[Coral-List] Spawning Flower Garden Banks

George Schmahl George.Schmahl at noaa.gov
Tue Aug 26 11:19:52 EDT 2003

The following is a report of coral (and other reef organism) spawning at
the Flower Garden Banks in the northwestern Gulf of Mexico.
Observations were made during the evenings of August 18, 19, 20 and 21.

G.P. Schmahl (NOAA / Flower Garden Banks National Marine Sanctuary
Emma Hickerson (FGBNMS)
Dr. Peter Vize (University of Calgary)
Doug Weaver (FGBNMS)
Eric Borneman (University of Houston)
Jenn DeBose (University of California at Davis)
and others...

Most coral species spawned at the predicted times, but it was the
general consensus that the percentage of colonies actively spawning was
greatly reduced compared to 2002 and most previous years.  It is not
possible to give accurate percentage participation because quantitative
data was not collected on that parameter.  We intend to monitor possible
coral spawning activity after the full moon in September to see if
additional spawning occurs at that time.  Absent from this years
expected observations were activity by Montastrea annularis (the less
common of the three morphs) and females of Stephanocoenia intersepta.
In addition, in contrast to previous years, no observations of spawning
by the christmas tree worm (Spirobranchus giganteus) were recorded.

The local time of sunset (Galveston, TX) was between 1954 and 1957
during the period of observation.

Local state of reef:  The reefs of the East and West Flower Garden Banks
are very healthy, with an average of 50% living coral cover.  The
primary reef building species are the Montastrea annularis complex,
Diploria strigosa, Porites astreoides and Montastrea cavernosa.
Branching corals of the genus Acropora are absent.  Coral disease is
minimal.  No significant bleaching was observed.

Water temperature during the observation period averaged about 27
degrees C.  This is slightly cooler than average water temperatures for
this time of year.

August 18, 2003
West Flower Garden Bank - 27 degrees 52' 31" / 93 degrees 49' 4 "
Species:  Montastrea cavernosa, Montastrea franksi, Diploria strigosa,
Stephanocoenia intersepta.
Depth:  22 - 28 meters
M. cavernosa (males): 1830 - 2127 (many)
M. cavernosa (females):  2123 - 2138 (few)
M. franksi:  2140 - 2214 (many)
D. strigosa:  2200 (few)
S. intersepta (males):  2250 (few)
Sea state:  calm, seas less than 2 feet
Percentage of colonies spawning:   For M. franksi, approximately 30% of
the colonies appeared active.  For other species, it was 10% or less.

August 19, 2003
West Flower Garden Bank
Species:  Montastrea franksi, Diploria strigosa, Stephanocoenia
intersepta.  Non-coral species: Ophioderma rubicundum (ruby
brittlestar), Ophioderma squamosissimum (giant orange brittlestar).
D. strigosa: 2130 - 2220 (many)
M. franksi:  2212 - 2230 (many)
S. intersepta (males): 2252 - 2257 (few)
O. rubicundum:  2045 - 2130 (hundreds)
O. squamosissimum:  2045 - 2100 (few)
Sea state:  calm, seas less than 2 feet

August 20, 2003
West Flower Garden Bank
Species:  Colpophyllia natans, Montastrea faveolata.  Non-coral species:
Ophioderma squamosissimum.
C. natans:  2040 - 2110 (few)
M. faveolata:  2300 - 2330 (few)
O. squamosissimum:  2045 - 2115 (many)
Sea state:  calm, seas less than 2 feet

August 21, 2003
East Flower Garden Bank - 27 degrees 54' 32" / 93 degrees 35' 49"
Depth:  21 - 27 meters
Species:  Colpophyllia natans (many)
Timing:  C. natans:  2045 - 2105
Sea state:  calm, seas less than 1 foot

Other observations:  Significant sponge spawning was observed on the
morning of August 20, commencing about 0915.  Primary participants
appeared to be several cryptic species that encrust on the undersides of
coral ledges, and are interspersed among corals and other organisms.
For that reason, it was difficult to tell what species were involved.
Species identifications are pending.  The output of gametes was high
enough to visibly affect water clarity near the reef.  Signs of spawning
by Ectyoplasia ferox (brown encrusting octopus sponge) were not observed
this year, in contrast to previous years.


G.P. Schmahl
Sanctuary Manager
National Oceanic and Atmospheric Administration

Flower Garden Banks National Marine Sanctuary
1200 Briarcrest Dr., Suite 4000
Bryan, TX   77803

(979) 846-5942
(979) 846-5959 (fax)
george.schmahl at noaa.gov

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