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In case anyone was wondering where I've been this past month, this should
explain it. Sorry for the wasted bandwidth to those not interested...
Aloha,
Rich
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1995 Papua New Guinea Deep Reef Exploration: Summary Report
by Richard Pyle
I recently returned from a deep reef exploration expedition to the
Milne Bay Province of Papua New Guinea. We spent 15 days diving from the
M.V. "Telita", a diving livaboard owned by Bob and Dinah Halstead. The
ichthyological expedition team consisted of three individuals: Dr. John
"Jack" Randall, John Earle, and myself. Bob Halstead was also closely
involved with our exploratory efforts. Others on the livaboard included
Debbie Gochfeld and Greta Aeby (fellow graduate students in the Department
of Zoology, University of Hawaii), five other divers (most of whom were
avid underwater photographers) and the crew of "Telita". John Earle and I
each used Cis-Lunar MK-4P Closed-Circuit Rebreathers for the majority of our
dives.
Objectives and Summary of Results (listed in order of importance):
Objective #1: Ensure that nobody gets killed or seriously injured.
We accomplished Objective #1.
Objective #2: Assess the value and applicability of closed-
circuit mixed-gas rebreathers for use in deep reef biological exploration
in remote regions. We found the Cis-Lunar rebreathers to be extraordinarily
valuable and applicable to this sort of exploration activity.
Objective #3: Make an initial assessment of the scope of
biodiversity (particularly reef fishes) inhabiting deep reefs in a region
of tremendous shallow water diversity. Although we had no intentions of
conducting full-scale biological exploration on this expedition, we
nevertheless discovered at least 35 new species of reef fishes (one of
which we cannot identify to genus), and observed at least 8 additional
conspicuous new species, as well as dozens of other more cryptic species
which are probably new.
Logistics and Environmental Parameters:
The "Telita" served as an EXCELLENT base of operations. Bob
Halstead is an extremely intelligent individual and a supurb diver, and
his boat and it's crew are absolutely top-notch. The boat had three
industrial oxygen cylinders, two of which were used as a cascade for
filling rebreather oxygen cylinders, and the third was equipped with an
open-circuit surface-supplied regulator system to be used for Open Circuit
Bailout decompression or emergency IWR treatment (we never needed to use
this rig).
The upper 100-150 feet of water was very warm - usually warmer
than 80 degrees F. There was one discernable thermocline usually in the
range of about 100-150 feet, and another around 260-280 feet. Even on
dives that included up to an hour below the deeper thermocline (with
associated decompression), and on days when I spent more than 6 hours in
the water, I was very comfortable wearing only a t-shirt and swim suit (I
left my wetsuit jacket on the rack after the first day). John wore only
his lycra suit - he did not need his wetsuit either.
All deep dives were conducted on vertical reef drop-offs or steep
slopes. In all cases, the reef extended upward to within 10 or 20 feet of
the surface, making it ideal for decompression diving. In addition to a 30
cf open circuit bailout bottle mounted to the rebreather, John and I each
carried an 80 cf stage bottle. We also established a protocol with surface
support to send more tanks and set up the surface supplied oxygen in the
event of an emergency.
The Twilight Zone in this region is absolutely awesome (in the
literal sense). Most of the drop-offs are riddled with caverns. On one
dive I found the entrance to a cave that was at least 30 feet wide and
about 100-150 feet vertically. The top of the entrance was at a depth of
360 feet. I did not penetrate the cave at all, bit it continued back as
far as my light penetrated (the water at this depth was extremely clear),
and it seemed to "go". There was consitently a small shelf at about 180
feet, and another at about 280 feet, perhaps representing former sea-level
stands. These made for convenient stage bottle stations.
Numbers:
I logged 64 hours on the rebreather over 36 dives during the 15
diving days. My deepest dive was to 420 feet. I made a total of 7 dives
to depths in excess of 300 feet, and an additional 7 dives to depths of
200-300 feet. John Earle logged a total of 32 hours on the rebreather, to
a maximum depth of 333 feet. He made a total of 5 dives in excess of 300
feet and an additional 8 dives in excess of 200 feet. Our total dive times
ranged in duration from about one hour to a little over four hours.
John and I used a combined total of 35 cubic feet of helium (!), a
little less than 300 cubic feet of oxygen, and just over 60 lbs of
Sofnolime for the entire trip (not bad for almost 100 hours of diving,
including 28 trimix dives!)
I shot 27 rolls of film (mostly during decompression) and floded one
Nikonos-III camera with 20-mm lens (stupid mistake on my part).
We travelled on a total of 7 flights with our 422 lbs of gear, and
paid a total of about $700 in excess baggage fees.
