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Advancing Diving Technology

NOAA's Undersea Research Program SCUBA dives to greater depths to study invasive lionfish

By Taylor Sisk

The primary objective of the National Oceanic and Atmospheric Administration's Undersea Research Program (NURP) is putting research scientists into the water. NURP supports the technology needs of scientists who work underwater to research and resolve important national and regional environmental problems. This effort takes a number of forms, including the use of autonomous underwater vehicles (AUVs), human-occupied submersibles and remotely operated vehicles (ROVs), to go beyond the limits of scuba diving. But many ecosystems are within reach of conventional and advanced scuba diving technologies, ecosystems of substantial importance to our nation's coastal economies.

Coral reefs - rich hard-bottom communities that support abundant fish populations - and extensive sand plains that hold buried resources - scallops, for example - are among the places NURP scientists regularly dive.

While technology has brought forth many impressive advances in the technology employed to understand the oceans, diving remains a critical component of undersea research.

Indeed, says Steven Miller, former director of the Southeast U.S. and Gulf of Mexico NURP Center (SEGM) at the University of North Carolina at Wilmington, "Most scientists will tell you there's nothing better than putting brains and hands underwater to conduct research - as opposed to cameras and robotic arms."

Paula Whitfield will certainly tell you as much. Whitfield is a fishery biologist at the NOAA Center for Coastal Fisheries and Habitat Research, and this past summer headed a three-week NURP-supported dive to assess the status and potential risks of a lionfish invasion into Atlantic waters. Whitfield and her colleagues dove from the R/V Cape Fear off the coast of North Carolina at locations where they believe lionfish are over-wintering.

In the past four years, the Indo-Pacific lionfish, Pterois volitans, has made a home for itself, reproducing and dispersing off the coast of the southeastern U.S., from Florida to Cape Hatteras and Bermuda. It's believed to be the first Pacific marine fish to populate these Atlantic waters, and is, in Whitfield's words, a decidedly "ostentatious" presence out there.

Whitfield has been diving off the coast of North Carolina for 14 years. She first became aware there were lionfish out there in August of 2000. "But I didn't really take it very seriously," she says, "till the following summer; that's when a lot more reports started coming in from divers. I started tracking their position based on the reports, which were coming in from as much as 60 miles apart. I knew then we were on to something.

"It was such a huge shock that they were here," so far from home.

"They're probably the most ostentatious fish out there, so flashy and different. When you see them in the Pacific, they seem to belong. But when you see them here, it's like, 'what are they doing here?' There's really nothing else that has their color characteristics and their pectoral fins - and the way they flare them, they almost look like feathers; that's how people describe them."

No one knows for certain how they arrived. But given that they're popular aquarium fish, Whitfield believes they were most likely unintentionally introduced from aquariums from somewhere along the Southeast U.S. coast.

Whitfield and her colleagues are targeting locations where they believe the lionfish are over-wintering, and hence might be spawning. "We can then get a better idea of their total population, or at least an estimate of their abundance at these different sites."

Whitfield acknowledges the role ROVs play in lionfish research - searching for lionfish in habitats that are too deep for divers to reach, for example. But, once having located densities of lionfish, "we'll begin making collections, which is really the tricky part - and which can only be done by divers. I'm not aware of any ROV that could actually catch a lionfish. I know they've tried, but the technology isn't quite there yet."

Divers can also get into nooks and crannies inaccessible to ROVs, thus providing a more thorough assessment. In general, Whitfield avows, "You get an insight that only a hands-on experience can give you."

****

Like Whitfield, Steven Miller acknowledges the importance of having access to a variety of technologies - the right tool for the right job. "Beyond the limits of scuba diving, scientists want to ride in submersibles, and, except for the expense, submersibles are typically preferred over unmanned vehicles or robots. Robots are cheaper than submersibles, they have great capability, and human life isn't put at risk when diving deeply.

"But if the depths aren't too great, scientists want to use conventional diving to do their work. There's just something about our species that compels us to explore, to push the limits, and robots don't offer the same experience as diving or riding in submersibles.

"I've used a number of systems, and I can tell you that I prefer to look for myself, touch and feel my samples when appropriate, and get the bigger picture that you just can't sense from behind a camera."

For nearly 30 years, NURP - and its predecessors, the Manned Undersea Science and Technology Program (MUS&T) and the Office of Undersea Research (OUR) - has played a central role in the development and practice of scientific-diving capabilities, including advances in the practice of "technical" diving, using scuba gear and advanced breathing-gas mixtures that combine oxygen, helium and nitrogen, known as "trimix." Technical-diving techniques provide a safe means of extending maximum depths and increasing bottom time; they also limit the effects of nitrogen narcosis and reduce the risk of decompression illness.

This bodes well for the ocean sciences.

"The increase from 120 to 300 feet in depth that technical diving affords," Shepard explains, "doubles the amount of the U.S. continental shelf that we can reach, including critical habitat for many important commercial and recreational fish and invertebrate species.

"Dive technology has improved in two key areas - equipment and procedures. Equipment such as closed-circuit rebreathers were at one time only used by the U.S. Navy. Scientific divers tried them frequently over the past two decades, but they have been difficult to use and had technical problems - you don't want to mess around with your life-support unit. Recently they've benefited from computer developments and from debugging that comes with time."

