Establishing a Captive Population of Caribbean Acroporids

[OUsnakebyte]

Hello all -

 

 

 

My apoogies for delaying this post.  I've been trying to find time, as I knew it would be a lengthy, likely multiple post thread.

 

 

As many of you know, I originally started with SECORE in Puerto Rico to help establish the beginnings of a live, captive population of Caribbean Acroporids - Elkhorn (Acropora palmata) and Staghorn (Acropora cervicornis) corals.  These corals are currently listed as threatened with extinction and will llikley be downgraded to endangered very soon (they have declined approximately 80-90% throughout their Caribbean and tropical western Atlantic range over the past 30 years. 

 

 

Today, zoos and aquariums serve as live genetic repositories for threatened and endangered species around the world, and the organisms maintained in these populations are educational ambassadors to their wild counterparts.  With the well-documented decline in Caribbean coral populations and the subsequent addition of Elkhorn coral (Acropora palmata) and Staghorn coral (Acropora cervicornis) to the Endangered Species List, it is imperative that zoos and aquariums help these struggling coral communities in much the same way that they aid declining mammal, bird, reptile, amphibian, plant, etc. populations.

 

 

Today, we (US and Europe zoos and aquariums) have Puerto Rican Elkhorn coral in captivity and a minimal amount of Staghorn coral from Florida (the hybrid, Acropora prolifera, is not represented in captivity); we also have cryogenically frozen genetic samples of Elkhorn and Staghorn corals from Puerto Rico and Belize in gene banks.  However, we need to diversify our captive genetic diversity.  SECORE has moved to working on a reef restoration project in the Caribbean island of Curacao.  As an offshoot, I have been traveling to Belize the past few summers during coral spawning season, trying to expand the genetic diversity of captive Caribbean acroporids we currently maintain in public aquaria.  The Smithsonian has a field station on the tiny island of Carrie Bow Cay, part of the Mesoamerican Barrier Reef system, off the mainland coast of Belize.

 

This field station is ideal for our project for many reasons, as it has all the flowing seawater, solar power, diving needs, etc. and the corals are located right off the house reef.  Most of the costs are covered by the Smithsonain Marine Science Network - one only needs to get himself/herself to Belize from Washington, D.C.  This is where WAMAS comes in.  Funding for this project was generously provided by the WAMAS Grant Program.  This grant allowed airfare for me to get to Belize and back with these corals and supplies I need to make this project happen.  The following post(s) will detail my 2013 field season.

 

All photos in this thread, unless otherwise stated, are courtesy of Abby Wood.  http://abois.zenfolio.com/f154771040

 

Here is a look at the Carrie Bow Cay (CBC) island and marine station from the reef (the hybrid Acropora prolifera) is in the foreground:

 

 

 

Another shot of the island - it is small enough that you can walk the perimeter in 5 minutes, at a leisurely stroll (no kidding).  The amount of scientific papers per square foot that come from research on this island is pretty astonishing.

 

 

I'll continue this year's field season in subsequent posts.

 

Cheers

 

Mike

 

[OUsnakebyte]

Our field really season began in January 2013 when Abby Wood (photographer and NZP volunteer) and I traveled to Carrie Bow Cay (CBC) to begin the conditioning of our coral recruit settlement tiles.  In addition to placing the tiles in seawater six to seven months in advance to “cure,” we also implemented a new strategy – harvesting a known preferred settlement cue, the crustose coralline algae (CCA) Hydrolithon boergesenii from the reef – and gluing it to our settlement tiles.

 

 

 

 

The grids of tiles were then secured in two pvc/mesh crates and tied to the reef in two locations – one on the CBC house reef and the other in the lagoon area on the east side of the island.  This was done with the hope that a known settlement cue – the CCA Hydrolithon – would have a “head start” and grow on/encrust our settlement tiles to make those tiles an “ideal” location for larval coral settlement.  Upon our return to CBC this July, we found that in many cases the Hydrolithon had taken hold and began encrusting our tiles.  However, the tiles placed in the lagoon area east of the island had a much higher rate of turf algae coverage (these coral larvae often avoid turf algae).  If this experiment is repeated again, both crates will likely be placed on the CBC house reef or on the reef wall.

