GBR Coral Growth Study from AIMS 28


This newly released study from the Australian Institute of Marine Science in Townsville is getting a lot of press. An interview with the author Glen De’ath by the ABC claims a tipping point for coral growth has already been reached in 1990. Mongabay.com claims the growth of coral in Australia’s Great Barrier Reef has slowed its lowest rate in at least 400 years as a result of warming waters and ocean acidification.

The claims are made on the basis of data apparently showing the rate of calcification from 328 colonies of massive Porites corals from 69 reefs of the Great Barrier Reef (GBR) has declined by 14.2% since 1990. These data would seem to be worthwhile checking by independent sources. Abstract from Science below, a News of the Week article by Elizabeth Pennisi. As the claims are based essentially on an upside-down hockey stick, there seems to be a contradiction in the abstract.

Declining Coral Calcification on the Great Barrier Reef
Glenn De’ath,* Janice M. Lough, Katharina E. Fabricius

Reef-building corals are under increasing physiological stress from a changing climate and ocean absorption of increasing atmospheric carbon dioxide. We investigated 328 colonies of massive Porites corals from 69 reefs of the Great Barrier Reef (GBR) in Australia. Their skeletal records show that throughout the GBR, calcification has declined by 14.2% since 1990, predominantly because extension (linear growth) has declined by 13.3%. The data suggest that such a severe and sudden decline in calcification is unprecedented in at least the past 400 years. Calcification increases linearly with increasing large-scale sea surface temperature but responds nonlinearly to annual temperature anomalies. 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.

Australian Institute of Marine Science, Townsville, Queensland 4810, Australia.

How can calcification simultaneously increase linearly with increasing sea surface temperature, and at the same time, have remained relatively constant over the last 400 years? Either sea surface temperatures were constant, or calcification rate did not respond to temperature.

Update: jae pointed to some contradictory studies.
Crabbe, M.J.C., Wilson, M.E.J. and Smith, D.J. 2006. :

Crabbe et al. report, first of all, that the Quaternary corals they studied appear to have grown “in a comparable environment to modern reefs at Kaledupa and Hoga,” except, of course, for the air’s CO2 concentration, which is currently higher than it has been at any other time throughout the entire Quaternary, i.e., the past 1.8 million years. Second, the results of their measurements indicate that the radial growth rates of the modern corals are 31% greater than those of their more ancient Quaternary cousins, in the case of Porites species, and 34% greater in the case of Favites species.

Review of long-term coral data sets:

So what did Bessat and Buigues find? First of all, they found that a 1°C increase in water temperature increased coral calcification rate at the site they studied by fully 4.5%. Then they found that “instead of a 6-14% decline in calcification over the past 100 years [as] computed by the Kleypas group, the calcification has increased, in accordance with [what] Australian scientists Lough and Barnes [found].” They also observed patterns of “jumps or stages” in the record, which were characterized by an increase in the annual rate of calcification, particularly at the beginning of the past century “and in a more marked way around 1940, 1960 and 1976,” stating once again that their results “do not confirm those predicted by the Kleypas et al. (1999) model.”

There seems a variation from other results in the field.

  • JaneHM

    David

    According to the BBC write-up on the paper, the massive corals are growing at a rate of 1.5 cm per year. A 13.3% decline in the growth rate means that today the corals are growing 2mm (millimeters) less this year than they did in 1990. How can the claim of such accuracy be statistically valid? Additionally, the surface of a coral of rough, not smooth, on the scale of centimeters.
    http://news.bbc.co.uk/2/hi/science/nature/7807943.stm

  • JaneHM

    David

    According to the BBC write-up on the paper, the massive corals are growing at a rate of 1.5 cm per year. A 13.3% decline in the growth rate means that today the corals are growing 2mm (millimeters) less this year than they did in 1990. How can the claim of such accuracy be statistically valid? Additionally, the surface of a coral of rough, not smooth, on the scale of centimeters.
    http://news.bbc.co.uk/2/hi/science/nature/7807943.stm

  • jae

    CO2 science.org has summaries of many studies that don’t agree with the one you cited.

  • jae

    CO2 science.org has summaries of many studies that don’t agree with the one you cited.

  • Franko

    #1 JaneHM
    // “How can the claim of such accuracy be statistically valid? Additionally, the surface of a coral of rough, not smooth, on the scale of centimeters.”

