

2011-01-07 08:15:06A very enjoyable read
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
212.139.85.64
I like this rebuttal - it may be a bit long but it's informative and it clearly illustrates the ways in which warmer waters affect coral reefs, with no clear sign of resilience. For me it's suitable as an intermediate rebuttal. Maybe it would benefit from being shorter but I don't see much wrong with it.
2011-01-07 20:15:12
nealjking

nealjking@gmail...
91.33.99.72

What is the intent of this sentence?

"In point of fact it would be hard to fathom what all the fuss is about."

2011-01-07 21:30:02
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.221.47
Neal, it's a reflection of the typical man/woman-in-the-street reaction. I've encountered it more than a a few times.  
2011-01-08 01:32:24
nealjking

nealjking@gmail...
91.33.99.72
I would suggest dropping the "In point of fact." It sounds like you're saying that, if you focus on the facts, there's no real problem.
2011-01-08 04:16:31comments
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.252

I think you could pretty much just do away with the opening paragraph regarding blog comments and such.  It's a bit superfluous.  I do like the heading on the first section though :-)

You've got an extra period in this sentence - "So what does this all have to do with the average man or woman in the street?."

Overall very good post.  I could see it being either intermediate or advanced.  Usually when talking about bleaching, 'skeptics' comment that corals survived warmer periods in the distant past.  As I understsand, corals today are much more susceptible to warming/bleaching/acidification than corals millions of years ago.  Might be worth discussing in the 'resistance is futile' section, or maybe leave it off for an Advanced version to cover.

2011-01-08 05:33:45
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.225.166

-Neal, I see what you mean.

-Dana, you're probably right about the opening paragraph, I'll change it. It is something that bugs me though, whilst politicians and society in general fart around and bicker, some very worrying things are happening out there in the real world. Stuff that once done, cannot be undone. Maybe I'll deal with it in a blog post, as my writing improves/evolves.

-As far as resilience in the past is concerned, I'm about to start on another coral rebuttal addressing that particular meme. It just so happened there were a few coral arguments on the list and, given how "skeptics" continually shift the goalposts, thought that it might be prudent to cover all the obvious canards on coral. 

Thanks for the input guys & girls. 

2011-01-08 07:14:12Ready
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
212.139.85.64

Ready to go. Just want to be a bit of a pain though (apologies) - in the first paragraph of the lowdown on coral bleaching, 'Although the polyp does feed using it's tentacles to snare food, the bulk of it's nutrition (90%+) comes from the algae' should be 'Although the polyp does feed using its tentacle to snare food, the bulk of its nutrition (90%+) comes from the algae'.


2011-01-08 09:46:27
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.218.138

No worries Anne-Marie, just a bad habit of mine. Now fixed. Attribution for the graphic and bleaching photos yet to be added.

 

2011-01-10 22:43:23
Anne-Marie Blackburn
Anne-Marie Blackburn
bioluminescence@hotmail.co...
212.139.80.87
Wantcha look at silly me? Forgot to give you the thumbs up, sorry.
2011-01-11 00:00:52Great rebuttal
John Cook

john@skepticalscience...
121.222.100.112
The length is not an issue as we can always write a basic shorter version.

I love the opening line "The Earth seems to be already convinced of global warming and is responding quickly". It reminds me of one the best pieces of advice for rebutting skeptics I ever heard from Naomi Oreskes: "don't make it about what they said versus what you said. Instead make it about what they said versus what nature is saying. The real world is more eloquent than we can ever be:-)

typo in 4th paragraph: "envronmental"

What do you think of bolding this line "Globally about 1% of coral is dying out each year.". Seems important to emphasize.

2011-01-13 16:11:44Published this
John Cook

john@skepticalscience...
121.222.100.112

Rob, hope you don't mind, I went ahead and made the few small typo changes and published this. Feel free to edit the rebuttal down the track if you wish to update it.

I would suggest a few months down the track, someone (preferably Rob) write a basic version of this rebuttal.

2011-01-13 21:50:45
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.67.12
Thanks. Yeah, I might get onto that basic version in a week or so. This one's a bit long.