[Coral-List] coral sedimentation thresholds for dredge induced sedimentation

[Gene Shinn]

This is a question that comes up time-and-time-again. To my knowledge 
the definitive research has not been conducted and probably never 
will be. Plenty of review articles. Most are anchored on the 1930s 
Great Barrier reef expedition experiments that were mainly about 
burial of corals under sediment. Burial will kill.  Caroline Rogers 
review paper is a good place to start.
     There were 24 papers  on muddy water corals given at a special 
session of the Bali 2000 ICRS meeting but it was mainly about corals 
that normally live under those conditions. Most people do not know 
about them because who wants to go diving in such places in the first 
place and besides, they do provide very good underwater photographs. 
Divers around Key West will remember that lots of healthy corals were 
growing on the seawall at Key West harbor where the cruise ships 
stir up the bottom almost every day. On a sea wall they can not get 
buried. Nevertheless they were transplanted before dredging of the 
harbor began but again there was no hard data on which to base that 
action.  Of course a lot depends on how long the dredging will last. 
If  you are talking about dredging on a reef just remember that the 
wave and current conditions where most reef building corals thrive 
will not allow fine grained sediment to settle or stay very long.  If 
it did the mud transported over the Florida Keys reefs during 
hurricanes (and stirred up for months after),  would have smothered 
them long ago.  It is no secret that the healthiest reefs in the 
Florida Keys today are the Hawk Channel patch reefs in the lower keys 
where visibility is seldom over 10-15 ft.  Hey, I am not advocating 
dredging..I'm just advocating that someone should do the hard science.
OK Mike, its your turn. Gene
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No Rocks, No Water, No Ecosystem (EAS)
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E. A. Shinn, Courtesy Professor
University of South Florida
Marine Science Center (room 204)
140 Seventh Avenue South
St. Petersburg, FL 33701
<eshinn at marine.usf.edu>
Tel 727 553-1158---------------------------------- 
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