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percent, while on the control reefs stony coral cover declined
25 percent. The density of juvenile stony coral colonies, an
indicator of the success of coral reproduction, increased 151
percent on the experimental reefs and only 55 percent on
the control reefs. Crustose coralline algae, which promote
settlement and survival of coral larvae, increased 160 percent
on the experimental reefs and less than 1 percent on the
control reefs. Brown macro algae that fight with coral for light
and space decreased on the experimental reefs by 45 percent
and increased on the control reefs by 31 percent.
This study empirically and emphatically demonstrated it is
possible to restore Diadema to a Florida Keys coral reef, and
that restoration can reverse the decline of coral and decrease
the macro algae that shroud the reefs.
Culturing DiaDema
Diadema are still present on the reefs of the Keys but in
such small numbers they are not ecologically functional.
A female Diadema can produce 15 million eggs at each
spawning, but she must be close to a male for reproduction
to succeed. Thus, if enough Diadema can be maintained
on a reef to keep it clear of macro algae, the coral would
benefit greatly and the urchins could spawn effectively. All
that must be done is to develop the technology for hatchery
culture of Diadema and then create a scientific program to
establish and maintain functional populations on specific
reefs. Surely this is not an impossible task, and justifiable if
it can result in the restoration and protection of the Keys’
coral reef ecosystem, a true national treasure.
Spawning
I kept a brood stock of 20 to 35 adult Diadema in a 200-
gallon saltwater system in my lab for more than four years.
I found that simply placing adult urchins in a container of
warm water stimulated them to spawn if they were ready.
This process made it possible to spawn them whenever a
rearing run was scheduled.
larvae rearing
Rearing Diadema larvae is more difficult than rearing the
larvae of other sea urchins. Diadema larvae are among the
smallest urchin larvae, and they have a long planktonic life.
Metamorphosis from a planktonic larva into juvenile urchin
may occur as early as 36 days but may take several months.
The larvae require slow-moving water similar to oceanic
currents as well as open-ocean water quality, making it
difficult to maintain laboratory conditions necessary for their
growth and development. Successful culture to mature larvae
and metamorphosis into the early juvenile stage was routinely
accomplished in my small laboratory; and although survival
into stable, feeding juveniles was problematic, the basic
spawning and larvae-rearing technology had been developed.
In the spring of 2011 the project entered its second phase
and was transferred to Dave Vaughan at the Mote Marine
Laboratory’s Tropical Research Lab (TRL) on Summerland
Key. Vaughan is working with large-volume larvae-rearing
tanks, successfully conducting post-metamorphosis feeding and
producing many more viable juveniles. Beginning with the work
at Tom Capo’s University of Miami laboratory and continuing
with my work at my small lab and Vaughan’s work at Mote
TRL, the project is now moving ahead toward juvenile urchin
behavior studies and research in the placement and survival
of Diadema on reefs. I am confident it will soon be possible to
start the next phase of research: developing successful methods
of restoring and maintaining functional populations of this
critical herbivore on the coral reefs of the Keys.
AD
learn MOre:
This research was made possible by funding from the Protect
Our Reefs specialty license plate program sponsored by Mote
Marine Laboratory. With continued funding and support, Diadema
may soon return to the reefs of the Florida Keys. You can sup-
port Diadema restoration by visiting www.mote.org to volunteer,
purchase the specialty plate (Florida residents) or make a dona-
tion. Will Keys reefs ever return to the 50 percent coral cover
seen in the 1970s? That might be a stretch in our lifetimes, but
with more Diadema on the reefs, coral restoration efforts by
Ken Nedimyer’s team and the water-quality improvements from
sewer installations replacing septic tanks, scientists are fighting
the good fight.
T I M GRO L L I MUND
T I M GRO L L I MUND
COUR T E S Y MO T E MA R I N E L A B
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