Two words can sum up the November 2011 coral spawning research season on the Great Barrier Reef in Australia—NO DIVING! Or, perhaps, crocodile and jellyfish might be more appropriate. This coral spawning research season had a very different feel from previous excursions—no diving at night, no setting nets to collect coral gamete bundles, no passing bottles of bundles to a snorkel team to rush in to the lab, fresh from the reef. No buzzing zooplankton whizzing around the dive lights, seeing reef squid feeding at night, or watching, and swimming in, that underwater snowstorm that is so characteristic of mass coral spawns of field seasons past.
Saltwater crocodiles that patrol the shores of northeast Queensland, Australia prevent any swimming along the shore. And, perhaps even more painful, and significantly smaller, is the feared Irukanji, a species of box jellyfish. November marks the beginning of the painful Irukanji season, as if dodging crocs wasn’t dangerous enough.
Happily, our colleagues at AIMS, the Australia Institute of Marine Science, have a state-of-the-art marine research facility, complete with temporary coral nursery, flow-through water system, filtered natural seawater (on tap!) and climate-controlled larval-rearing rooms. It is through this magnificent research station (safely away from the crocodiles and box jellies) that we will be conducting our experiments.
Eight Acropora millepora, 8 Acropora tenuis, and 5 Favia favites (brain coral) colonies arrived from the reef on the AIMS ship and were placed in holding troughs on the AIMS campus.
The first night saw 8 colonies of A. millepora spawn wonderfully around 9 p.m., providing all the teams here at AIMS with egg/sperm bundles to kick-start the 2011 Great Barrier Reef spawning season. The Smithsonian and Taronga Conservation Society Australia team (Mary Hagedorn, Ginnie Carter, and Rebecca Spindler) performed some initial sperm cryopreservation experiments, assessed sperm motility for the individual corals, and mixed egg and sperm to perform initial fertilization experiments.
While we did not know it at the time, this would be the one and only A. millepora spawn we would get this season.
With the A. millepora larvae from the previous night developing well, our team dissociated (pulled apart) about 1,000 of the 18-hr larvae to cryopreserve the larval cells. Fluorescent experiments (green cells are alive, red cells are dead) later showed that while some cells did not survive the initial dissociation and cryopreservation process, about half of them did survive and will be cryoprserved and placed into a Frozen Zoo at the Taronga Western Plains Zoo.
On the night of the 14th, a few of the A. tenuis colonies spawned a little, but there was not a large amount of egg/sperm bundles to work with. In addition to Mary Hagedorn, Ginnie Carter (Smithsonian Conservation Biology Institute) and Rebecca Spindler (Taronga Conservation Society Australia), Mike Henley from the Smithsonian National Zoo also joined the team. Since this was now a different coral than the A. millepora that spawned the night before, the team once again assessed sperm motility, mixed egg and sperm for fertilization to develop larvae and cryopreserved the A. tenuis sperm.
However, an important observation was being noticed. It seems that the quality of the sperm from individual coral colonies varies from night to night. Why this is, no one can say for sure, but it is important to begin to collect reliable data to map these trends. This would be a major goal for Tuesday night’s spawn (if any of the corals had any spawn left to give).
The morning was once again spent dissociating (pulling apart) 12-hr and 20-hr larval cells (this time from A. tenuis), cryporeserving them and assessing them for viability post-thaw. The results from A. tenuis proved to be much more promising, with an overwhelming majority of these larval cells surviving the dissociation and cryopreservation process.
Tuesday night = HUGE SPAWN! Six of the Acropora tenuis colonies spawned, releasing TONS of egg/sperm bundles. Cryopreservation of the sperm began immediately. Estimating sperm motility, counting the number of sperm per bundle and the number of eggs per bundle, however, would last well into the night. We were in for a very long night, indeed, finishing up around 3 a.m.
In addition, the sperm from most of the colonies was pooled into one large sample and cryopreserved. This sperm would later be thawed and used to fertilize fresh A. tenuis eggs to demonstrate how cryopreserved sperm techniques could be applied in the future.
Once again, the morning was spent staining dissociated larval cells of A. tenuis and looking under fluorescent microscope to check success rates. And again, happily, the majority of A. tenuis larval cells survived the cryopreservation process, while the others were kept in the cryo-bank.
Wednesday night yielded the last spawning of the A. tenuis colonies, with only 3 colonies spawning. Bundles from colony #5 were collected and analyzed for sperm motility and concentration and number of eggs. Colony number 5 did not spawn the night before, therefore, it was the highest priority from which to sample. Sperm was also sampled and stored via cryopreservation.
The first of the brain coral colonies (F. favites) also spawned this night, however, it was only just a very few bundles; there was just not much to work with. Initial motility was estimated, but that was it for this night of brain coral spawning. We did, however, look at the brain coral spawn 12 hours later and were AMAZED that some of the sperm was still motile and functioning.
Thursday was spent waiting for the brain coral to spawn. Sadly, there was no brain coral spawning this night, despite the colonies appearing as if they would release bundles.
Once again, the day was passed preparing for a massive brain coral spawn. Sadly, however, after waiting until well after 10:30 p.m. and no spawning corals were observed, we decided to call it a night and thus end the 2011 spawning season of Great Barrier Reef corals. It’s unfortunate that the brain corals never spawned, as that would have provided us with a good amount of data to compare sperm motility and concentration assessments and egg numbers across different genera.
But, that’s how corals and coral spawning often goes. It’s like that box of chocolates Forest Gump referenced, you just never know what you are going to geT.
FINALLY! A day off! Saturday was a much-needed day of rest for the team, and we headed off to Magnetic Island to hike the trails and see some of the native Australian flora and fauna. Local celebrity sightings included rainbow lorikeets, sulphur-crested cockatoos, many rock wallabies, and several koalas, two with young at their sides.
It usually takes about a minimum of five days for larval development, and that’s what the larvae were doing the past five days, developing.
Data entry, data entry, and more data entry. One of the necessary evils of science is the absolute need to input your data into a spreadsheet program, and that what much of the day and next day consisted of, data entry.
More data entry and graph analysis. Again, not the ultra-sexy field work and sampling of spawning corals, but certainly no less important. The team also began writing two papers for possible publications, a note for Coral Reefs (the journal) and a submission to Reef Sites.
After a much-needed break from the writing, cryopreserved larval cells from 12 hour and 20 hour A. tenuis were given to an AIMS researcher to see if they can be grown, even just a few days or weeks, some time in the near future. If this is successful, it will be a HUGE step forward for the knowledge of coral cryopreservation and larval cell development.
Settlement experiments are starting to get set up and take place. One exciting experiment getting set up and running is the use of A. tenuis larvae that were fertilized with cryopreserved and thawed sperm. About 3,000 such larvae were created last week, and if these larvae can prove to settle, metamorphose and grow, it will also be a major jump in defining the success and merit of cryopreservation as a conservation technique for corals and coral reefs in the future.
Update! The A. tenuis larvae that were produced from cryopreserved sperm did successfully settle and metamorphose to primary polyps, or, a baby coral. The next step in the process to determine if cryopreservation can be further used as a conservation tool is to see if these corals can continue to grow, and eventually sexually reproduce as mature colonies. Of course, that will likely take a minimum of 5 to 10 years to discover, so… STAY TUNED!