[Coral-List] An extensive reef system at the Amazon River mouth

Eugene Shinn eugeneshinn at mail.usf.edu
Tue Apr 26 14:38:42 EDT 2016

The rediscovery of a deep “reef” off the mouth of the Amazon is 
certainly an exciting newsmaker that once again demonstrates how little 
we really know about corals and their growth requirements. That there 
are corals living there is not all that surprising. Any geologist who 
has examined ancient reefs, whether built by corals or sponges, is aware 
that many in the past grew in the presence of muddy sediment. From the 
depths reported, (up to 125 meters), it seems clear the Brazilian reef 
tract began growing during the last glaciation when global sea level was 
approximately 125 m below present.The Amazon River at that time would 
likely have been much different. If the flow was anything like today it 
would probably have been focused through a narrow gap in the old reef 
line before discharging into deep water. Detailed seismic mapping of the 
area that most likely already exists, would reveal where that flow was 

Old shorelines consisting of beach dunes occur at similar depths around 
much of the Gulf of Mexico as well as along the eastern seaboard off the 
Florida Keys. It does not seem surprising that a rock ridge hosting many 
reef organisms should exist off the Brazilian coast beneath the Amazon 
mud plume. Ironically millions have been spent over the years on 
research related to possible effects of drilling mud on live corals and 
other bottom organisms near oil wells. Because of that concern 
exploration drilling in the Gulf of Mexico is precluded from hard bottom 
topographic accumulations created by natural oil and gas seepage. Such 
features host a multitude of chemosynthetic organisms including 
deep-water corals, worms, clams and crustaceans. I found it interesting 
that the /Atlantic/ article ends with concern that oil exploration might 
occur on this reef beneath the amazons mud plume. Gene


No Rocks, No Water, No Ecosystem (EAS)
------------------------------------ -----------------------------------
E. A. Shinn, Courtesy Professor
University of South Florida
College of Marine Science Room 221A
140 Seventh Avenue South
St. Petersburg, FL 33701
<eugeneshinn at mail.usf.edu>
Tel 727 553-1158
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