[Coral-List] Diadema culture
martin_moe at yahoo.com
Thu Jun 25 21:18:45 EDT 2009
To coral list on Diadema Culture
I am encouraged! Over the last 3 years I have been working
intensively to develop a process for the mass culture of the long-spined sea
urchin, Diadema antillarum, the key
herbivore of the tropical western Atlantic coral reefs. As you know, before the
plague of 1983, this urchin maintained the ecological balance between coral
growth and macro algae growth on our Atlantic reefs and also conditioned the
limestone substrates to better accept settlement of coral and other
invertebrates. Ecological restoration of western Atlantic coral reefs depends
in large measure on the return of Diadema in ecologically functional numbers. This may/should eventually occur naturally
as pioneer populations increase and expand, but natural restoration has been limited
and spotty over the last 29 years.
If we could produce large numbers of healthy juvenile Diadema in hatcheries in a variety of
sizes and ages, with appropriate genetic background and high health, and learn
to stock them responsibly and effectively (see www.StockEnhancement.org), it would
be an exceptional tool for research and development projects for ecological
restoration on selected coral reef areas. In fact, it may be the only effective
biological tool available for ecological restoration of Atlantic coral reefs.
Now the lack of herbivory is by no means the only difficulties these reefs are
facing, but the return of ecologically functional herbivory will certainly help
the corals of the western tropical Atlantic in
their battle to survive and thrive. In Florida, the great ecological, economic, and environmental
value of our coral reefs to our communities, State, and nation, estimated at
6.3 billion dollars in sales and income and more than 71,000 jobs annually,
demands that we follow every real and potential pathway toward restoration of
the health of our coral reefs. But Diadema are very difficult to rear, especially in mass culture. The major bottlenecks
to mass culture that have been encountered in the past have been their long
larval phase, which exceeds 30 days, and their delicate physical structure,
which is easily damaged by conventional rearing techniques.
However, over the last three years, with the tangible and
intangible support and encouragement of Mote Marine Laboratory, specifically
Drs. Kevan Main, David Vaughan, and Ken Leber, through the Protect Our Reefs
license plate fund grants, and the support and collaboration of Tom Capo and
his staff at the University of Miami, we have made significant progress in the
mass culture of larval Diadema. The
following has been accomplished:
Collection and maintenance of two brood stocks of adult Diadema, about 50 at Tom Capo’s lab at
UM and 19 in my small lab in the Florida Keys at Islamorada. The brood stock urchins in my lab have been maintained for 3
years with repeated spawning and minimal mortality.
Development of a technique for non-invasive spawning of Diadema, pretty much on demand,
including egg collection and incubation. 15 million good eggs have been produced in each of the last two spawnings.
Development in my little lab of a technique for maintenance
and growth of relatively large volume cultures of micro
algae for several months with simple procedures.
Development of 50 liter culture vessels and techniques that
support and grow large numbers of Diadema larvae, 1 per ml, about 50,000 per culture vessel over 50 plus days (whatever
is necessary) to the point of competency for metamorphosis. These culture
vessels provide the patterns of water movement that keep the larvae in
suspension while avoiding excessive turbulence that prevents normal growth and
development of the larvae. The operation of the culture vessels is also very
adjustable so that the variable requirements of the larvae over the span of
culture can be met.
Discovery of the biological cues that stimulate rudiment
development and competency for metamorphosis, and subsequently induce the
process of metamorphosis in the larvae. This aspect of the culture process is
still highly speculative, more definitive work is needed to identify and
quantify the most active biochemical elements, a process beyond my capability,
but in general, a workable method seems to have been established.
A method that separates competent larvae with external
rudiments and tube feet that are ready to settle from larvae that are still in development is being
tested and apparently functions adequately.
Successful larvae culture is the major breakthrough of this culture project. At this point, culture day 50, thousands of larvae are on
the cusp of metamorphosis with large rudiments and hundreds are apparently in
the early juvenile stage. (I say apparently since once the metamorphosing
larvae are in a settlement environment of rocks and algae they cannot be easily
observed until they have attained a size of 3 to 5 mm test diameter. However,
small representative samples of larvae transforming into early juveniles indicate
that metamorphosis to a significant degree is successful in the large settlement tanks.) The next steps in
the development of this technology are to determine the best methods for
settlement and early juvenile growth and survival, and to develop methods for
growout of the juveniles to the sizes that might be required for restoration
purposes. Successful replication of this rearing technique at other locations will also be a part of the next steps.
Although there is much to be done before large numbers of
reef competent Diadema are available,
the basic process has now been developed; it is not perfect, there is a lot of
room for improvement and refinement in every area, but the essential workable
fundamentals have been established. The reason for my post is simply to alert
you that the basics for this technology are being developed and we are
encouraged by recent breakthroughs. And if one old, retired marine biologist
can do this by himself in a makeshift marine laboratory in a spare room on a
very limited budget, well then, it can be done wherever science meets the sea.
It will take a while to figure out how to get this initial work prepared for
publication and actually published, but time is of the essence and it is
important to begin to think about and plan how large numbers of Diadema can be produced and utilized in
coral reef research and restoration projects.
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