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Click below to go to the Cruise Logs - (photo credit: Lophelia Coral - Open-File Report 2008-1148 & OCS Study MMS 2008-015)

DISCOVRE 2009



Cruise Log: 9/23/2009    



Deep water corals spawn in the Gulf of Mexico

Sandra Brooke

Scanning electron microscope image of a larva of the deep water coral Oculina varicosa - click to enlarge
Scanning electron microscope image of a larva of the deep water coral Oculina varicosa - click to enlarge
The massive and complex Lophelia coral reefs that we have been exploring during this cruise, started out as tiny planktonic larvae that landed on the seafloor and began to grow into colonies. The larvae, which are called 'planulae' and are about 1mm long, develop in the water column from eggs and sperm released by female and male coral colonies. This method of producing larvae is called broadcast spawning and is very common in the kinds of corals that form large reefs throughout the world. The larvae can swim, but being so small they are mostly at the whim of ocean currents, which may either keep them close to their home reef, or carry them away to different parts of the reef and to new open seafloor. This larval dispersal process is very important since it ensures the reefs are genetically diverse and better able to resist disease and changing environmental conditions.

This is an image taken under a light microscope showing mature eggs packed into a Lophelia polyp - click to enlarge
This is an image taken under a light microscope showing mature eggs packed into a Lophelia polyp - click to enlarge
Scientists know quite a lot about the reproductive cycles of shallow tropical corals, but very little is known for most deep water species. Data from previous cruises indicated that Lophelia should spawn sometime during late September and early October, so for the past few dives we have been collecting samples of Lophelia coral in the hopes that they would release their eggs and sperm, and ultimately produce larvae to study. The cruise was coming to an end and it looked as if we might be out of luck, but this morning when I checked the coral tanks, I noticed the water was cloudy - an indication that the male colony had spawned, and sure enough, there were eggs in there too! This was exciting since it is the first record ever of spawning for Lophelia in US waters. Later this afternoon, a male colony spawned again, and this time we were there to witness the event. The next challenge is to maintain the embryos and larvae through their development so we can begin to learn how long they live, how they behave and how they respond to different environments. There is still much to learn, but this is a great start, and a fantastic end to the cruise.



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