July 12, 2009

The Deepest Dive

Assistant Professor of Biology and Environmental Science at CUNY, Baruch College and Reseach Associate, American Museum of Natural History

LITTLE CAYMAN, Cayman Islands | We’re in deep water down here, but more about that in a minute. First, a little about an exploration in shallower depths.

One of the missions of this trip is to develop a technique to measure and assess what we call coral recruitment–how new colonies of coral are established, how much they grow and how quickly. Corals begin with just one polyp setting and dividing into larger coral mounds. What I want to do is quantify and reassess over a number of years how many juveniles in different locations survive to form adult colonies.

Here’s how we’re doing it: Corals possess a unique family of “fluorescent proteins” that can be detected by shining a specific color light on them at night and viewing the light they emit through a filter capable of detecting only their fluoresced light. Our team lays down transects along various parts of the reef during the day, which we photograph with both still and video cameras. At night, we return to the same transects and reassess the coral recruits with the fluorescent method. We can detect single coral polyps, down to 1 millimeter, that would normally be missed. A quick assessment of the data hints that fluorescent monitoring technique is at least 30 percent more accurate at detecting juvenile corals than by standard counting.

Of course, it’s the deep dives that are the focus of this expedition. I’m here with two of the most qualified technical divers on the East Coast: Casey Coy, director of dive operations at the Florida Aquarium, and Rick Gomez, the dive safety officer at the University of Miami. Before their arrival they sent a barge with large canisters of oxygen, hydrogen and helium gas to make their own mix for the expedition.

We’ve spent six days making morning and evening dives to 240 feet (about the deepest we can go for two scientific dives in a day with enough time to decompress between dives) to obtain samples of corals that are found at both depths. We are focusing on two species of coral, Montastraea cavernosa and Agaricia fragilis. I want to see if the deep coral are genetically any different from those found in shallower water, and to test the idea that the deep water might serve as refugia (an area that has not undergone ecological changes occurring elsewhere and provides a habitat for surviving species. Each day, we return from our afternoon dive in the twilight hours and head back to the lab to rinse our gear and begin processing the coral’s DNA and RNA.

The conditions are rough on the south side of Little Cayman, so we needed to go elsewhere for the final dive—at 300 feet the deepest of the expedition. We took a 17-foot boat through a narrow cut in the northern side of the island as Rick and Casey prepared for their most challenging dive of the week. Though they would be at 300 feet for just five minutes, the entire dive would take over three hours because they would need to make stops to decompress during their assent. There is a strong current and during the ascent we noticed that Rick and Casey launched a red air bag to show their location. Rather than fight the current, they decided that the boat would follow their lift bag for the next two and a half hours until they surfaced. When they did, they had in their possession some of the deepest corals ever collected off Little Cayman Island. I’m excited to get back to shore and into the lab to begin the molecular analysis.

Meanwhile, I hope you’ll take a look at the photos and video we’ve been taking down here. Go to the links on the right side of the page and click on Decade of Science on Flickr. The photo thumbnails that have small “Play” buttons in the lower left corner are videos.

And so the expedition comes to a close. I’d like to stay here longer, but I’ll be back soon enough. In January, I’ll be here with a CUNY contingent, teaching a course in tropical reef ecology. Follow the link below for more information and don’t hesitate to contact me if you’re interested!

http://faculty.baruch.cuny.edu/dgruber/Opportunities_files/Winter%202010%20flier.pdf

In the meantime, the next leg of my summer research adventure awaits: After a brief time back at Baruch, I’ll be off again, this time to Israel and dives in the Red Sea. My blog will continue from there—talk to you then!