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

Michael Risk riskmj at univmail.cis.mcmaster.ca
Thu Jan 25 20:56:15 EST 2007

Hi Gene. You asked for it.

A short answer:

Caribbean corals, 10mg/l SPM.  (Cortes and Risk, Porter, yadda yadda.)

Indo-Pacific: research not done.

Forget NTU's, they are useless.

A short rant: Little good research has in fact been done on the effects
of sedimentation on corals, compared with the known effects this has on
reefs. This has been an oversight which in my opinion is a black eye
for the research community. Much of what has been published has been
done by biologists with little or no knowledge of sediments, and with
(apparently) not much interest in finding out. Twenty years after the
first work, there still is no agreement on standardisation of sediment
trap design, one of the basics. And on and on.


On Thu, 25 Jan 2007 13:25:17 -0500
 Gene Shinn <eshinn at marine.usf.edu> wrote:
> 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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Mike Risk
Marine Ecologist
PO Box 1195
Durham Ontario
N0G 1R0

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