[Coral-List] Re: HadISST 1.1 data: Bleaching is not due to Global Warming

[Erik Stabenau]

Dear Coral-listers,

It is good to see contrasting views and critiques of our understanding of the causes behind coral bleaching.  Others, more qualified, can take issue with the details of interpretation of temperature data.  I want to take this opportunity to discuss the use and occasional mis-use of UV data.    It's a common misconception, showing both in the text of this article and in a recent review of an article I submitted for peer review, that if the annual average ozone content in the atmosphere is constant then corals annual average UV exposure will also be constant.  This isn't the case.  Many other factors influence the penetration of light through surface waters, including both particulate and dissolved components.  The primary factor affecting coral UV exposure, and perhaps more importantly the spectra impinging on the coral surface, is not low latitude ozone variation, its changes in the quantity and spectral properties of chromophoric dissolved organic matter.  For this reason, simply considering that ozone content is fairly stable in the tropics is not reason enough to disregard the potential importance of variation in UV light intensity and spectra in coral bleaching processes.  

I've included a few reference for review of the influence of dissolved components on the underwater light field and the influence of this light field on coral health. 

ZEPP, R. G. 2002. Solar Ultraviolet Radiation and Aquatic Biogeochemical Cycles. In E. W. Helbling and H. Zagarese [eds.], UV effects in aquatic organisms and ecosystems. Comprehensive Series in Photosciences. European Society for Photobiology.

ANDERSON, S., R. ZEPP, J. MACHULA, D. SANTAVY, L. HANSEN, and E. MUELLER. 2001. Indicators of UV exposure in corals and their relevance to global climate change and coral bleaching. Human and Ecological Risk Assessment 7: 1271-1282.

DUNNE, R. P., and B. E. BROWN. 1996. Penetration of solar UVB radiation in shallow tropical waters and its potential biological effects on coral reefs; Results from the central Indian Ocean and Andaman Sea. Marine Ecology-Progress Series 144: 109-118.

If anyone in the coral-list community would like to contact me directly to discuss this further, feel free, I'm here all the week  ;-) 
Cheers,

Erik R. Stabenau
National Research Council Post-doctoral Associate
NOAA-AOML
4301 Rickenbacker Cswy.
Miami, FL  33149
305.361.4397 phone
305.361.4392 fax



coral-list-request at coral.aoml.noaa.gov wrote:

>Dear Coral-listers,
>
>I know that I will shock the common belief on this very important topic. But
>the facts are the facts. I was myself surprised. So I decided to send this
>draft to the list before submission to a publication, hoping for comments or
>critics. Thanks a lot.
>A long version is available at request.
>
>HadISST 1.1 data : Coral Reef Mass Bleaching is not due to Global Warming.
>
>Martin Pêcheux, June 2004
>Nice University, 94260 Fresnes, France
>Email : martin-pecheux at wanadoo.fr
>
>
>Ultra-violets, at first often considered, are not in cause, as they have not
>increase in tropics, and there is no relationship between ozone drawdowns
>and bleaching events (Pêcheux, 1996a). Moisture deficit increases over warm
>pools in tropics (Flohn and Kapala, 1989, Graham, 1995), but it is of low
>probability that it induces in the 80¹s an hydrological pattern change great
>enough to be responsible of local new maxima 0.7°C above previous one. It
>would also rather increase nebulosity over warm waters ("cirrus anvil
>thermostat"). And of course there were summer dolldrum times with clear sky
>before 1979.
>  
>