Breathe Deep

The Phoenix Islands "Greatest Hits" highlights continue...

#5: ROV exploration of PIPA depths

Take a deep breath. Go on, try it. In with the good air; out with the bad air. Ahhhhh. It's easy, and feels good, eh? Now, try it underwater. With SCUBA, you can only breathe so deep - around 120 feet on air, if you're a conventional diver. At best, might be able to breathe about 300 feet deep. What about on a submarine? Okay--you can breathe deep there, but you're breathing recycled air. And hence the topic of today's post: since we can't breathe deep underwater (at least not easily), how do we explore deep underwater?

(Left Photo: David Obura) (Right Photo: Jim Stringer)

The answer to this question depends on how deep you want to go. The coral reefs on PIPA are a reef formation known as an atoll (described in an earlier post). One of the features of these mid-ocean, volcanic atolls is that they are basically seamounts that break the surface--so they descend very deep, with a very steep slope. Kiribati is also full of seamounts that do not break the surface. In fact, Kiribati is home to ~4% of the world's seamounts. That's a lot of ocean to explore below the surface!

Seamounts featured between McKean, Rawaka (Phoenix) and Enderbury Islands (Photo: Google Earth)

It would be great to get a manned submersible out to PIPA someday, and hopefully we will soon. But as a first glimpse of the deep, we brought an unmanned ROV with us on this expedition. This ROV (Remotely Operated Vehicle) can only go 500 feet deep, but that's 380 feet deeper than we were diving. And yes--you guessed it--since the ROV was unmanned, breathing was not an issue. :)

Mo preparing to launch the ROV off the boat for a dive (Photo: Larry Madin)

Now, I'm not a stranger to the concept of deep depths. I used to work on deep-sea hydrothermal vents (miles below the ocean!) , but I've never personally journeyed there (though my experiments have). So naturally, I was extremely curious to be on-site for some deep-sea exploration. One of the big advantages of working on these reef atolls with their steep, sloping sides is that we could (and did) literally dangle the ROV out of our ship window (see Mo above with the ROV). Greg could (and did) sit at our dinner table on-ship and drop the ROV below us, while others of us were diving on the reef. As any deep-sea scientist will tell you: what an unlikely (and pleasurable) way to explore! Greg posted extensively on this earlier - see Greg's posts for more photos and details.

Randi Rotjan, David Obura and Les Kaufman look on as Greg Stone controls the ROV (Photo: Larry Madin)

A first glimpse was just enough to leave us breathless (figuratively, of course). Corals living past 300 feet! The crystal clear waters of PIPA were able to allow enough sunlight at depth to support the coral-algal symbiosis. We saw lots of healthy corals, though the diversity was low (just a few species) And fish! Snapper (the same we'd been seeing shallow), and more baby sharks patrolling the slopes. In fact, on one ROV dive, 10 sharks (gray reef and black tip) were seen. And here's the enticing part--when we looked further down the slope at the end of our ROV's tether, we could see that there was more life, still. Breathtaking.

(Photos: Jim Stringer)

Marine organisms are not limited to the shallows the way that humans are. Sadly for us, we have to make the choice between deep breaths or deep depths; we generally can't have both. But ROV's and manned submersibles give us borrowed lungs and enable us to explore the last unexplored frontier--the ocean floor. After all, we know more about the moon that we do about our ocean floor! I'm excited about future ROV and sub explorations of PIPA. After all, the thrilling and mysterious sights of the deep sea will take your breath away--but thanks to this technology, not literally.



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