    Establish an undersea benchmark, a reflector of sonar, as the reference to compare against. Bounce the sonar and get all kinds of relations, such as coral height, density etc.

    Additionally, above the water, differential GPS can achieve construction survey grade, near millimeter accuracy.

  • Franko

    #1 JaneHM
    // “How can the claim of such accuracy be statistically valid? Additionally, the surface of a coral of rough, not smooth, on the scale of centimeters.”

    Establish an undersea benchmark, a reflector of sonar, as the reference to compare against. Bounce the sonar and get all kinds of relations, such as coral height, density etc.

    Additionally, above the water, differential GPS can achieve construction survey grade, near millimeter accuracy.

  • kuhnkat

    A quote from the author:

    “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.”

    He must be so proud of his published HYPOTHESIS, or, is there enough there to be an actual THEORY?!?!

  • kuhnkat

    A quote from the author:

    “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.”

    He must be so proud of his published HYPOTHESIS, or, is there enough there to be an actual THEORY?!?!

  • Anonymous

    I would like to work out where this study stands in the Oxford Evidence Scale. Probably one of:

    3. Systematic review of case-control studies with worrisome heterogeneity
    4. Case-series (and poor quality prognostic cohort studies)
    5. Expert opinion without explicit critical appraisal, or based on physiology, bench research or ‘first principles’

  • http://landshape.org/enm admin

    I would like to work out where this study stands in the Oxford Evidence Scale. Probably one of:

    3. Systematic review of case-control studies with worrisome heterogeneity
    4. Case-series (and poor quality prognostic cohort studies)
    5. Expert opinion without explicit critical appraisal, or based on physiology, bench research or ‘first principles’

  • jae

    Note the most important words in that conclusion: “MAY BE”. DOES the study demonstrate, in any way, that it IS diminishing the ability of GBR corals to deposite CaCO3? Probably not, since the words “MAY BE” are used. But this kind of weak, inconclusive “conclusion” seems to pass muster in climate science journals these days. Problem is that many, especially media types and AGW zealots, don’t see the all-important MAY BE limitation.

  • jae

    Note the most important words in that conclusion: “MAY BE”. DOES the study demonstrate, in any way, that it IS diminishing the ability of GBR corals to deposite CaCO3? Probably not, since the words “MAY BE” are used. But this kind of weak, inconclusive “conclusion” seems to pass muster in climate science journals these days. Problem is that many, especially media types and AGW zealots, don’t see the all-important MAY BE limitation.

  • Anonymous

    In other words, the conclusion concerning aragonite is probably level 5 evidence (the lowest least reliable), and the evidence of decline is probably level 4 reliability. Quite a disjunct from the breathless claims.

  • http://landshape.org/enm admin

    In other words, the conclusion concerning aragonite is probably level 5 evidence (the lowest least reliable), and the evidence of decline is probably level 4 reliability. Quite a disjunct from the breathless claims.

  • jae

    Exactly!

  • jae

    Exactly!

  • Geoff Sherrington

    The self-appointed expert on oceans and AGW might be Richard Feely of Oak Ridge National Labs, in relation to FACE projects. Easy to find in IPCC and a large paper trail from there. I emailed him if anyone had done the simple experiment of adding CO2 to seawater to measure the pH change and got no answer. I did this because his work is model, model, model and phase diagrams – which have any a tiny margin for error to be spurious.

    Feely maintains that man-made CO2 has caused a drop of 0.1 in pH in the oceans and this affects the amount of calcium available for coral building. But I was not able to discover if the 0.1 pH was for a surface onion slice of the oceans or for the whole ocean. Hence the titration suggestion.

    The phase diagram theory is basically as I was taught but the subtle quantitative movement probably needs more work if it is important enough. Feedbacks happen. Corals have been around for a long time and seem to be able to survive geological cycles of some modelled severity. And remember that the pH scale is non-linear, so that things that happen in poorly buffered, high alkaline environments do not happen so much in heavily buffered, acid environs.

    ORNL used to sell graphite blocks in their museum souvenir bookshop, from the first reactor. I also bought the magnificent Great Scientific American Paper Airplane Book there in 1978 or so.

    Now ORNL are mucking around with seawater. Whatever happened to core nuclear research?

  • Geoff Sherrington

    The self-appointed expert on oceans and AGW might be Richard Feely of Oak Ridge National Labs, in relation to FACE projects. Easy to find in IPCC and a large paper trail from there. I emailed him if anyone had done the simple experiment of adding CO2 to seawater to measure the pH change and got no answer. I did this because his work is model, model, model and phase diagrams – which have any a tiny margin for error to be spurious.