Decompression and Oxygen Toxicity:
Because of the diversity of interests of the trip participants,
and because we did not intend this as a full-scale deep reef exploration
project, we avoided committing ourselves to more than 2.5 hours of
required decompression time on any single dive. However, we made at least
one deep dive on all but three of the 15 diving days, and occassionally
made two deep dives in a single day.
All decompression profiles were determined by the on-board
integrated computers of the MK-4P rebreathers. A general modification to
these profiles included additional deep safety stops, and an addtitional
15-45 minutes on pure oxygen at 10 feet (on the rebreather) following
completion of the required decompression (this was not so much intended as
a safety margin, as it was time required to finish shooting a roll of
film).
Our initial plan was to limit ourselves to only one deep dive a
day, and no more than two consecutive days of deep diving. However, we
felt so remarkably good after each deep dive (absolutely no fatigue) that
we decided on several occasions to conduct both a morning and an afternoon
deep dive. With one exception, we experienced no DCI symptoms during the
trip. The exception involved a dive I made with an hour-long bottom time
at 250 feet, in a very strong current (heavy exertion), as the first dive
of the day. I got a bit disoriented during the ascent (wasn't sure how
much to compensate for the current in returning to the boat), and omitted
my usual deep safety stops. Fearing that the other trip members might be
angry that I was holding them up, I did not include any additional time on
oxygen at 10 feet beyond what was required. In retrospect, these
decisions were extremely stupid (cutting out the safety margins on a
high-workload, long bottom-tim deep dive), but at the time we were
beginning to suspect that the decompression profiles generated by the
computer were overly conservative, considering how energetic we felt after
even the longest decompression dives. About an hour after surfacing, I
felt an extremely slight (barely detectable) twinge in my right shoulder.
I'm not even sure it was really DCI (I used that arm alot in fighting the
current).
Otherwise, John and I were amazed at how "alive" (for lack of a
better word) we felt after the deep dives. John is the most experienced
deep diver I know, and I have a fair amount of deep diving experience
myself. For both of us, a certain level of post-dive fatigue is a normal
part of decompression diving. However, day after day we were continually
baffled by the fact that we felt exactly the same way after surfacing from
a 3-4 hour decompression dive as we felt before getting in the water. Even
on days when we spent as much as 6 hours in the water (with no wetsuits),
we were awake and alert and engaged in intellectual/philosophical
discussions with other trip participants late into the night. On one day,
after a deep trimix dive and a long surface interval, John conducted an
air scuba dive with a short bounce to 50 feet, and most of the dive in
less than 25 feet. After the scuba dive he felt slightly tired (the way
he used to feel after all his decompression dives), and went for a third
dive with the rebreather. After the third dive, he felt great again.
Our PO2 setpoint on the rebreather dives was routinely 1.4 ata for
both bottom and decompression. With such long and repeated exposures at
consistently high PO2, we were obviously concerned about oxygen toxicity.
At no time during the expedition did we detect even the most subtle
symptoms of pulmonary oxygen toxicity. On certain dives, a full face mask
was used in conjuction with the rebreather to mitigate the consequences of
an O2-induced convulsion. In retrospect, I believe that our risk of CNS
oxygen toxicity was well within the bounds of acceptible risk.
Conclusions:
By far the most frieghtening experience of the trip was when our
small prop-plane from Port Moresby to Alotau (Telita's home port) was
unable to accomodate the weight of all of our gear. My heart sunk as I
stared out the small window at our boxes containing $100,000 worth of
Cis-Lunar rebreathers sitting on the tarmac, as the little plane taxied
down the runway. Fortunately, all of our gear made it on the next flight
later the same day, and the world was again a beautiful place.
The most remarkable thing John and I learned about rebreather
diving during this trip was the magnitude of differences in diving
parameters due to individual metabolic variability. For example, one
canister charge of Sofnolime lasted about 5-6 hours for John, and 11-12
hours for me (a two- fold difference), even when exposed to similar or
identical workloads. Similarly, John went through oxygen about twice as
fast as I did, and John always had more condensation forming in his
breathing loop than I did. These differences were very consistent. A
profound consequence of this metabolic difference between John and I is
that I have a much larger margin for error in the event of a failure in
the O2 control system. On a test with a disabled oxygen control system, my
PO2 dropped from 1.4 to 1.0 over the course of about 20 minutes (just
burning the oxygen in one loop volume). At an identical workload, John's
PO2 dropped from 1.4 to 0.5 in less than 10 minutes. I now firmly believe
that all rebreather divers should learn their own metabolic
characteristics under different workloads, and how those characteristics
influence relative points of concern for different rebreather designs.
We all felt this trip was a resounding success, and we are anxious
to return for more serious exploration with Cis-Lunar MK-5P rebreathers next
year.
End of Report
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