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Offshore
New Providence, Bahamas, Day 1,1999

With this dispatch
from sea, we begin an extraordinary expedition to the Bahamian archipelago,
to search for slitsnails, wonderfully strange and primitive deep-sea
gastropods living at crushing depths in inky black waters. Dr. Jerry
Harasewych (right) from the Smithsonian Institution is leading the team
to the seafloor in his effort to understand the natural history of the
second largest living group of animals on Earth, the mollusks.
By midnight
Saturday, every member of the crew was on board the Research Vessel
Edwin Link, and four hours later the ship left the dock at Nassau for
open water. Out at sea, 10-12 foot waves breaking over the bow forced
us to sheltered water--vestiges of hurricane Irene. The ship's crew
and the research team held their first dive meeting Sunday morning at
7:30 am, and the sub was launched at 8:00 am with two scientists and
two crew.

One can tell from
the energy and excitement that launching the submersible is the real
beginning of the expedition. Diving through pitch black, the sub held
at a depth of 2,500 feet off the northwest corner of New Providence.
With lights and cameras turned on, the pilot slowly cruises the steep
slopes while the team searches for samples. The landscape looks lunar;
steep slopes are layered with fine chalky-looking sediments. Mostly,
there is a look of desolation, a starkly beautiful underseascape that
comes wonderfully alive when the powerful lights of the sub shine over
it. In fact, the few individual corals and sponges that we see are dusted
with sediment. A light and continuous rain of organic sediment filters
down. It is "snowing" shells of planktonic organisms from near the surface.
Without light and photosynthetic organisms, the possibility of life
at this depth seems improbable.
But we see a number of animals, never abundant, yet there. Tiny fishes,
odd and wonderful--like little birds, occasional squid and octopuses,
sea stars, brittle stars, sea cucumbers (that swim away when disturbed),
a giant isopod, and then the deepest dwelling slitsnail known, the King
Midas slitsnail (Perotrochus midas). Midas stands out among the
beige sediment, its shell a reflection of iridescent pearl and gold.
The animal has a large ivory-colored foot and head, and strangely, two
small eyes, or light receptor organs.
The search for slitsnails
is by no means random. Jerry knows that Midas occurs only within a narrow
temperature range, between 8.0--10.0 degrees centigrade. There is a
thermal gradient running from the warm surface waters to the cold, deep
waters
surrounding the Bahamas. The search for Midas is carefully planned.
Using depth charts and knowledge of deep sea temperatures in the region,
and locating steep slopes, all increase the likelihood of finding this
beautiful animal. In fact, Midas is found on such steep slopes that
if one is knocked loose by the mechanical arm, it may tumble 50 feet
or more and is hardly ever recovered.
On our first day
Jerry dove twice accompanied by José. Five specimens of Midas were collected
on the first dive, three on the second, a success for the team, or as
Jerry says, "it's like walking a straight line across a tiny fraction
of Africa looking for elephants. What are the chances that one will
cross your path?" Actually, what this team is doing is much harder than
that. The lights on the sub only illuminate a small area of the landscape,
so peering out at the seafloor is like looking through a keyhole. Adding
even more difficulty to the situation is the optical effect of the sub's
Plexiglas bubble. Looking through the bubble, everything appears much
smaller than actual size, so a four inch diameter shell looks to be
about the size of a dime.
The team will be
diving for Midas over two days, four dives altogether, and then the
ship will head off to Chub Cay in search of another gastropod, Andanson's
slitsnail (Entemnotrochus adansonianus). Future reports will
explain more about the sub and other equipment, and the kinds of research
the team is carrying out.
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