    Feely maintains that man-made CO2 has caused a drop of 0.1 in pH in the oceans and this affects the amount of calcium available for coral building. But I was not able to discover if the 0.1 pH was for a surface onion slice of the oceans or for the whole ocean. Hence the titration suggestion.

    The phase diagram theory is basically as I was taught but the subtle quantitative movement probably needs more work if it is important enough. Feedbacks happen. Corals have been around for a long time and seem to be able to survive geological cycles of some modelled severity. And remember that the pH scale is non-linear, so that things that happen in poorly buffered, high alkaline environments do not happen so much in heavily buffered, acid environs.

    ORNL used to sell graphite blocks in their museum souvenir bookshop, from the first reactor. I also bought the magnificent Great Scientific American Paper Airplane Book there in 1978 or so.

    Now ORNL are mucking around with seawater. Whatever happened to core nuclear research?

  • http://www.timcurtin.com Tim Curtin

    With apologies for cross-posting, here is what I offered at Jennifer Marohasy’s yesterday: re the De’ath et al article, first the title: “Declining oral Calcification on the Great Barrier Reef” seems to imply that the absolute extent of the GBR is “declining”, and some media have understood that to be the message of the paper. However the text clarifies that declining “calcification RATES” (in grams per square centimetre p.a.) are what the paper seeks to establish. Thus on page 117 we are told that the “rate of calcification has declined since 1990 “from 1.76 to 1.51 g/cm2/p.a.”, but we are not told what percentage 1.75 g/cm2 is of the average structure of the samples in question. If that was 1000 g/cm2, the decline seems marginal, or even if 100 g/mc2, still not huge, from growth in that case from 1.76% pa to 1.51%. But if language counts for anything at Science it is clear that calcification at the GBR is still growing, albeit somewhat more slowly, with growth having fallen by 0.25 g/cm2/pa, or 14.2%, between 1990 and 2005. Apparently the rate of decline (i.e. second derivative) increased from 0.3% pa to 1.5% in 2005 but as we are not told what the historic growth rate is – is it 10% pa or 20%? – how do we know whether a 1.5% decline in that rate is big or small? For example, if the historic growth rate was 10% pa. then a decline of 1.5% in that rate reduces it to 9.85%, hardly exciting enough for the hysterical media releases that heralded the De’ath paper.

    Moreover as is predictable for this kind of paper, it uses 1990 as start year, but that was a cool high growth La Nina year, while its end year 2005 was a hot low growth El Nino, but then why one would expect De’ath & co and their Institute to have heard of ENSO and its impact on climate at the GBR?

    At least Science’s Elizabeth Pennisi in her Comment on the De’ath paper noted the finding by Alina Szmant at UNC Wilmington “that it’s not clear that carbon dioxide enrichment will have negative effects on calcification rates”, or that either “lower pH or lower CaCo3 [resulting from acidification] will reduce calcification”. I noted before here that De’ath & co scarcely mention the carbonate involved in coral formation, as their stress on calcification implies that calcium is the only coral building block, until their final page, and then they state that with declining calcification “maintenance of the calcium carbonate structure that is the foundation of the GBR will be severely compromised”. Has there been a decline in marine calcium available for formation of aragonate (i.e. CaCo3)? No data from De’ath. Clearly if he et al. are right, there is no shortage of CO2 to help produce the CaCo3. As Jen notes, the paper even admits growth rates seem higher in the hotter northern section of the GBR than in the colder southern stretches.

    Until AGW took over Science, it used to involve precise terminology and measurement. Both are absent from the De’ath paper (and from its so-called “Supporting Material”, which provides no data at all, not even on the alleged declining pH at the GBR for which it provides no evidence even though it is touted upfront as the “cause” of the “declining calcification”).

