[Coral-List] From a Keys farmer
acohen at whoi.edu
Fri Apr 6 17:04:23 EDT 2007
I'm not sure that the Fine and Tcherov article, as interesting as it is,
should be interpreted to mean that decalcified corals can survive and
recover in the real world, where - unlike in the experimental setting -
predation and competition for space would pose significant threats to
naked polyps. Corals build skeletons for good reason. It is instructive
that the decalcified polyps in the experiments began to precipitate
carbonate immediately on being transferred back to supersaturated
seawater conditions. Why bother to spend energy building an intricate
skeleton if its OK to go naked?
Dr. Stephen Jameson wrote:
>See the latest issue of Science (30 March 2007, page 1811) for an
>interesting research paper by Maoz Fine and Dan Tcherov:
>"Scleractinian Coral Species Survive and Recover from Decalcification".
>Dr. Stephen C. Jameson, President
>Coral Seas Inc. - Integrated Coastal Zone Management
>4254 Hungry Run Road, The Plains, VA 20198-1715 USA
>Office: 703-754-8690, Fax: 703-754-9139
>Email: sjameson at coralseas.com
>Web Site: http://www.coralseas.com
>Smithsonian National Museum of Natural History
>Washington, DC 20560
>>I think your observations and questions about CCA growth rates are very
>>insightful and worth further research. Mark made the point that
>>carbonate saturation state is [partially] controlled by temperature and
>>pCO2, which is correct, but these are not the only variables that
>>control saturation state. Nor are temperature and saturation state the
>>only variables that control calcification rate.
>>First, from what I know, there is little information on what controls
>>coralline algal growth and calcification, and it would be great to
>>supplement your long-term observations with good environmental data from
>>your culture site. I can imagine that there are several possible
>>environmental changes associated with your autumn "bloom" of CCA, such
>>as a decrease in temperature, a change in light regime, a change in
>>calcium carbonate saturation state (which is seasonally affected by
>>several factors such as alkalinity and temperature), nutrient levels, or
>>simply a combination of variables that triggers the algae to grow.
>>While there is good evidence that future changes in carbonate chemistry
>>will increasingly be a factor in calcification rates (and dissolution
>>rates!), given the complexity of these systems, I would hesitate to
>>point solely to carbonate chemistry as the trigger for your bloom.
>>For example, as temperature drops (and all other variables stay the
>>same), the saturation state would actually decrease. But if there is a
>>macroalgal bloom going on at the same time, then it is possible that the
>>photosynthetic CO2 drawdown would lead to an increase in saturation state.
>>Second, the few data on how saturation state might control coralline
>>algae calcification rates are confusing. There is some evidence that
>>saturation state controls calcification rate (e.g. Chris Langdon's work
>>in the Biosphere 2 mesocosm, which was dominated by coralline algae).
>>There is other evidence that coralline algae recruitment declines with
>>decreasing saturation state. But ongoing experiments (presentation by
>>Sophie Martin and JP Gattuso at the ASLO meeting) seem to paint a more
>>complicated picture, in which as you suggest, there is an interaction
>>between both saturation state AND temperature.
>>You make a great point: "It would be interesting to see some large
>>scale/long term field research on this topic as we struggle with the
>>questions surrounding globally rising temperatures and CO2." Perhaps
>>your CCA site is a good candidate for this kind of monitoring! To shed
>>light on which factors are stimulating the CCA blooms, this would
>>require long-term monitoring of at least temperature, salinity, light,
>>saturation state and nutrients. It would also be great if you could
>>measure *true* calcification rates rather than extension rates.
>>Unfortunately, both carbonate chemistry and calcification rates are
>>challenging measurements, and the "Impacts of Ocean Acidification on Coral
>>Reefs and Other Marine Calcifiers - Guide for Future Research" that Mark
>>and Chuck mentioned provides a summary of those challenges.
>>apologies for the lengthy message,
>>terrasubaqua at peoplepc.com wrote:
>>>I would add a personal observation to the global warming discussion based on
>>>ten years (~4 one week visits /yr) at the same spot off Plantation Key.
>>>There is a fundamental chemistry link between the solubility of calcium salts
>>>and water temperature, and we can see the local biochemical link to crustose
>>>coralline algae (CCA) growth rate at work each Fall. During this seasonal
>>>change, our aquaculture substrate coquina rock gathers a nice coating of CCA
>>>over a period of several weeks, commencing just as the water temperature
>>>drops. The CCA appears to cover substrate much more rapidly in the Fall
>>>months than at any other time of year, it's a very colorful phenomenon and
>>>one we watch closely because CCA means added value to our live rock products.
>>>We see that, with other variables held to a (roughly) narrow range, the rate
>>>of CCA coverage growth seems largely related to the degree of saturation of
>>>the calcium salts in the seawater.
>>>This may have global ramifications, with global water temperatures rising and
>>>considering the significance of calcium carbonate deposition to the global
>>>sequestration of carbon dioxide. I wonder how rising water temperatures
>>>affect the global deposition of calcium carbonate? Though we might assume
>>>from controlled experiments it would be detrimental, some biological factors
>>>such as faster overall growth, reproduction rate, and/or coverage of CCA in
>>>warmer water, or over water temperature changes spanning particular ranges,
>>>might control natural feedback mechanism(s) assisting CCA (and possibly other
>>>calcium carbonate 'bio-consumers'?) in global- scale sequestration. Even
>>>though CCA seems to grow much more slowly (if at all) in mid-winter at our
>>>site, the warmer global water temperatures we encounter may also enhance
>>>reproduction or otherwise benefit overall growth over the span of a year. It
>>>would be interesting to see some large scale/long term field research on this
>>> we struggle with the questions surrounding globally rising temperatures and
>>>Coral-List mailing list
>>>Coral-List at coral.aoml.noaa.gov
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Dr Anne L. Cohen
Department of Geology and Geophysics
Woods Hole Oceanographic Institution
508 289 2958 (tel)
508 457 2175 (fax)
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