Coral Reef Bleaching Cause

Thisis a strong argument outlining a real and present danger associated with ourmassive outpouring of CO2 gas.  He alsogives lip service to the purported linkage of CO2 with so called global warmingthough as I have posted many times that is actually contraindicated by the bulkof the geological data.

However,from the get go, this blog has expressed concerns regarding CO2 production and haslooked for ways to deal with the dumped CO2. We have had some success in identifying methods for sequestering CO2,mostly by enriching agricultural soils with biochar to also eliminate chemical fertilization.

Thishas always been a case of the right problem and the wrong reason.

Thewriter becomes quite strident in his concerns and it takes some effort to getthrough to the main thesis.  It is thathigher CO2 is able to set conditions that cause the destruction of reefs.  Presently the effect is local, and with acouple of warm decades, rather common. We certainly need to take note.

However,at present, all indications support the proposition that temperatures haveentered decline and certainly flat lined a decade ago.  We likely have a couple of decades of coolerwaters ahead of us instead of the alternative. And yes, this winter is happening because conditions are able to beworse than five years ago.  Increasingsolar activity may well reverse that.

Thus,I am not so concerned, but I do want to see our civilization divert the CO2 weare producing as soon as possible.  I donot like unplanned experiments based on crapping in our own nest.

Coral reefs 'could disappear in ourchildren's lifetime'

Yale Environment 360:Unless we change the way we live, the Earth's coral reefs will be utterlydestroyed within our children's lifetimes, says marine scientist JEN Veron

J.E.N. Veron for Yale Environment 360, Tuesday 7 December 2010

One in four coral species are under threat of extinction. Photograph:Corbis

Over the past decades, there have dozens of articles in the mediadescribing dire futures for coral reefs.In the 1960s and '70s, we were informed that many reefs were being consumed bya voracious coral predator, the crown-of-thorns starfish. In the 1980s and'90s, although these starfish still reared their thorny heads from time totime, the principal threats had moved on — to sediment runoff, nutrients,overfishing, and general habitat destruction.

For me, an Australian marine scientist who hasspent the past 40 years working on reefs the world over, these threats were ofreal concern, but their implications were limited in time or in space or both.Although crown-of-thorns starfish can certainly devastate reefs, the impacts ofsediments, nutrients and habitat loss have usually been of greater concern, andI have been repeatedly shocked by the destruction I have witnessed. However,nothing comes close to the devastation waiting in the wings at the moment.

You may well feel that dire predictions aboutanything almost always turn out to be exaggerations. You may think there may besomething in it to worry about, but it won't be as bad as doomsayers like meare predicting. This view is understandable given that only a few decades agoI, myself, would have thought it ridiculous to imagine that reefs might have alimited lifespan on Earth as a consequence of human actions. It would haveseemed preposterous that, for example, the Great Barrier Reef — the biggeststructure ever made by life on Earth — could be mortally threatened by anypresent or foreseeable environmental change.

Yet here I am today, humbled to have spent themost productive scientific years of my life around the rich wonders of theunderwater world, and utterly convinced that they will not be there for ourchildren's children to enjoy unless we drastically change our priorities andthe way we live.

A decade ago, my increasing concern for the plight of reefs in the faceof global temperature changes led me to start researching the effects of climatechange on reefs, drawing on my experience in reef science,evolution, biodiversity, genetics, and conservation, as well as my profoundinterests in geology, palaeontology, and oceanography, not to mention thechallenging task of understanding the climate science, geochemical processes,and ocean chemistry.

When I started researching my book, A Reef in Time: The Great Barrier Reeffrom Beginning to End (Harvard, 2008), I knew that climate changewas likely to have serious consequences for coral reefs. But the big picturethat gradually emerged from my integration of these disparate disciplines leftme shocked to the core.

In a long period of deep personal anguish, I turned to specialists inmany different fields of science to find anything that might suggest a fault in my own conclusions.But in this quest I was depressingly unsuccessful. The bottom line remains:Science argues that coral reefs can indeed be utterly trashed in the lifetimeof today's children. That certainty is what motivates me to spread this messageas clearly, and accurately, as I can.

So what are the issues? Most readers will knowthat there have been several major episodes of mass bleaching on major reefareas worldwide over the past 20 years. In the late-1980s when the firstmass bleaching occurred, there was a great deal of concern among reefscientists and conservation organizations, but the phenomenon had no clearexplanation. Since then, the number and frequency of mass bleachings haveincreased and sparked widespread research efforts.

Corals have an intimate symbiotic relationshipwith single-celled algae, zooxanthellae, which live in their cells and providethe photosynthetic fuel for them to grow and reefs to form. The researchshowed that this relationship can be surprisingly fragile if corals are exposedto high light conditions at the same time as above-normal water temperatures,because the algae produce toxic levels of oxygen, and excessive levels ofoxygen are toxic to most animal life. Under these conditions, corals mustexpel the zooxanthellae, bleach, and probably die or succumb to the toxin anddefinitely die. A tough choice, one they have not had to make at any time intheir long genetic history.

We tend to think of temperature in terms ofour day-to-day comfort level. We don't have to be told that atmospherictemperature shows huge swings and variations from day to night, among seasons,and cyclically on other scales. Early critics of global warming used thisvariability to argue that there was no evidence for overall thermal increases. Thismissed the point and delayed our recognition of the true problem becauseatmospheric temperature is only a minor part of the Earth's thermal picture.

