SPAWNING, SPAWNING, & MORE SPAWNING!
Most stony corals found in the Florida Keys grow very slowly. They are sessile animals, meaning they do not move and are attached to the rocky substrate of the reef. But just like every other animal, each individual has a different genetic makeup. So how do they reproduce and pass on their genes? Every year, a few days after the first full moon in August, our corals start feeling a little bit romantic. With warm waters and calm seas, stony corals like staghorn and elkhorn coral have this opportunity to reproduce only once a year.
When the time is right, which is sometime around 9:30-11pm, the coral prepare to release sperm and egg bundles. This preparation is called “setting”. The bundles are brought up into the mouths of the polyps and sit there as the coral prepares to release them. This can be identified by a small orange-ish bulge at the mouth of the polyps.
Staghorn coral, Acropora cervicornis, setting its egg/sperm bundles in preparation of spawning. © Andrew Ibarra/Coral Restoration Foundation™
Once the coral colony feels that it is ready, it will start releasing these buoyant gamete bundles into the water column. They slowly float up towards the surface and eventually break down into sperm and egg. At this point, it is up to fate and the ocean currents to determine whether they mix with gametes from a different coral and produce a brand new, genetically distinct baby coral.
Staghorn coral in the CRF™ Tavernier Nursery preparing to spawn. ©Alex Neufeld/Coral Restoration Foundation™
So, in this edition of Talking Science, we're excited to share the incredible work that has been conducted the past month regarding this year’s spawning season. This season, we wanted to do something we have never done before. We know that corals in our nursery have been spawning for a few years, and we know we have outplants that are now thriving and mature enough to spawn. But we asked, “Do our outplanted corals spawn? And, if so, are there any differences in the timing and frequency of spawning in the nursery corals vs the outplanted corals in the wild?”
We conducted a series of observations in both our Tavernier Nursery and at an outplant site in northern Key Largo named North Dry Rocks, which has lots of large, successful staghorn outplants from previous years. In addition, we called in some help from our friends over at the South-East Zoo Alliance for Reproduction and Conservation (SEZARC). They assisted us in conducting an operation which involves collecting the released sperm and egg bundles and preserving them with a method called cryopreservation. Let’s take a deeper look into each event.
The CRF™ team prepares tents over coral colonies in the CRF™ Tavernier Nursery. © Alex Neufeld/Coral Restoration Foundation™
North Dry Rocks (NDR)
Our team of scientific divers went out to North Dry Rocks (NDR) to observe whether certain genotype clusters would spawn. On the night of August 6, 2020 we saw something never seen before. We witnessed 14-month-old staghorn corals, propagated and outplanted by CRF™, spawning in the wild on Florida’s Barrier Reef Tract. These are the youngest CRF™ nursery-raised, outplanted staghorn corals to be observed spawning in the wild. In fact, they may be the youngest staghorn corals EVER to be observed spawning in the Florida Keys!
“We were all so excited when we surfaced back up to the boat. I personally never thought I'd have the opportunity to witness coral spawning in the Florida Keys. It's an incredible feeling to know that I'm one of the few people in the world that observed what may be the youngest outplanted staghorn clusters ever to spawn. It gives me hope for the future of our reef ecosystems," said Andrew Ibarra, CRF™ Lead Intern.
Not only did we see spawning, but we saw a lot of spawning. CRF™ outplant clusters are mono-genetic, meaning that each one is made up of multiple corals of only one genotype. During our nightly surveys, we watched several clusters of multiple genotypes and saw many of them spawning! This shows that not only one genetic strand that is succeeding, there are several.
Elkhorn spawning. © Coral Restoration Foundation™
However, we can't let the staghorn take all the spotlight. There was another monumental spawning occurrence that occurred just 1 day prior. On August 5, Dana Williams, an Associate Scientist at University of Miami, took a team out to monitor both naturally wild and CRF™ outplanted elkhorn corals, and they witnessed the CRF™ outplanted elkhorn coral spawning on the Florida Barrier Reef Tract!
This was the first time ever that elkhorn coral outplanted by CRF™ was observed spawning.
Outplanted in 2015, Williams’s team successfully collected and cross-fertilized 2 genotypes. These new genets will be housed at the University of Miami for the time being. Unfortunately, none of the wild elkhorn colonies that were being observed spawned that night at NDR. But despite this, it tells us that our corals are healthy and thriving and have taken that step to help repopulate the reefs.
While those 14-month-old staghorn corals were spawning at North Dry Rocks, the same thing was happening a few miles away in the world's largest coral nursery. The CRF™ Tavernier Nursery is home to over 500 Coral trees. CRF™ Science Program Manager Amelia Moura and Science Program Intern Krista Laforest selected 25 genotypes to be fragmented from the Coral Trees and hung up in “Spawning Alley”, which is the area of the nursery dedicated to observing spawning. Spawning Alley was set up in 10 rows of 3 trees, where each cluster was hung on a mini tree branch like shown below.