 

 

 

 

 

 

 

This year, the full moon (and anticipated possible early spawn) had us returning to CBC for the Acroporid spawn in late July.  At day five after the full moon, we finally collected our first samples of Elkhorn larvae.  Night six saw more Elkhorn spawning and collection, with very minimal Staghorn.  Since the Staghorn bundles were from the same clone (the same genotype), none of these larvae survived; however, Staghorn eggs were crossed with Elkhorn sperm that night to create larvae of the hybrid, Fused Staghorn Coral (A. prolifera).  Four days after fertilization, the larvae from the two species were placed in separate settlement bins with the tiles from the reef, and approximately 2,000 Elkhorn and 300 Fused Staghorn larvae settled.

 

 

A. palmata setting (holding egg/sperm bundles prior to spawning release):

 

 

 

A. palmata releasing egg/sperm bundles:

 

 

 

 

 

While the corals are setting, we place nets over portions of the colonies to capture samples of the bundles.  The key is to get as many different genotypes as possible:

 

 

 

 

 

[OUsnakebyte]

After we get the bundles back to the lab, it's time to mix boys and girls together.  We all know what that gets us... BABIES!

 

The bundles are separated, and the pink eggs float to the top while the sperm is in the container below:

 

 

We have to mix eggs of one colony with sperm of another colony, as Elkhorn coral has a very low self-fertilization rate.  Staghorn will self up to about 20%, but the larvae typically are not very fit.

 

 

 

 

 

 

As hybrids fascinate me, we also took some of the Cervicornis eggs and crossed them with the Palmata sperm to make the hybrid A. prolifera.  This cross has a better fertilization rate than the reverse.

 

 

Fertilization probably happens almost immediately, but we leave them in the tri-pour containers for an hour for fertilization.  After about an hour has passed (and things have settled down from the chaos that is working a coral spawn...), we transfer the eggs to our flow-through holding system. The CBC wet lab has a flow-through seawater system in which a pump brings in fresh seawater from the reef, thus eliminating the need for constant water changes.

 

One thing the SECORE team has done for the past several years is to design a system for holding large amounts of larvae that will "stir" the larvae in a circular tank for several days during development.  If the larvae "clump up" for too long, they typically perish.  Each "kreisel" you see is held in a plastic trash can that has 5 water stream inputs - four around the top and an upwelling from the bottom.  Despite the various water inputs to each tank, it is still necessary to manually stir the larvae to separate them from clumping.

 

 

 

 

 

 

 

The next morning, it's time to check fertilization rates (success).  On a good spawn with healthy, motile sperm, it is not uncommon to get 90% or more fertilization success.  Fertilization is easily scored by counting a small sample of each kreisel.  By the next morning, unfertilized eggs will still be round while those that are fertilized will now be flattened down into the very scientifically-named "cornflake stage." 

 

 

 

 

 

 

After this, it's time to just let the kreisels work, stir the larvae, and let them develop for about 4-5 days.  By day two, the unfertilized eggs have fallen apart and the "unfit" fertilized eggs have died off as well.  After the "cornflake" stage, the fertilized eggs have rounded back out and gone to the new "jelly donut" phase:

 

 

 

 

By day 4 or so, we now have well-developed, swimming larvae.  They go from round to an elongated form, then entering the "baseball bat" or "bowling pin" stage.  These swimming larvae will now begin to swim to the bottom of the holding tanks and look for suitable locations to metamorphose to a primary polyp:

 

 

 

 

 

At this point, the different researchers that have descended upon this tiny island for two weeks during spawning season will utilize the larvae in different experiments (settlement substrates, temperature, bacterial, etc.):

 

 

 

 

 

Up next is settlement of the larvae...

[OUsnakebyte]

When the larvae have reached the swimming phase (typically 4-5 days), it's time to move them from the holding kreisels to settlement bins.  We then place the grids of settlement tiles into different bins and hope that what we have selected for them they also find a suitable home. 

 

 

 

After a few days in settlement, we can then check the tiles on the grids to assess settlement rates.  The larvae settle WITHOUT their endosymbiotic zooxanthellae, so they are a pale white when counted.

 

 

 

Each baby coral is now only about 1mm in diameter and VERY delicate.  It never ceases to amaze me that these behemoth, SUV-sized colonies of Elkhorn corals that are remaining on reefs in the Caribbean today started their lives - 150-200 years ago - as these tiny, milllimeter-sized single polyps.

 

One thing we think *might* help post-settlement survivability is this aggregate settlement.  It seems that when two or more larvae settle next to one another, they will often fuse, forming a chimera.  This "joining forces" it seems might allow them to grow faster than if only an individual polyp and get a head start on forming a new colony.