By far the most important mobile heat sinks onthe planet are the oceans. As the greenhouse effect from elevated CO2 hasincreased, the oceans have absorbed more heat. The surface layers are affected most asmixing to the depths can take hundreds of years. Large ocean masses such asthe Indo-Pacific Warm Pool do not continue to warm further, but rather theybroaden and deepen. Now they commonly become so large that their outer edgesare pulsed onto the continental margins, where waters are warmed further.This creates the mortal dilemma for corals — to expel or not to expel theiroxygen-producing zooxanthellae.

Ecosystems can recover from all sorts of abuse, and coral reefs are noexception. Good recoveries from bleaching have been observed, provided that further events donot occur while the ecosystem is re-establishing. Unfortunately, there are nosigns that greenhouse gas increases are moderating, and so we can assume thatthe frequency and severity of bleaching events will continue to increase — on ourpresent course, the worst bleaching year we have had to date will be an averageyear by 2030, and a good year by 2050. Ocean and atmospheric rises intemperature are also predicted to increase the severity of cyclones, which willadd an extra burden on the recovery process.

Scientists don't need a pocket calculator toconclude that compressing the time periods between events in this way willprevent recovery: If we do not take action, the only corals not affected bymass bleaching by 2050 will be those hiding in refuges away from strongsunlight.

But there is more bad news. A decade or soago, we thought that mass bleaching was the most serious threat to coral reefs.How wrong we were. It is clear now that there is a much more serious crisis onthe horizon — that of ocean acidification. This will not only affect coralreefs (although reefs will be hit particularly hard), but will impact allmarine ecosystems. The potential consequences of ocean acidification arenothing less than catastrophic. The ultimate culprit is still CO2 but themechanism is very different.

Normally there is a balance between CO2 in theatmosphere and its derivatives in surface waters of the ocean. As withtemperature, the oceans act as a huge repository, absorbing and buffering any excessCO2 in the atmosphere. For this process to be efficient the oceans must havetime for mixing to occur between its different layers, renewing the surfacebuffers from below. When CO2 increases too rapidly, these chemical reactionscan falter, altering the balance of the buffers and gradually allowing theoceans to become less alkaline.

All organisms that produce calcium carbonateskeletons (including shells, crabs, sea urchins, corals, coralline algae,calcareous phytoplankton, and many others) depend on their ability to depositcalcium carbonate, and this process is largely controlled by the prevailingwater chemistry. As alkalinity decreases, precipitation of calcium carbonatebecomes more and more difficult until eventually it is inhibited altogether.The potential consequences of such acidification are nothing less thancatastrophic.

In my book, I examine the events that led upto each of the five mass extinctions in Earth's history. Corals offer a uniqueinsight into the past, both because they have been around for most of thehistory of life on Earth and also because they readily fossilize. I examine thetheories offered to explain these global extinctions and find that oceanacidification is the only explanation which fits the evidence well. Oceanacidification has played a major part in the marine devastations which tookplace in those ancient times.

A particularly galling aspect of the past fourmass extinction events (very little is known about the first) is that,following them, reefs disappeared — not just for a few tens of thousands ofyears, but for millions of years — long after adverse climatic conditions mayhave returned to benign levels. One of the characteristics of acidification isthat while it can be initiated by high CO2 levels over relatively shortperiods, there are no short-term geochemical fixes to reverse the process.Reversal can take place only through the immensely slow weathering anddissolution processes of geological time, processes that take hundreds ofthousands to millions of years.

Ocean physics dictates that we will observethe effects of acidification in colder and deeper waters before it spreads toshallower tropical climes. The early stages of acidification have now beendetected in the Southern Ocean and, surprisingly perhaps, in tropical corals.On our current trajectory of increasing atmospheric CO2, we can expect that by2030 to 2050 the acidification process will be affecting all the oceans of theworld to some degree. At that point, the relatively cool, deep-water tropicalregions that have offered refuges to corals from temperature stress will bethose most affected by acidification.

No doubt different species of coral, corallinealgae, plankton, and mollusks will show different tolerances, and theircapacity to calcify will decline at different rates. But as acidificationprogresses, they will all suffer from some form of coralline osteoporosis. Theresult will be that corals will no longer be able to build reefs or maintainthem against the forces of erosion. What were once thriving coral gardens thatsupported the greatest biodiversity of the marine realm will become red-blackbacterial slime, and they will stay that way.

Another concept of great importance is that of commitment — a wordclimatologists use only too often. Many of the consequences of our currentactions cannot yet be seen, and yet the Earth is already committed to their path. Thisdelayed reaction is due to the inertia of the oceans, both thermal andchemical. The greenhouse gases we produce today will take a number of decades(and sometimes more) to unleash their full fury, but their effects areunavoidable and unstoppable. We cannot afford to wait until the predictions ofscience can be totally verified, because by that time it will be too late. Howmany of us wish to explain to our children and children's children that thepredictions were there but we wanted confirmation?

Coral reefs speak unambiguously about climate change. They survived IceAge sea-level changes of 120 meters or more with impunity. They once survivedin a world where CO2 from volcanoes and methane was much higher than anythingpredicted today. But that was over 40 million years ago, and the increase tookplace over millions of years, not just a few decades, time enough for oceanequilibration to take place and marinelife to adapt.

This is not what is happening today. Ponderthese facts: The atmospheric levels of CO2 we are already committed to reach,no matter what mitigation is now implemented, have no equal over the entirelongevity of the Great Barrier Reef, perhaps25 million years. And most significantly, the rate of CO2 increase we are nowexperiencing has no precedent in all known geological history.

Reefs are the ocean's canaries and we musthear their call. This call is not just for themselves, for the other greatecosystems of the ocean stand behind reefs like a row of dominoes. If coralreefs fail, the rest will follow in rapid succession, and the Sixth MassExtinction will be upon us — and will be of our making.

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