[Coral-List] UV and coral respiration

[Boland, Gregory]

Coral-List,

I have seen a number of comments relating to the effect/impacts of UV
radiation on corals over the past few months.  I think there is one factor
that is being overlooked in these discussions.  I am not an optical
physicist, but I have had an interest in the subject that began with
underwater ultraviolet photography experiments back in the 1970's to study
coral behavior with time lapse movie cameras using no visible light.  It was
my understanding then that UV wavelengths (UV A, B, and C ranging from
400-200 nanometers) could only penetrate seawater a few meters.  This
estimate is a bit conservative according to references such as Smith and
Baker (1979).  However, in areas with "normal" levels of dissolved organic
material, surface values of biologically effective solar UV irradiance is
reduced to 10 percent at a depth of 6 meters and only 1 percent at a depth
of 12 meters.  These numbers increase to 12 and 24 meters respectively for
"low" levels of DOM. This information is presented in a nice UV summary
paper, "Solar ultraviolet radiation effects on biological systems," by
Diffey (1991) at this URL:

http://www.ciesin.org/docs/001-503/001-503.html

Before any general statements can be made about the impact of UV radiation
(or reduction of the ozone layer, etc) on corals, one must consider the
water depth where any significant impact could occur.  As a prominent
example, the Flower Garden Banks coral reefs in the Gulf of Mexico, with an
approximate live coral cover of 50 percent, occur in water depths no
shallower than 18 meters.

Smith R C and Baker K S 1979 Penetration of UV-B and biologically effective
dose-rates in natural waters Photochem. Photobiol. 29 311-23

Greg Boland
Minerals Management Service



-----Original Message-----
From: Sara Brogdon [mailto:gte405r at mail.gatech.edu] 
Sent: Tuesday, June 08, 2004 9:49 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] UV and coral respiration

Can anyone direct me to references that discuss the effect of UV on coral 
respiration? I'm familiar with research showing that UV inhibits 
photosynthesis in algae, but I'd like to connect this response by the
symbiont 
to a reactive response by the host. For example, does inhibited
photosynthesis 
in zooxanthellae (or exposure to increased UV) affect the interconversions 
between CO2 and HCO3- by the coral animal?  

Thanks,
Sara Brogdon
Georgia Institute of Technology
School of Biology
310 Ferst Drive
Atlanta, Georgia 30332-0230
gte405r at prism.gatech.edu
 
 
  

 

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