[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
concentrated.
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
http://www.theatlantic.com/science/archive/2016/04/scientists-discover-a-new-coral-reef-at-the-amazons-mouth/479259/?utm_source=yahoo
--
No Rocks, No Water, No Ecosystem (EAS)
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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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