In fact, NURP is along the leading edge in advances in rebreather technology.

Derek Smith is dive officer at NURP's Caribbean Marine Research Center (CMRC), where rebreathing exercises are being actively pursued.

"It's kind of a strange thing," says Smith, "because rebreathers have been around longer than regular open-circuit scuba; they've been around since the 1800s. We're talking crazy old breathing helmets and all that kind of stuff. Since then, rebreathers were being used commercially. But they never came to the forefront of the scientific diving community, except for with a select group of people who were trained to use them and had unlimited checkbooks with which to gain access to the equipment and to the training."

"But now there are more and better rebreathers being manufactured and marketed," Smith says. "One of the biggest pushes in scientific diving right now is bringing rebreathers to the scientific communities. Although their cost per unit is relatively high, once you own one, the cost per dive is phenomenally low."

The manner of diving Captain Jacques-Yves Cousteau introduced to the world is called open-circuit scuba and uses compressed gas and a breathing regulator. A lot of the gas is wasted in this process, more and more the deeper you dive. Rebreathers employ a breathing loop that recycles the gas.

"Rebreather technology is computer controlled and it can keep your partial pressure of oxygen at a very set level," Smith explains, "whereas with trimix you might need six different mixtures of gas to get yourself to different depths, and they're either worn on the divers themselves or sent down on a line. You have to keep switching gases to make sure you're breathing the right amount of oxygen at different depths.

"But a rebreather can be computer controlled such that it keeps the oxygen at the exact right place you want it no matter what depth you're at."

Smith says the gas-management capability of rebreathers is impressive.

"Eight dollars of helium, for example, can be stretched in a rebreather over many, many dives.

"Most people think of rebreathers in terms of deep and long dives," says Smith. "You can do long-duration dives at great depths with a lot fewer decompression obligations. But we're also talking about using rebreathers in perhaps ten feet of water." The advantage here is nearly unlimited bottom time without having to change tanks and the absence of bubbles, which can affect fish behavior.

"When you're down there," says Whitfield of her lionfish dives, "the last thing you want to do is be making a racket with all those bubbles. You can just see it changing the fish's, and all the other organisms', behavior. It just changes everything. I think if we weren't making all that noise, we'd be able to observe a lot more. Some of the animals are attracted to you, but then others aren't, they have aversive reactions. So you could minimize those kinds of behavioral issues with rebreathers, which is especially important if you want to go down and conduct a census and not scare everything in sight."

There is, however, good reason for moving forward with rebreathers in a cautious manner, says Miller. "People are still dying using rebreathers. Yes; people sometimes die using conventional diving techniques too. But rebreathers have had a bad reputation for many years, as people were dying because they either maintained or used the equipment wrong, or the equipment failed. For this reason, NURP is working to ensure that rebreathers used for scientific purposes meet safety guidelines and that scientists are properly trained in their usage

"NURP is about providing technology in an extremely safe operational environment. Marine scientists, after all, shouldn't have to risk their lives when they go to work. Rebreathers are still in the test phase, but may soon be routinely used in scientific diving."

Smith says CMRC will be conducting rebreather classes, and will do comparisons between trimix and rebreather diving techniques - "not only between gas usage but also decompression obligations.

"We'll be having the same divers doing the same dive profiles on the same projects but utilizing these two different modes of diving. So in addition to actually getting research itself done - which is going to be collecting sponges, looking at chemical compounds for natural-products research, like cancer therapy - the kind of thing that's now coined as 'bio-prospecting' - we'll also be conducting analyses of diving techniques."

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As for today, NURP is helping facilitate a great deal of very productive work in the 150- to 300-foot depth range.

Paula Whitfield's, for example.

There are a number of compelling reasons for learning more about the invasion of the lionfish. They have no known natural predators in these Atlantic waters, and feed quite ravenously on commercially important fish species, including snapper and grouper. They also have neurotoxins that can paralyze other fish.

Whitfield points out that very little research has been conducted that directly examines the impact of a marine fish in an open marine system, and that this research will serve as an important step toward understanding the consequences of marine fish invasions in general. NOAA has recently identified invasive species as one of the top five stressors in coastal regions - along with pollution, climate change, extreme events, and land and resource use.

In preparation for her summer 2004 lionfish dives, Whitfield trained with NURP in the Florida Keys, learning, for example, how to use three different gas mixes on any one dive and how to decompress under a variety of circumstances, such as free floating in the water column. Her next step will be to become trimix certified, so as to get down to 200 feet, important, inasmuch as, "We're finding more and more evidence that the lionfish are deeper [than we've thus far been looking]. Depending on what we find through our surveys - if there does appear to be a lot of them at the deeper sites - it's going to really drive our research deeper.

"Diving is always going to be an important component anytime you want to make collections like this. I get a lot of pressure from people saying, 'Why aren't you just using ROVs?' ROVs can't do everything; you have to get down there yourself and take a good look at the system."

For more information:

http://www.noaanews.noaa.gov/stories2004/s2264.htm
http://www.uncw.edu/nurc/research/spotlight_on.htm
http://shrimp.ccfhrb.noaa.gov/lionfish/mission.html

[10/18/04]

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