 

 

 

 

 

Sadly, the juveniles experience upwards of 90% or more mortality in the first three months post settlement in captivity - so the majority of these won't survive.  This is why we need to bring back THOUSANDS to try to ensure that we have some remaining in the months to come.

 

After the corals have settled in for a few days, now comes the most stressful time of the entire trip.  As if diving and working around an endangered species (trying to touch it as little as possible), working day and night caring for thousands and thousands of endangered coral larvae for a week, and just trying not to screw up is not enough... now we have to transport about 1700 settlement tiles back to the zoo in Washington, DC - all in one long... stressful... day.

 

We start around 4:30am packing up the settlement grids into two coolers.

 

 

 

The trip back to DC will begin at 7am with a 45 minute boat ride back to mainland Belize, and then a pond-hopper plane flight from Dangriga to Belize City to board a flight at 11:30am to Miami.  After clearing customs with all the appropriate CITES export and FWS import permits, we fly from Miami to DC, arriving at the zoo around 10pm, where we start acclimating the corals - whcih takes about 3 hours to complete.  Assuming no luggage has been lost, coolers haven't leaked, and nothing has been seized at customs, I call the day a win.

 

After the corals are back at the Invertebrate Exhibit in D.C., we then have to get the zooxanthellae to the polyps.  Since most corals in the genus Acropora are spawned without their zoox, we have to provide it for them.  While back at the field station on Carrie Bow, I have also taken the time to centrifuge down some of the zooxanthellae.  I put the grids into tanks with water that just barely covers the tiles and add the zoox to the tanks.  These corals will then ingest the zoox through the mouth, where it is stored throughout the polyp.  Once we see brown speckles in the otherwise pale white corals, it's nice to know that photosynthesis is now occurring within their tissues.

 

 

 

The grids and corals are now being kept in holding tanks at the Invertebrate Exhibit at the Smithsonian's National Zoo:

 

 

 

 

In the months to come, I will slowly, individually, look at all the tiles in the tanks to assess any remaining survivors.  This year we were only able to bring back Elkhorn coral (Acropora palmata) and some of the hybrid (Acropora prolifera) back to the exhibit.  Sadly, there was a disease outbreak ravaging the Staghorn coral (Acropora cervicornis) on the house reef at Carrie Bow, and these corals only spawned very minimally.  Thus, there were no Staghorn larvae to work with this year.

 

I want to once again thank WAMAS and their grant program for the continued support of this project.  Every bit of funding we can get for this project helps.  I fund myself for this project from completely outside sources - the zoo currently does not have the funds to contribute to this project (they and my wonderful coworkers do support me with time away from work, however).  When we consider what corals do for the ecosystem they build and how important they are to the world's reefs (and economies), they deserve our attention. 

 

Many thanks once again to Abby Wood for use of her photos.  Documentation for a project like this is extremely important, as it is difficult to tell in words what a picture can easily describe for us.  I only used a small portion of her photos.  More from this trip and others can be found here:

 

http://abois.zenfolio.com/carriebow

 

Finally, this is an active and open thread.  If anyone has questions or comments, I'll be happy to respond.

 

Thanks again.

 

Cheers

Mike

 

[OUsnakebyte]

This is pretty cool, seems like a good project to fund. Are there any plans afoot to have you come to a meeting and talk about the research there...with some equipment show/tell/explain?

 

Yes, I would absolutely give this talk at a meeting if wanted.  Most of my supplies stay on Carrie Bow at the station (to reduce shipping costs), but I might have a kreisel around here I could bring...

 

Cheers

Mike

[Origami]

Sadly, the juveniles experience upwards of 90% or more mortality in the first three months post settlement in captivity - so the majority of these won't survive.  This is why we need to bring back THOUSANDS to try to ensure that we have some remaining in the months to come.

 

 

First of all, Mike, thanks for such a captivating start to this thread! Many thanks to Abby, too, for her great photos without which the story would not be as clear or intriguing.

 

Regarding the juvenile mortality rate: Is there knowledge of the survival rate in the wild for juvenile at 3 months? Is it comparable to the 90%+ that you see under controlled conditions? What is being done to understand this high mortality rate and to perhaps raise yields?

 

Please let us know also how the CCA-encrusted tiles performed relative to past settlement substrates as the assessment progresses.

 

Finally, thanks for all of your hard work on this!

[YHSublime]

I am taking this all in, as I have just finished reading. That's absolutely amazing, and a bummer about the Staghorn.

[matt]

Yes, I would absolutely give this talk at a meeting if wanted.  Most of my supplies stay on Carrie Bow at the station (to reduce shipping costs), but I might have a kreisel around here I could bring...