  • http://www.timcurtin.com Tim Curtin

    With apologies for cross-posting, here is what I offered at Jennifer Marohasy’s yesterday: re the De’ath et al article, first the title: “Declining oral Calcification on the Great Barrier Reef” seems to imply that the absolute extent of the GBR is “declining”, and some media have understood that to be the message of the paper. However the text clarifies that declining “calcification RATES” (in grams per square centimetre p.a.) are what the paper seeks to establish. Thus on page 117 we are told that the “rate of calcification has declined since 1990 “from 1.76 to 1.51 g/cm2/p.a.”, but we are not told what percentage 1.75 g/cm2 is of the average structure of the samples in question. If that was 1000 g/cm2, the decline seems marginal, or even if 100 g/mc2, still not huge, from growth in that case from 1.76% pa to 1.51%. But if language counts for anything at Science it is clear that calcification at the GBR is still growing, albeit somewhat more slowly, with growth having fallen by 0.25 g/cm2/pa, or 14.2%, between 1990 and 2005. Apparently the rate of decline (i.e. second derivative) increased from 0.3% pa to 1.5% in 2005 but as we are not told what the historic growth rate is – is it 10% pa or 20%? – how do we know whether a 1.5% decline in that rate is big or small? For example, if the historic growth rate was 10% pa. then a decline of 1.5% in that rate reduces it to 9.85%, hardly exciting enough for the hysterical media releases that heralded the De’ath paper.

    Moreover as is predictable for this kind of paper, it uses 1990 as start year, but that was a cool high growth La Nina year, while its end year 2005 was a hot low growth El Nino, but then why one would expect De’ath & co and their Institute to have heard of ENSO and its impact on climate at the GBR?

    At least Science’s Elizabeth Pennisi in her Comment on the De’ath paper noted the finding by Alina Szmant at UNC Wilmington “that it’s not clear that carbon dioxide enrichment will have negative effects on calcification rates”, or that either “lower pH or lower CaCo3 [resulting from acidification] will reduce calcification”. I noted before here that De’ath & co scarcely mention the carbonate involved in coral formation, as their stress on calcification implies that calcium is the only coral building block, until their final page, and then they state that with declining calcification “maintenance of the calcium carbonate structure that is the foundation of the GBR will be severely compromised”. Has there been a decline in marine calcium available for formation of aragonate (i.e. CaCo3)? No data from De’ath. Clearly if he et al. are right, there is no shortage of CO2 to help produce the CaCo3. As Jen notes, the paper even admits growth rates seem higher in the hotter northern section of the GBR than in the colder southern stretches.

    Until AGW took over Science, it used to involve precise terminology and measurement. Both are absent from the De’ath paper (and from its so-called “Supporting Material”, which provides no data at all, not even on the alleged declining pH at the GBR for which it provides no evidence even though it is touted upfront as the “cause” of the “declining calcification”).

  • Anonymous

    Thanks Tim. The posts here are pointers to JM’s blog where there is extensive discussion of this paper. I suspect the connection to AGW was added, disingenuously, to get it published in Science. Otherwise, it just says that a couple of bleaching events reduce calcification – not very startling. Elizabeth Pennisi seems to flag the possibility that the link is tenuous too.

  • http://landshape.org/enm admin

    Thanks Tim. The posts here are pointers to JM’s blog where there is extensive discussion of this paper. I suspect the connection to AGW was added, disingenuously, to get it published in Science. Otherwise, it just says that a couple of bleaching events reduce calcification – not very startling. Elizabeth Pennisi seems to flag the possibility that the link is tenuous too.

  • Jan Pompe

    guys

    Moreover as is predictable for this kind of paper, it uses 1990 as start year, but that was a cool high growth La Nina year, while its end year 2005 was a hot low growth El Nino, but then why one would expect De’ath & co and their Institute to have heard of ENSO and its impact on climate at the GBR?

    I am a little confused I had thought La Nina meant warmer West Pacific cooler East Pacific and vice versa for El Nino, so during the La Nina won’t the GBR be warmer than during El Nino?

  • Jan Pompe

    guys

    Moreover as is predictable for this kind of paper, it uses 1990 as start year, but that was a cool high growth La Nina year, while its end year 2005 was a hot low growth El Nino, but then why one would expect De’ath & co and their Institute to have heard of ENSO and its impact on climate at the GBR?

    I am a little confused I had thought La Nina meant warmer West Pacific cooler East Pacific and vice versa for El Nino, so during the La Nina won’t the GBR be warmer than during El Nino?

  • JaneHM

    Franko

    Sonar doesn’t give millimeter accuracy. Sonar speed is about 1,500 m/s and the wavelengths are greater than 1 centimeter

  • JaneHM

    Franko

    Sonar doesn’t give millimeter accuracy. Sonar speed is about 1,500 m/s and the wavelengths are greater than 1 centimeter

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