What Do Las Vegas and Coral Reefs Have in Common?

Coral Reefs: The Las Vegas of the Sea (Credit: Patrick Cooney)
Dirty Little Secret
I will let you in on a dirty little secret of mine: I am not a fish biologist.  I study corals.  Unlike fish, corals do not migrate, they do not school, and last I checked, they aren’t even delicious.  Putting it that way, corals sound awfully boring and unimportant.
Take one dive on a coral reef, and I bet ‘boring’ won’t cross your mind. (Source)
Is there a Sin Reef? 
Quite the opposite of actually being boring, what if I told you that coral reefs are teaming with life and have a lot in common with Las Vegas?  After all, coral reefs are where fish go to let loose, stay up all night, eat at massive 24 hour buffets, and of course, look for that opportunity to make new fish.  Just like you know all about your local town’s watering hole, much is known about shallow coral reef habitats, but up until recently, crazy tales of what looked like giant fish parties were all anyone hinted at when talking about deep water coral reefs.
Lots of flare on the reef and in Vegas. (Source)
What Happened to the Sun?
Some of your favorite reef fish – the groupers and snappers that taste so delicious – leave the comfort of their local watering holes and swim long distances to gather with others in trendy deep water locales along the edges of continental shelves in search of a good time and a mate.  These gatherings are called spawning aggregations, and at times, schools of these enthusiastic and hopeful fish are so dense, they blot out the sun.
All that is missing is the velvet rope and disco lights. (Source)
Joining the Party
For humans, these deep water habitats where spawning aggregations occur are pretty tough to get to, as they are often many miles offshore, the locations are mostly unknown, and they can be at depths greater than 200 feet.  Divers on SCUBA traditionally had a tough time (read as “died”) spending any useful amount of time at these depths, making ‘what happened at the reef stay at the reef‘…until recently, with the advent of mixed-gas diving and rebreathers.  With this new technology, researchers can now get 10-20 minutes of time at 150 feet with reasonable confidence we won’t kill ourselves in the process.
Descending and ascending take up a majority of time when diving deep. (Photo: Dan Holstein)
That Coral is a Perfect 10!
Recently in the US Virgin Islands, when researchers first started visiting these grouper and snapper spawning sites, they were amazed by what they found.  Not just huge randy fish, but coral!  Lots and lots of coral – some of the best looking coral in the Caribbean.  These habitats were so different from traditionally studied reefs that they were even assigned a new name: Mesophotic coral reefs (meso-, meaning middle or intermediate, and –photic, meaning light).  Approaching the reef is like watching the giant buildings of Vegas rise up out of the barren landscape.
The Secret is Out
The secret is out on these congregating dog snapper and Nassau grouper, as we now know many of these particularly remarkable spots they have been selecting for their courtship.  Researchers are clamoring to learn more about how these newly discovered habitats tick and why fish so heavily select them as breeding grounds.  Further, as more and more shallow coral reefs disappear, it is possible that all we (and the fish) will be left with are these deeper reefs that may serve as refuge to those looking for habitat.  With this understanding, it is imperative that these habitats be conserved for long term preservation.
A well thought out plan is necessary to conduct research at these depths. (Photo: Dan Holstein)
Can You Protect What You Didn’t Know You Had?
In a happy confluence of good management and serendipity, many governments – including that of the US Virgin Islands – are moving to protect fish spawning aggregations, and in doing so, they are inadvertently protecting a benthic habitat and resource they did not even know they had.  Now it is my job (and the job of many other fantastic researchers) to study how and why these corals and associated organisms have done so well in these unknown areas, and what we can expect in a changing and uncertain future.
Only recently have we discovered these beautifully intact deep water reefs. (Photo: Mark Vermeij)
Fish Love = Coral Conservation
So, while I may not be a fish biologist, I am thankful that fish feel the strong urge to leave their homes and travel to the middle of nowhere, all for a chance at love; Otherwise we may not be paying attention or conserving these fascinating habitats.
-Dan Holstein
About the author
Dan Holstein, the guest author of this post, is a PhD candidate at the Rosenstiel School of Marine and Atmospheric Science, University of Miami, Florida.  His research investigates the roles of deeper coral reef habitats in a changing climate.  He can be contacted at dholstein@rsmas.miami.edu.
Dan Holstein, Coral Biologist by day, Coral Reef Entertainer by night
Further reading:
Armstrong, R., Singh, H., Torres, J., Nemeth, R., Can, a, Roman, C., Eustice, R., et al. (2006). Characterizing the deep insular shelf coral reef habitat of the Hind Bank marine conservation district (US Virgin Islands) using the Seabed autonomous underwater vehicle. Continental Shelf Research, 26(2), 194-205. doi:10.1016/j.csr.2005.10.004
Lesser, M. P., Slattery, M., & Leichter, J. J. (2009). Ecology of mesophotic coral reefs. Journal of Experimental Marine Biology and Ecology, 375(1-2), 1-8. doi:10.1016/j.jembe.2009.05.009
Nemeth, R. S. (2005). Population characteristics of a recovering US Virgin Islands red hind spawning aggregation following protection. Marine ecology progress series, 286, 81-97.
Smith, T. B., Nemeth, R. S., Blondeau, J., Calnan, J. M., Kadison, E., & Herzlieb, S. (2008). Assessing coral reef health across onshore to offshore stress gradients in the US Virgin Islands. Marine pollution bulletin, 56(12), 1983-91. doi:10.1016/j.marpolbul.2008.08.015
Smith, T. B., Blondeau, J., Nemeth, R. S., Pittman, S. J., Calnan, J. M., Kadison, E., & Gass, J. (2009). Benthic structure and cryptic mortality in a Caribbean mesophotic coral reef bank system, the Hind Bank Marine Conservation District, U.S. Virgin Islands. Coral Reefs, 29(2), 289-308. doi:10.1007/s00338-009-0575-8
Whiteman, E. A., Jennings, C. A., & Nemeth, R. S. (2005). Sex structure and potential female fecundity in a Epinephelus guttatus spawning aggregation: applying ultrasonic imaging. Journal of Fish Biology, 66, 983-995. doi:10.1111/j.1095-8649.2005.00653.x

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