Update on the Science Lung II


Dr. Patrick Colin

Since earlier in the project, there hasn't been any direct mention of how my "homemade" rebreather, the "Science Lung II" has been doing. I have now done 6 deep dives with the Science Lung II, or SL2, with great success. Except for one "shallow dive" to 220 feet, the other dives have been made to 300-330 feet with bottom times of 10-15 minutes. With decompression, total dive time is 2-2.5 hours. The longest dive so far for me has been 180 minutes, of which the last 30 minutes I just stayed down on oxygen to get more time on the scrubber.

The SL2 is a closed-circuit mixed gas rebreather with electronic control of oxygen partial pressure. The SL2 was designed for use in studies of reef fish reproductive activity in relatively shallow water, the design parameters were for a fully mixed-gas capable electronic unit with 3-4 hour duration on scrubber, oxygen and electrics. While my research needs were primarily for relatively shallow-water use (less than 100 feet), the unit was also designed to be capable, using appropriate inert gases, to as much as 400 feet. The SL2 has no integrated decompression computer, so decompression has to be determined by tables, using depth and time information.

The SL2 has been a long-term interest for me, but I went through a long period of having no research mission for a mixed-gas rebreather. I was originally inspired by the work of Walter Starck and his associates in the late 1960's and early 1970's. I completed my first mixed-gas rebreather (the Science Lung I) in 1978, but did not use it extensively due to unreliable oxygen sensors. In 1989 I renewed my interest in rebreathers and using the lessons learned from my original unit, designed the SL2 to specifically meet my needs. The unit is constructed primarily of molded fiberglass and PVC plastic with a chest-mounted counter lung. The complete unit ready to dive weighs 47 lbs and is streamlined, neutrally buoyant and statically neutral in sea water. It is not intended for commercial development or production; strictly for my own scientific research. The realities of liability and diver-induced errors make anything beyond that out of the question. For these reasons, no details regarding the unit will be available. With about 20 hours of deep mixed gas and decompression on it now, I feel the unit is reliable (but not yet to be trusted-that is far in the future) and in the right hands can be a tool to do things that would otherwise be impossible.

I have been able to collect quite a number of interesting invertebrates at depth during this project and in combination with those stalwart invertebrate grabbers, John Earle and Rich Pyle, we have found quite a number of new invertebrate taxa. Unfortunately with most invertebrate groups (as opposed to fishes) it is hard to say instantly that some specimen is a new species or whatever. But I have been able to take quite a few high quality 35 mm slides of organisms at depth using the SL2 and a few of these will be shown here in low resolution form.

Photo 1. This crustacean has not yet been identified, but is extremely common at depths between about 250 and 400 feet. The sit on gorgonians and black corals, watching the world (and rebreather divers) go by.

Photo 2. This shrimp was photographed in a cave at 310 feet, and is probably a known species (although we haven't yet been able to put a name on it).

Photo 3. The benthic ctenophore (comb jelly) Lyrocteis imperatoris is often found on small gorgonians and whip corals at 280-300 feet. Surprisingly, no benthic ctenophores are known from shallow waters in Palau, so this was a pleasant and unexpected surprise.

Photo 4. This tiny ahermatypic coral was found under a ledge at 290 feet. We have no identification at present, but the specimen was collected.

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