[Coral-List] coral sedimentation thresholds for dredge induced sedimentation
Gene Shinn
eshinn at marine.usf.edu
Thu Jan 25 13:25:17 EST 2007
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
--
No Rocks, No Water, No Ecosystem (EAS)
------------------------------------ -----------------------------------
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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