杏吧原创

AQUARIUS has been described as the space station of the deep. In reality it
looks more like a large metal box covered in seaweed. But like its celestial
counterpart, it is kitted out with all the gear you need to survive in an alien
environment. There鈥檚 the breathing apparatus, freeze-dried food, rudimentary
sanitation and, of course, communications equipment. Aquanauts are monitored 24
hours a day by 鈥渕ission control鈥�. Wherever you go on Aquarius, cameras seem to
be watching you.

Back in July, when I stayed for a week, privacy was really at a premium. Not
only were we being filmed by a crew from National Geographic, but there was also
live video broadcast continuously on the Internet. My wife checked on me each
morning while she and I both had our coffee鈥攕he sitting comfortably in our
study, and me wrapped in a towel sitting on a bench in Aquarius next to shiny
steel machinery, radios, compressed gas valves and lines, and five other guys in
need of a shave. As an aquanaut, you grow used to the cameras, and I鈥檓 sure
there were moments of opportunity for voyeurs, especially during the mad rush to
get dressed each morning for our dives.

The constant attention did have a positive side, though. One of my tasks at
the New England Aquarium in Boston is to interest people in the wet bits of our
planet. We know more about outer space than about the deep oceans that cover
two-thirds of the Earth鈥檚 surface. More people have walked on the Moon than have
visited the deepest part of the ocean, and even marine scientists have few
chances to immerse themselves in field research. We spend most of our time at
computers or in the lab analysing data collected from distant locations by other
people or even by robots, satellites and other automated systems. It鈥檚 important
work, but if we are to understand the marine environment, we must also go into
the sea with our own onboard computers鈥攐ur brain鈥攁nd our own
biological sensors鈥攕ight, hearing and touch. That is why Aquarius is so
crucial.

Nowadays, Aquarius is the only research 鈥渉abitat鈥� where scientists can live
and work in relative comfort on the seafloor, but the history of living under
the sea stretches back several decades and includes over sixty habitats with
names such as Hydrolab, Helgoland, Klobouk and Subigloo. Back in the 1960s, NASA
became convinced that the psychological problems of living under the sea would
be the same as those experienced during an extended space flight. So it teamed
up with the US Navy to launch the US Tektite habitat programme鈥攏amed after
the small meteorites that survive the fiery plunge into the sea and come to rest
on the seafloor. As part of the programme, aquanauts spent up to 60 days on the
ocean floor鈥攖he predicted length of future space missions at that
time.

But as the space programme accelerated and grew, the undersea programmes
faltered and shrank. Gone are the visions of undersea cities, mineral
extraction, exploration of the seafloor and armies of aquanauts conducting
research. The disproportionate fascination with space compared with our interest
in the sea is best illustrated by the statistic that the cost of one space
shuttle mission could fund the Aquarius undersea laboratory for 500 years.

Our boat left in the afternoon. It took us past million-dollar homes along
the waterways of the Florida Keys, before entering the open ocean just east of
Key Largo. Sixteen kilometres out, we stopped above Aquarius. There we donned
our gear, sat on the dive platform and were pushed headfirst into the water with
our 75-kilogram air tanks on our backs. Now the previous week of rigorous
training came into play. As we descended our minds raced, recalling the special
procedures for saturation diving and the advice about how to cope with our
oversized tanks, buoyancy compensators and emergency gear. Goodbye Sun, goodbye
being dry, goodbye privacy鈥攚e were headed for our new home on the
seafloor.

It was choppy at the surface, but as we swam down below the waves the water
became calm and we were bathed in the beautiful blue light of a tropical coral
reef. Just ahead we could see the large yellow shape of Aquarius. Covered with
corals and seaweeds, it looked much older and more worn than the shiny object
I鈥檇 seen in pictures taken while Aquarius was in dry dock last year. The 12 by
2.5 metre metal box attracted many animals and appeared to be part of the reef
itself. We saw nurse sharks, large rays, moray eels and three enormous tarpons
circling the habitat as if they were the rightful owners.

High-pressure living

You enter Aquarius through the wetporch, a door in the floor. It works on the
same principle as an inverted glass immersed in liquid. Because the air pressure
inside is equal to the sea pressure outside, water cannot get in. Once inside,
you鈥檙e breathing normal air, but at the ambient pressure of the ocean. For every
11 metres you descend, the weight of the ocean above you equals the weight of
the entire atmosphere pushing down on you. So 18 metres below, we were
experiencing two and a half times the pressure of normal surface living. This
would be our storage depth for the next week.

After 24 hours in this high-pressure world, the tissues in our body were
saturated with increased concentrations of gases. Once saturated, you can spend
as long as you want diving at your storage depth and make very long excursions
to deeper waters below鈥攐verall more than quadrupling your diving time
compared to surface divers. You also feel high all the time, like you just drank
a martini. It鈥檚 a side effect of breathing compressed air called nitrogen
narcosis, sometimes referred to as 鈥渕artini鈥檚 law鈥�. No one knows why, but the
increased level of nitrogen in the air you breathe enters the blood and affects
the brain.

