Coral Spawning/Gulf of Mexico (fwd)

[Coral Health and Monitoring Program]

---------- Forwarded message ---------- 
Date: 21 Aug 1996 16:32:25 -0400 
From: "Deslarzes, Ken" <kdeslarzes at ocean.nos.noaa.gov> 
To: Coral Health and Monitoring Program <coral at aoml.noaa.gov> 
Subject: Coral Spawning/Gulf of Mexico 

From: Gregory S. Boland, Dept. of Oceanography, Texas A&M University, College 
Station, Texas 77843, USA.  Ph. 409-845-8387 

-Copy of a Press Release- 
Seven evenings after the full moon of July; Flower Gardens Banks National 
Marine Sanctuary (NW Gulf of Mexico), August 6, 1996.  The corals continue to 
surprise all the coral reef biologists, including this one after five years of 
observation and research.  I would have bet, along with virtually every one 
else, that the odds were very small of seeing any spawning at the Flower 
Gardens this early in August, but the Flower Gardens surprised us yet again. 
On the night of August 6th, seven evenings after the full moon of July 30, the 
Flower Gardens impressed a large number of volunteer research divers from 
Oceanographic Expeditions with a mass spawning event (albeit very reduced in 
comparison to previous year's events).  In comparison to other sites 
throughout the Atlantic and Caribbean during normal events, even a reduced 
mass spawning at the Flower Gardens appears quite spectacular. 

The first witnessed coral spawning occurred at 20:55 hrs CDT from both male 
and female Montastraea cavernosa.  One dive team also recorded a mass egg 
bundle release from a single Diploria strigosa head at 21:30 hrs.  This author 
entered the water at 21:45 and shortly after came across the head of a female 
M. cavernosa releasing rather loose aggregations of tiny eggs.  In previous 
years, this diecious species extruded much more agglutinated egg masses than 
what was seen this year in August.  Individual eggs rapidly separated from 
each other as they were expelled from each polyp. 

A total of three different species were seen spawning between a narrow time 
window of 20:55-22:20 hrs.  These included D. strigosa, Montastraea franksi 
and both sexes of M. cavernosa.  People on the vessel also reported a limited 
presence of a spawn slick on the water's surface roughly during the same 
period. 

Ten divers entered the water for a third dive sequence on the evening of 
August at 23:55 hrs.  None observed any evidence of spawning during their dive 
of approximately 35 minutes and no other coral eggs were observed on the 
surface for the rest of the evening up to at least 02:00 hrs of 7 August. 

The second night of the cruise did not result in any diver observations of 
spawning between the hours of 20:30-21:30 hrs but there were observations of 
coral egg bundles on the surface.  The species producing the egg bundles was 
not positively identified but appeared to be from a M. franksi.  Several heads 
of D. strigosa were observed and photographed by this author underwater in 
pre-spawning "setting stage".  The vast majority (>95%) of the other D. 
strigosa heads did not show any signs of a setting stage. 

A very brief appearance of egg bundles also appeared on the surface at 21:30 
hrs during the night of 8 August, 9 evenings after the full moon.  This is the 
time frame for the spawning of Colpophyllia natans, but the observed egg 
bundles were much smaller that the normal baby pea-sized C. natans egg 
bundles.  The observed bundles could have been from a single head due to the 
very short duration (2-3 min) the spawn drifted past the vessel. 

There is little doubt that the 3 or 4 September coral spawning event will be 
quite spectacular, but then, we have been fooled before.