[Coral-List] diver distance

Steve Mussman sealab at earthlink.net
Thu Aug 15 09:15:19 EDT 2013

Dear Gene,

Yes, in the long term (over geological time) nature has likely been more harmful to coral reefs and other ecosystems than humans. But then consider the fact that we humans haven't been here but for a small fraction of earth's existence and the proposition turns.

We really haven't had much time to over-fish, litter, chemically pollute, cut down mangroves and dump unhealthy levels of nutrients and sedimentation into our coastal waters. And don't forget we haven't been exposing those scores of happy snorkelers and divers to the wonders of what used to be thriving reefs but for a few fleeting seconds of earth's time.

So while oodles of money are flowing and the Keys economy is the best you have ever seen, have you ever stopped to consider the picture that is emerging for future generations to behold?   What will that ever popular Molasses Reef look like three decades from now? 

Maybe I'm just not finding enough comfort in the fact that nature can be harmful too. 


-----Original Message-----
>From: Eugene Shinn <eugeneshinn at mail.usf.edu>
>Sent: Aug 14, 2013 4:51 PM
>To: "coral-list at coral.aoml.noaa.gov" <coral-list at coral.aoml.noaa.gov>
>Subject: [Coral-List] diver distance
>Dear Listers, I just spent more than a month diving in the Keys and 
>photographing the corals I have photographed yearly since 1960. Un 
>fortunately there has been no noticeable improvement at those sites 
>(Grecian Rocks and Carysfort Reef). Have spent last few days catching up 
>on e-mail and scanning the various coral list threads. As a geologist it 
>was easy to identify with the comments by Dennis Hubbard. His Caribbean 
>work indicates a coral growth hiatus at 3,000 and 6,000 years bp (before 
>present). In the Keys we have documented a hiatus in /Acropora 
>cervicornis/ growth centered around 3000 years bp as well as one 
>centered at 4,500 ka. The 6 ka hiatus found by Hubbard is not present in 
>Florida Keys reefs because the shelf was being flooded and corals were 
>just beginning to grow at that time. This knowledge is based on Carbon 
>14 dating of corals at the base of coral reef cores. Although dating 
>verifies two major breaks in coral growth there were likely many more 
>during the past 6 ka (thousand years) when the so-called Florida reef 
>tract was being flooded during the world-wide Holocene rise. Frequent 
>waxing and waning occurred during that time because approximately 98 
>percent of that 150+ mile long reef tract has built up no more than 2 m 
>of coral accumulation. That knowledge is based on more than 20 years of 
>high resolution seismic profiling and ground truth coring 
><http://pubs.usgs.gov/pp/2007/1751>. In fact, a core adjacent to the 
>Aquarius habitat revealed only 15 cm of accumulation during the past 6 
>ka. In other words biologists studying that area have in fact have been 
>studying a hardground community that looks like a coral reef. That's ok 
>because they would get the same biological results studying corals etc. 
>on a true coral reef accumulation.
>True reef accumulations do occur in the keys but they are mainly in the 
>form of coral spurs and occur mainly on preexisting Pleistocene bedrock 
>highs. These are the named reefs that have kept pace with sea level rise 
>(about 2 percent of the reef tract). It is the cores of these 
>accumulations upon which our knowledge of Keys coral reef history is 
>based. Clearly there were climate related events (increased hurricanes? 
>fluxes of cold water? warming seas? diseases?) that kept the other 98 
>percent of the reef tract from developing along with those on the 
>bedrock highs.
>Yes, People have likely affected growth in the past 50-years but that 
>does not prove natural events were not equally harmful. In the long 
>term, as Hubbard says, nature has likely been more harmful than people.
>During this latest expedition I observed formidable examples of shifting 
>baselines or should we now call it the "new normal"? During our short 
>visit to Grecian Rocks we observed the arrival and departure of at least 
>5 large catamarans each of which disgorged 20 to 30 snorkelers, not 
>including the numerous private boatloads of snorkelers. I estimate that 
>around 200 swimmers snorkeled the leeward side of Grecian Rocks during 
>that day, and this was not even a weekend! I can only surmise that the 
>snorkelers were happy with what used to be a thriving reef and clearly 
>oodles of money was flowing into the Keys economy. After observing all 
>this activity the question of how close a diver should approach corals 
>seems moot. If the water is clear the divers appear to be happy and the 
>keys economy is flourishing like I have never seen during my 60 some odd 
>years of diving there. I wonder what it was like at the really popular 
>reefs such as Molasses reef?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
>---------------------------------- -----------------------------------
>Coral-List mailing list
>Coral-List at coral.aoml.noaa.gov

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