Like snow falling bottom up – WS Mexico
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“We had a fantastic spawning this night at the La Bocana Chica Reef. Around 10 pm, spawning started nearly everywhere, not just at elkhorn coral colonies where we had set our nets on”, said UNAM scientist Sergio Guendulain Garcia right after the team’s return to the field station. “It felt like snow, falling from below due to the fact that there were millions of gametes rising to the ocean’s surface”, added one of the young investigators. During the night snorkeling, he had witnessed coral spawning for the very first time of this life.
While Sergio started to rinse the team’s diving gear, his colleagues carried two big containers filled with collected eggs and sperm to the UNAM wet lab. There, the contents of both containers were gently mixed together. “We collected these sperm and egg bundles at two different reef sites. Now we are mixing them to get a maximum of genetic recombination and increase the probability of fertilization”, said workshop leader Dr. Anastazia Banaszak.
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All this effort paid off. Eight hours after the mixing, almost up to 100 per cent of the coral eggs had been fertilized. “They are looking bigger now and vary in size and shape”, explains SECORE member Jennie Jansen. She and her team member Barret Christie had started the two SECORE kreisels at night, parenting now approximately 30.000 tiny little embryos in one of the two kreisels.
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Meanwhile, biologist Daniel Gleason from Georgia Southern University made the last adjustments on his experimental setup. He and postdoc Lauren Stefaniak want to investigate, if and how ultraviolet radiation (UV) is changing the embryo’s DNA. That’s why they had worked all night long to select about 4500 freshly fertilized eggs and pipetted them into small containers (15 eggs per container). Now these containers are floating in outdoor tanks, where the eggs are exposed to the daily amount of sunlight. “We are going to take samples every afternoon to see whether the structure of their genetic code has changed due to UV radiation”, said Daniel Gleason.
His study is one out of 12 experiments, which had been relying on fertilized eggs. When it had turned out that the spawn collected during the second night of spawning did not get fertilized, all of the scientists had looked a little worried. This morning, all signs of nervousness had gone. With bins and kreisels full of growing embryos, the data collection and observations can start. However, the researchers wont have much time to investigate the first part of the elkhorn coral’s lifecycle. 107 hours or 4 days after fertilization, the floating embryos turn into swimming larvae, looking for a rocky spot to settle on. So, it is time to return to the lab and get some work done!
Tonight, the SECORE team is going to join the diving team of the Xcaret Eco Park Mexico to collect elkhorn coral gametes at a reef close to the park. If you want to know whether the corals at this site did spawn as much as their relatives further North at the reefs of Puerto Morelos, stay tuned for our next blog entry.