The record for saturation diving is around 500 metres, and lab animals have
been saturated and decompressed to the equivalent of over 1300 metres. But even
at 18 metres, saturation diving is among the most dangerous and challenging
diving that exists. Whenever you saturate the human body with air at a pressure
other than one atmosphere, there is the potential for decompression sickness or
the bends. It happens to astronauts as well as scuba divers. Everyone is
different, there is relatively little data and unexpected things can happen. But
one thing is clear鈥攊f you surface too quickly while saturated it can be
fatal.

The dissolved gases in your tissue and blood emerge as bubbles, disrupting
nerves and blocking blood flow. Your blood and tissue will foam like a shaken
bottle of soda. So you must spend hours decompressing before you can safely join
the world above. For us, the decompression time was 17 hours, which puts you a
long way from the nearest hospital if anything should go wrong. On top of all
this, aquanauts are exposed to the usual dangers of scuba diving鈥攅quipment
failure, unpredictable currents and fatigue鈥攃ompounded by long excursion
times and the deeper depths we dive to.

The aim of this particular mission was to investigate coral growth. I was
asked to join the team by Steven Miller, director of the Aquarius programme at
the University of North Carolina at Wilmington, who was looking for a marine
scientist who could speak Japanese. This was the first US-Japanese project in
Aquarius, with the research led by my colleague Mineo Okamoto from the Japan
Marine Science and Technology Center in Yokosuka.

Over the past few years Okamoto and his team have been taking repeated
measurements of coral productivity and biomass in different parts of the
Pacific, and the Aquarius mission was their first opportunity to extend the
research into the Atlantic. They use underwater isolation chambers and
respirometers to measure primary production and gas exchange. Understanding how
reefs grow and the part they play in the global carbon cycle is critical to
understanding how they affect the ocean鈥檚 chemistry and their role in global
climate change. Today over 10 per cent of the world鈥檚 corals are dead or dying,
and human activities such as burning fossil fuels, coastal development and
harvesting corals are mostly to blame. What particularly interests me about
Okamoto鈥檚 research is that it should highlight the importance of conserving the
corals we have left and trying to restore those that have been lost.

On the first evening we made an exploratory dive to a place called the Ridge,
a coral outcrop about 400 metres southeast of Aquarius. Everything was going
according to plan. At about 6 pm my New England Aquarium colleague Ken Mallory
and I re-entered Aquarius and began preparing dinner. The habitat is well
stocked with freeze-dried foods which are delicious鈥攁fter a three-hour
dive almost anything salty, sweet or spicy tastes good. Inside it felt hot and
humid as we rinsed off the salt water and stored our gear. Looking around at the
other aquanauts, all of us now inside our air-filled cylinder on the seafloor,
made me realise how small and warm the space was.

And it got hotter, and hotter. Within two hours the temperature was 35 掳C
with a relative humidity of 95 per cent. This was not normal鈥攖he air
conditioning system had failed. Suddenly we were conducting an unplanned
experiment to see what happens when you put six people inside a small container,
under pressure and then let things heat up. It was unbearable. With the air
already very thick from the high pressure and now heavily laden with water
vapour, it became almost impossible to breathe. Even the martini-high from the
nitrogen was not enough to make the situation funny or pleasant.

By this stage in the mission, we were well on our way to being saturated and
could not surface without 17 hours of decompression. We were trapped in a
claustrophobic steam bath with no hope of a quick escape. The habitat looked
like the morning after a big party: bodies lying on the floor or draped out of
bunks, while our resident technicians, Jay Styron and Clifford Rassweiler, tried
to fix the problem.

At midnight, after the technicians were unable to pinpoint the fault, mission
control came to the rescue. Charging out across the water in speedboats, they
arrived like the cavalry and worked on the 20-tonne life support buoy floating
above us until they found the problem鈥攁n air lock in the coolant line.
Within two hours we were back to a comfortable 24.5 掳C and 78 per cent
humidity. Our first night on Aquarius had been more than we had bargained for,
but the quick response from mission control left us in no doubt that we were in
capable hands.

When there are no system failures鈥攁nd despite our experience they are
rare鈥攖he biggest problems aquanauts face are ear infections and skin
rashes from the constant immersion in water, the noise from the machinery inside
the habitat and personality conflicts from living in such close quarters.
Mostly, life on the seafloor is too hectic to worry about such irritations. And
in the moments we did have between eating, diving and sleeping, we would
entertain ourselves by reading, sending e-mails and surfing the Internet.

My favourite pastime was simply to gaze out of the porthole in the main
cabin. Along with the sounds of radios, air circulators and pneumatic doors,
there was the soft, muffled crackling of shrimp and feeding fish outside on the
hull of the habitat. A soft blue light filtered in from the reef and disappeared
into the mist of water between 20 and 30 metres away. Fish would swim by the
porthole, pause to look at me, and then swim on.

One evening at around midnight we were diving with the National Geographic
film crew. We had been placing pieces of coral in isolation chambers to measure
the night respiration of the coral animals. Afterwards, we Aquarius residents
swam quickly back into the relative comfort of our home. Realising that the film
crew faced a long journey to their own beds, we decided to send them off in
style. Some music, perhaps, taken off the Internet and played to them through
speakers outside the habitat.

As the film crew swam up to the surface in the inky blackness of the ocean,
they were surrounded by the ominous 鈥淏a-dump! Ba-dump! Ba-dump!鈥� of the theme
tune from Jaws.