Blue water diving to study deep-sea jellies in Nikumaroro

Yesterday, Larry Madin, Kate Madin, Alan Dynner, myself and a Fijian crew member named Koroi drove one of NAI'A's diving skiffs four miles off Nikumaroro and came to a stop. Except for a giant frigate bird hovering over above our heads there was nothing else visible part from waves slapping on the side of the skiff.

A NAI'A diving skiff during a previous Phoenix Islands expedition (Photo: David Obura)

"This looks good," Larry said, as we lowered a 150-foot line into the sea and prepared to dive. On this dive we were not going into look at fish or coral, but rather to survey the most abundant multi-cellular organisms on earth: Jellyfish, sihpnonophores, ctenophores and other gelatinous creatures that live in the open ocean water column, also known as the pelagic ocean environment.

You need to be far from shore and far from the seafloor to do this kind of diving, which for obvious reasons is called "Blue Water Diving." At this location, the seafloor was about 10,000 feet below us, making it ideal; we would be free from any local bottom effects, Nikumaroro was so small that it would have no effect on the ocean out this far, and so we could study pelagic invertebrates in PIPA for the first time.

Blue water diving photo from an earlier expedition (Photo: Michael Aw)

The weight at the end of our dive line splashes into the water and takes the rope rapidly down into the water below. I slip in after it and descend to about 20 feet while I wait for the others. The water is blue all around me with flickering shafts of sunlight streaming from the surface. Below the ocean fades to black and for a moment I get a feeling of vertigo when I realize the sea floor is 10,000 feet down. I clip to my safety line, a thin cord that will allow us to swim out into the water, but not get swept away. Soon Larry, Kate and Alan join me, clip in, and we are like a spider web in the water. I stay at the center of the web. My job on this dive is to collect and observe the animals, but also act as safety diver keeping an eye on the other divers, in case their lines come free and they start to drift away, and to keep an eye out for any pelagic sharks that might wander by. On our dive neither event happens.

The Phoenix Islands Protected Area (PIPA) is the largest Marine Protected Area (MPA) in the world. It's the size of the state of California. Most of the attention to PIPA is drawn by the colorful coral reefs that surround each of the eight atolls in PIPA. But the coral reef environment is a tiny fraction of PIPA. By far, more than 99% of the ocean habitat in PIPA consists of the pelagic environment, the place where a vast array of invertebrates live and drift around; also the area where schools of tuna, pods of whales and dolphins, seamounts, deep sea creatures, many of which await discovery. Our blue water dives are a start to understanding these other dimensions of PIPA.

Near the end of our dive I watched Larry drift over to a beautiful 12-inch-long, shimmering translucent creature flat, but wide like a belt. He carefully slips it into his jar; this particular animal is called, "Venus's girdle," but it is similar to many of these pelagic creatures, soft-bodied with no bones, covered in mucus, iridescent. We also collected two other pelagic jellies, one called Pelagia the other Leucothea.

Left to right: Illustration of a Venus's girdle, a Pelagia (photo: Larry Madin, Woods Hole Oceanographic Institution), a Leucothea Pulchra (Photo: p-tlobos.com)

Reefs are important, but the future of research in PIPA will also include more deep sea and pelagic studies so that we can understand all aspects of PIPA's environment.

-Greg Stone, PIPA Expedition Leader

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