 

Cheers

Mike

 

Mike - I think this would be a great follow-up talk since we're having Copps talk about SPS success this time. I don't call the shots, but if I was voting I would say "aye" to you giving a talk at the next meeting.

 

It would be nice to get the whole she-bang in a presentation, but after absorbing some of this info I'm keying in on something small and specific from a simple hobbyiest perspective with captive coral. Such as you do with coral larvae, how might a hobbyist isolate desireable zoanthella and possibly re-introduce it to bleached/recovering corals? Is that something that really works best at the larval stage or could most smallish sized corals (frags maybe) be aided if disease doesn't interfere? And or course, how can I get my acros to spawn????

[Origami]

Mike - I think this would be a great follow-up talk since we're having Copps talk about SPS success this time. I don't call the shots, but if I was voting I would say "aye" to you giving a talk at the next meeting.

Great story here and would love to hear more. We've actually already arranged for the Winter meeting speaker, though. (Stay tuned.) We try to stay a little ahead of the curve and to make sure that we get on speakers' calendars as early as is reasonable. Copps is our speaker coordinator. So if you  have specific requests, run them by him and/or the officers.

[TheyCallMeMr.703]

This is really cool.

[OUsnakebyte]

Regarding the juvenile mortality rate: Is there knowledge of the survival rate in the wild for juvenile at 3 months? Is it comparable to the 90%+ that you see under controlled conditions? What is being done to understand this high mortality rate and to perhaps raise yields?

 

Please let us know also how the CCA-encrusted tiles performed relative to past settlement substrates as the assessment progresses.

 

Finally, thanks for all of your hard work on this!

 

We don't know what mortality rates of the larvae are in the wild, but it is likely even greater than in captivity, given the greater competition and predation pressures.

 

We've tried various things - higher densities, lower densities, feeding with different regimes (types of foods and frequency).  I really don't know what we could do to raise our yields.  It is worth noting that after 3 months, survivability tends to level out.

 

 

In the past, we have on had settlement rates of around 6-10%.  In one bin (a low density settlement bin), we had about 15% settlement.

 

This was the first year we tried to get the tiles in the seawater in advance with the CCA on them.  The problems lies in competition of various CCAs.  My colleagues at the SI marine station in Ft. Pierce, Fl have spent years determining which CCAs will induce settlement and which will inhibit settlement.  Get the right CCA, and the larvae will flock to it.  Get the wrong one, and the larvae will avoid it.  The CCA we collected was all hydrolithon (each piece ID'd under a microscope prior to gluing), but... upon getting the tiles off the reef this summer, other CCA had settled on the tiles, competing with the Hydrolithon.

 

 

 

It would be nice to get the whole she-bang in a presentation, but after absorbing some of this info I'm keying in on something small and specific from a simple hobbyiest perspective with captive coral. Such as you do with coral larvae, how might a hobbyist isolate desireable zoanthella and possibly re-introduce it to bleached/recovering corals? Is that something that really works best at the larval stage or could most smallish sized corals (frags maybe) be aided if disease doesn't interfere? And or course, how can I get my acros to spawn????

 

Well, if you have a coral that has bleached, it is likely that there might still be some zoox remaining in the coral.  As you know, if environmental conditions are remedied, then there is usually sufficient zoox remaining in the coral that can divide and recolonize.  However, if you wished to sacrifice a healthy adult coral to try and reintroduce zoox to a bleached one, you would need to crush up a part of the coral with a mortar and pestle, place the bleached frag in a very small amount of water and add the crushed coral water to the bleached frag and let it sit there for... about an hour.  

 

However, if there are other, healthy corals in the tank there is likely sufficient zoox in the water column already.

 

Re getting captive acros to spawn reliably and predictably... replicate the long-term seasonal temperature fluctuations, the lunar cycle, sunrise and sunset, proper nutrition and perhaps even some sort of pheromone-like chemical in the water.  Oh, and you'll also need a minimum colony size, which is usually (not always) too large for our small tanks...  

 

Cheers

Mike

[smallreef]

Very informative, and hopefully, with long term intervention like yours these colonies will not only be widely seen at places like the Smithsonian, but back in the reefs.

[lutz123]

Fascinating! Thanks for giving me something new to learn about.

[londonloco]

Very interesting......

[dave w]

You and SECORE are doing fantastic work to pioneer these methods.  I hope one day that sexually propagated corals can supplement or replace cuttings.  Until that day comes, thank you for doing so much hard work.