Claire Nouvian
THE DEEP
The extraordinary creatures of the abyss
256pp. University of Chicago Press. $45; distributed in the UK by Wiley.
£23.50.
978 0 226 59566 5
Tony Koslow
THE SILENT DEEP
The discovery, ecology, and conservation of the deep sea
292pp. University of Chicago Press. $35; distributed in the UK by Wiley. £18.
978 0 226 45125 1
In 1968, Howard Sanders, a young scientist at the Woods Hole Oceanographic
Institution, published a paradigm-shifting paper on deep-sea biology. With
careful, analytical study and a heavy weight of data Sanders finally killed
the prevailing theory of the depauperate, species-poor deep sea, and showed
incontrovertibly that the small, mud-dwelling species – mainly polychaete
worms and crustaceans – are actually more diverse in the deep than in
temperate or even tropical shallow-water areas. These data, generated from
what was essentially the first comprehensive but mundane sampling program,
astounded scientists, and even today we speak of “before or after” the
Sanders study.
William Beebe was the first man to descend into the deep sea in the early
1930s, using a highly primitive steel sphere equipped with two fused-quartz
viewing ports, and open trays of soda lime to keep carbon-dioxide levels
low. But without a camera or any means to take samples, Beebe was forced to
recount from memory and his notes the organisms that he observed. The
fantastical bioluminescent displays he reported seeing were considered with
scepticism by most scientists at the time. In 1960, when Jacques Picard and
Don Walsh dived to the bottom of the Mariana Trench at 10,916m, the first
time any vehicle had been to this depth, their dataset consisted of just two
observations – some mud, and what appeared to be a fish.
It is easy to imagine the “real” deep-sea scientists at the time, sceptical of
these new technologies, and busy building up their own picture of the deep
from the time-honoured and highly effective means of fishing trawls or
dredges. But with the benefit of hindsight, we know now that Beebe’s
observation of bioluminescence in the deep midwater was not fanciful, and
that Picard’s fish may in fact be important data, since trawls from the deep
trenches have shown dominance by gelatinous sea cucumbers and an almost
complete absence of bony fish. Furthermore, the technologies that were
developed on the back of these brave explorations have since opened the deep
sea to the full range of high-definition photography. Nowhere is the value
of this new technology better demonstrated than in Claire Nouvian’s
astounding new book The Deep: The extraordinary creatures of the abyss.
In 1998, Craig Smith, an oceanography professor at the University of Hawaii,
had with some difficulty obtained the carcass of a stranded 35-tonne Gray
Whale, towed it out to sea and sunk it in 1,600m of water in the Santa Cruz
Basin. Since that time, he had been making regular visits to the
undersea-whale remains, using whatever deep-sea submersibles were available
– initially, the famous Alvin submersible that found the wreck of the
Titanic, and more recently the remotely operated vehicle Tiburon, owned by
the scientists of the Monterey Bay Aquarium Research Institute (MBARI). I
myself and my collaborator, Thomas Dahlgren, study deep-sea polychaete
worms, and we had been working with Smith for several years on the material
brought up from these whale graveyards.
What we found on these whale remains, named “whale-falls”, astounded us: an
entire novel community of animals, most of them apparently specially adapted
to consuming the remains of whales. As Nouvian points out in her book, a
single whale-fall at the seafloor could represent more food than would
normally be received in 4,000 years, which usually arrives at the deep
seafloor as a “light rain” of organic particles derived from the surface
ocean. One of these specialist organisms, a new genus called Osedax (Latin
for bone-eating) was a polychaete worm that had actually evolved a system of
burrowing roots harbouring unique specialist bacteria that could consume the
whalebone marrow and pass the energy to the worm host. It most closely
resembled the giant tubeworms recorded from hydrothermal vents, and we have
since been developing the theory that whale-falls on the ocean floor may
represent “stepping-stones” for the dispersal of these tiny organisms across
the vast distances of the abyss.
The Deep is far more than an exploration of these strange ecosystems. It is a
remarkable visual tour through the entire deep ocean, with at least half the
book devoted to the “pelagic” realm, the body of water above the deep-sea
floor. With the oceans’ average depth of 3,700m, and covering some 70 per
cent of our planet, this pelagic ocean is by far the largest ecosystem on
the planet, yet also the most poorly known. Although deep-water trawls can
bring up pelagic organisms, the gelatinous nature of them, and rough
handling in the trawl nets, mean that they are almost always damaged.
Although useful scientifically, for DNA sequencing, or anatomical studies,
pictures of trawled jellyfish do not easily inspire. Nouvian, through
collaboration with the Monterey scientists and others, has collated the
world’s first image library of deep pelagic organisms in their natural
environment.
The images astonish. Set against the inky black of the deep, a glowing sucker
octopus Stauroteuthis syrtensis leaps from the page, a pink ballerina
complete with a fairy-light display. A gelatinous siphonophore, a type of
colonial jellyfish, releases a dazzling lightshow of bioluminescence from
its toxic tentacles. Tiburonia granrojo, known to the submersible pilots as
“big red”, an incongruous, metre-wide velvet mushroom-like jelly hangs in
the black, dimensionless deep.
Organisms use light, generated from bioluminescent organs, to signal to each
other, find mates, lure potential prey and confuse their predators. The
deep-water dragonfish has two sets of “headlights”, a high-beam blue light
for searching out prey, and a low-beam red light for signalling to each
other. Because red light is easily absorbed by water, they have also evolved
special red-light sensing organs. Organisms lower down the food chain use
light as a defence, essentially lighting up their predators to larger
predators, most famously in the case of the jelly Atolla, which has a light
display that can be seen over 100m away.