Staghorn colonies hung on mini branches used for spawning observations in Tavernier Nursery and staghorn spawning on a tree in the CRF™ Tavernier Nursery. © Alex Neufeld/Coral Restoration Foundation™
We put these clusters onto these arms for a couple reasons: it provides a better and more efficient layout to monitor corals, but more importantly, it gives our team enough space to tent our corals. What do we mean by tents? They're essentially mesh nets that we place over the entire mini branch. The tents are made out of a very fine mesh and have a test tube attached to the very top. They help collect the egg and sperm bundles once the coral releases them. As they are naturally buoyant, the bundles simply float up into the test tube.
Our team of staff and interns dove the nursery for 7 nights, monitoring, observing, and recording data about when the corals start to set and spawn. We found that this subset of colonies spawned for 7 days in a row! This marks another new record for CRF’s coral spawning season, as this is the most nights in a row we’ve ever watched our nursery staghorn corals spawn. Of course, not every cluster spawned every single night. Differences in genotype spawning frequencies were observed and it will be interesting to see what questions this may answer (or bring up) about the reproductive behavior of our nursery corals.
CRF™ Dive Training Administrator Roxane Boonstra holds collected coral gamete bundles inside of a test tube. © Alex Neufeld/Coral Restoration Foundation™
What's even more exciting is that all of these genotypes have not been witnessed spawning in the past. CRF’s nursery contains over 120 genotypes of staghorn alone, so each year we can only watch a small subset. This year, we focused on ones not used in past years’ spawning efforts. These are all new genotypes that were sexually mature! So we now have all these gametes from new genotypes collected. What happens with them? Keep on reading to find out!
With the help from our friends at the South-East Zoo Alliance for Reproduction and Conservation (SEZARC), who have been working with us since 2015, we collected gametes to be frozen and preserved through a process called cryopreservation. Cryopreservation is a method that can be used to preserve organs, tissues, cells, and yes, even coral gametes.
SEZARC Research Lab Manager Cayman Adams explains cryopreservation during night 2 of spawning season with CRF™. © Coral Restoration Foundation™/South-East Zoological Alliance for Reproduction and Conservation Research
Only the sperm portion of the bundle can be cryopreserved, so SEZARC takes the sperm and cools it with liquid nitrogen to a temperature of -196 degrees Celsius. This stops any natural chemical activity that could break down the biological material without harming the gametes with ice crystal formation. This year, with SEZARC’s help, we were able to cryopreserve sperm from genotypes never preserved before. These efforts are essentially creating another genetic ark of corals on land, ensuring that we do not lose genetic diversity as CRF™ continues with its mission of restoring the coral reef ecosystem.
Left: Coral embryos that have reached the multicellular phase and have begun to transition into the cornflake stage of embryo development. Right: Close-up of coral sperm. © Cayman Adams/South-East Zoological Alliance for Reproduction and Conservation Research
Although the corals have stopped spawning for the year, that doesn't mean the work has stopped. There is still a lot of data to be analyzed and baby elkhorn corals to monitor!
LESS THAN ONE WEEK LEFT TO CELEBRATE!
The Coralpalooza™ Digital 2020 event platform closes in 1 week! And to wrap up our celebration, we’re bringing back the Coralpalooza™ treasure hunt!
Explore our virtual platform and watch the exclusive content to collect as many points as possible. Snag enough points to get yourself to the top of the leaderboard, and win a 10% off voucher to our online gift shop, ReStore Coral.
The Coralpalooza™ Digital 2020 platforms closes on Tuesday, August 25, 2020, so don’t wait! Register for free or log on again to join us here.
"Talking Science" Editorial Intern
Andrew was raised in West Palm Beach, Florida and spent many hours in the Atlantic Ocean swimming
and snorkeling as a child. He graduated from Florida State University with a Bachelor of Science in Environmental Science and minors in biology and mathematics. In school, he researched marine gastropods and conducted sea turtle tagging surveys. After graduating, Andrew wanted to dive (no pun intended) into the world of marine conservation and do something to make a tangible difference for the ocean. After completing 50 dives in the Upper Keys and witnessing ghastly coral graveyards, struggling ecosystems, and degraded portions of the Florida Barrier Reef, Andrew was inspired to apply to CRF™ to actively help restore our beloved marine ecosystem. He is super excited to join the CRF™ family and learn a variety of skills both above and below the surface. In his spare time, Andrew loves playing any and all sports and watching Marvel movies on repeat.