Deep-sea submersibles are, in some ways, remarkably little changed from the
days of Beebe and Picard. There is a small, spherical pressure sphere made
of steel or titanium in which you can just squeeze three people. Three
Plexiglas windows look out on to the sampling gear, cameras and manipulator
arm at the front. The rest of the submersible is composed of batteries,
thrusters and a large amount of uncompressible foam flotation. On a dive to
map and sample deep-water coral communities off the Hawaiian Islands, we
passed through one of the most food-poor parts of the world’s oceans. Blue
is the colour of desert in the oceans, and the central tropical Pacific is
extremely blue. Low nutrients keep the water clear; red and green light is
absorbed by the water molecules, leaving just blue to observe. As we moved
deeper, I observed a thresher shark, Alopias vulpinus, swim past,
distinguished by the long, whip-like fin which is used to stun prey. Beyond
500m, it was dark, and we reached the seafloor, in fact the slope of the
great mountain of Hawaii, at about 700m. Rather alarmingly, a large red
light started flashing in the sub, next to a sign saying “leak alarm”. Our
pilot assured us that this was just a bad connection, and that if the
pressure hull did fail, we would be crushed in milliseconds. The life- support
systems seemed rather basic. Every now and then, Terry, the pilot, would
open a canister of oxygen to top up the air, or open another tray of soda
lime to remove carbon dioxide, just as Beebe did in his bathysphere. There
was a distinct lack of anything remotely high-tech (plasma screens, flashing
lights) – which made sense as the whole sub was powered on batteries with
limited life.
We spent the day using the robotic manipulator arm collecting small pieces of
deep-water corals. The most spectacular, the giant Gerardia gold coral, have
been aged to 300–500 years, and form colonies several metres high. The tiny
polyps (in fact, gold coral is an association of anemones) grow slowly,
filtering the small amounts of food available in the deep-ocean currents of
the Pacific. A fishery for deep-water precious corals started in the 1970s
in Hawaii, using miniature manned submersibles. In other areas of the
world’s oceans, deep-water corals are being systematically destroyed by the
coral fisheries themselves, or as a result of trawlers who find abundant
fish stocks associated with the reefs.
Almost perfectly complementing Claire Nouvian’s book is Tony Koslow’s
excellent study The Silent Deep: The discovery, ecology, and conservation of
the deep sea. Koslow gives a comprehensive history of deep-ocean science, as
well as an overview of the main deep-sea ecosystems. When he writes of human
impacts on the deep sea, Koslow deals a decisive blow to the notion that the
deep sea can ever be immune from unregulated human activities.
In general, Koslow avoids the polemical style, and presents the data as it
stands. The historical review of deep-sea biology is the most comprehensive
I have read, and any reader will enjoy the signature discoveries and rapid
Kuhnian paradigm shifts: the deep sea as a lifeless, dead zone (until
1860s), the deep sea as a reserve of archaic living fossils (1860s–90s), the
deep sea rich in life to its greatest depths, but generally depauperate
compared to shallow water (1890s–1960s), the deep sea rivalling tropical
rainforests for biodiversity (1960s onwards), the deep sea as a habitat for
incredible hydrothermal vent communities, independent of the sun (1977
onwards).
In recent years, studies have estimated that the total species richness of the
deep-sea muds may be greater than 10 million. This is rather a large figure
when one considers that there are only about 1.8 million global species
(both marine and terrestrial) described so far, and that the majority of
those are tropical insects. Rightly, scientists have continued to debate
these figures, which are based on extrapolations from a few square metres of
actual sampling, to the approximately 300 million square kilometres of the
total deep sea. It has been calculated that the total area of the deep sea
that has been quantitatively (that is, carefully) sampled is less than the
size of a football pitch. Tony Koslow dismisses the actual number of species
as insignificant, and perhaps unknowable, but I disagree. Given a large
budget, an appropriate sampling regime such as a series of five,
one-month-long expeditions in each major ocean basin, and a good definition
of what a species actually is, we would be able to provide an answer. The
problem is that we lack an appropriate species definition where grades of
change occur. On one side of the Pacific Ocean, a worm species may appear
subtly different to one on the other side of the Ocean, and populations in
the middle are intermediary. Where does one draw the line in this most open
of ecosystems?
The discovery of hydrothermal vent ecosystems in 1977 changed the face of
oceanography, geology and, perhaps most significantly, biology. The first
expeditions to map and survey underwater vents were led by geologists; when
they brought back two-metre-long, red-plumed tubeworms and giant, sulphurous
clams, they did not even have the chemicals on the ship to preserve them.
Nobody had expected life to survive at this extreme, high-temperature toxic
environment, much less to have adapted to use the chemicals as a basis of an
entire ecosystem independent of photosynthesis and the sun. Biologists now
suspect that the first life forms on earth were formed in vent-like
habitats, and that, if other life does exist in the solar system, it is in
sub-ocean or even subterranean hot vents. If NASA were to scale back its
current spending on orbital space flight, and send instead a series of
probes to Europa and other solar-system bodies rich in potential vent
fields, a comparative biology to life on Earth may yet be found within our
lifetimes.
Adrian Glover is a researcher at the Natural History Museum, London, in
the Polychaete Research Group.
