Journey into the deep

Their vessel was the bathysphere, a primitive spherical tethered submersible. Here, Trinidadian biologist Dr Diva Amon recounts her experience of heading even deeper than Beebe, journeying to 2,382 metres below the ocean surface in the Cayman Trench:

June 25, 2013, Cayman Trench, Caribbean Sea: Today is the day that, as a deep-sea biologist, I have dreamt about for many years. I will imminently be undertaking my first journey down into the dark, unexplored depths of the deep ocean. My mode of transport will be the Shinkai6500, a manned submersible operated by the Japan Agency for Marine-Earth Science and Technology (Jamstec), capable of diving to depths of 6,500 metres, although my goal is just over a third of that.

My mission is to find the Von Damm hydrothermal vent field and collect samples for colleagues.

This month-long research expedition is part of an around-the-world voyage of discovery by the Shinkai 6500 and its support ship, the RV Yokosuka, called the Quest for the Limit of Life (Quelle).

9.30: I am crammed into the two-metre-diameter spherical pilot chamber of the Shinkai6500 with the two submersible pilots, Yoshitaka Sasaki and Akihisa Ishikawa.

The titanium-alloy sphere we are sitting in is seven centimetres thick; this is necessary to withstand the extreme pressures we will experience during our dive. I watch with my knees hunched up to my chest as Sasaki-san inspects the hatch for foreign objects before closing it. Even something as small as a single strand of hair could have disastrous consequences at depth.

9.45: I move into the foetal position so I can look out of the viewing port to wave goodbye to friends, colleagues and daylight.

There are three viewing ports in the sphere, one for each passenger. I look at the 14-centimetre thick porthole hesitantly, silently reminding myself that this will be the 1353rd dive of the Shinkai6500. I’m not afraid but I’m definitely nervous and extremely excited to head down into this unknown realm.

10: The submersible is hoisted up on a huge A-frame and moved to the stern of the RV Yokosuka.

From there, we are lowered into the Caribbean Sea where we remain attached to the ship by a series of ropes. From the porthole, I catch glimpses of the two divers charged with the task of detaching the submersible so we are free to make our descent uninhibited by any physical connections to the ship. I am grateful to be doing this dive on a calm day as the submersible moves around enough as it is.

I can imagine that if it were any rougher, it would be like being in a washing machine. I’m beginning to boil as the Shinkai6500 has no temperature-regulating system and I’ve been advised to wear thermal underwear and an insulating jumpsuit. The sphere tends to mimic the temperature of the surrounding medium and right now that’s the 28°C surface water of the Caribbean Sea.

10.21: 0 metres –After what seems like a nauseating hot lifetime, we begin descent. I press my face onto the porthole staring into the deep-blue ocean not wanting to miss anything exciting. We have each been given a bento box, chopsticks and a flask of green tea for sustenance during the eighthour dive. I pack mine away safely for later. My lips are parched as I haven’t drunk anything since the previous night’s dinner and yet I don’t anticipate drinking anything more during my time in the Shinkai6500. I have made a purposeful decision to dehydrate my body to prevent myself from needing to use the bathroom during these eight hours. The sphere is two metres wide; there is not enough space to stretch out my legs, much less for a toilet. During my briefing yesterday, I was advised that my options for dealing with this issue were either to a) wear an adult diaper (mortifying); b) use a female urination device (which would involve having to remove my insulating overalls and thermal underwear while having so little space or privacy that I am literally touching the two male pilots); or c) dehydrate myself. It was an easy decision.

10.30: 300 metres –My eyes are no longer able to pick up any sunlight. The surrounding sea has changed from deep blue to ink black. The air in the submersible is cooling down as quickly as we are descending.

10.50: 1,000 metres –We enter the midnight zone. I cup my hands around my face and onto the viewing port to try to block out the few lights from the instruments inside the submersible. My eyes acclimatise allowing me to see a constant stream of light streaks and fireworks whizzing vertically by. These are the bioluminescent displays of deep-sea animals and they vary from rhythmic flashes to squirts of light triggered by the passing of our submersible. I have never been privy to this spectacle as all the previous deep-sea expeditions I have taken part in have used Remotely-Operated Vehicles (ROVs) with cameras that are not as sensitive as the human eye. My leg is beginning to go numb but I can’t bear to tear myself away from the window to change position.

11.27: 2,362 metres –The deepsea floor is in sight but we are still 20 metres off. I can’t help but smile and think “Wow! I’m really down here!” I suddenly realise I’m cold and my shoulder is wet. I zip up my overalls as Ishikawa-san explains to me that as the air inside the submersible cools, the water vapour condenses and trickles down the sides of the spherical chamber.

11.29: 2,382 metres –Touchdown! I have only a few spare minutes to admire the view while the pilots adjust the buoyancy of the submersible. As there is no light this deep in the ocean, we can only see as far as the lights of the submersible shine, which is about 30 metres here. The offwhite sedimented bottom appears a beautiful blue.

Apart from violet sea cucumbers dotting the seafloor, I don’t see much other life. This is what most of the world’s deep sea floor looks like: lunar, barren and eerie.

The deep sea is not an easy place to live: it is completely dark, extremely cold (about 4°C), has very high pressures (237 times the atmospheric pressure we feel at sea level on a day-to-day basis or about what your big toe would feel like if there was an SU V on it) and there isn’t a lot of food to eat. The hydrothermal vents we aim to visit, however, are very different.

Hydrothermal vents are submarine springs that spew out hot, mineral-rich water and are known to occur along all midocean spreading ridges, back-arc spreading centres and at some seamounts.

Seawater percolates into the seafloor through fractures, much like rain percolating into soil. This seawater is then heated by the high temperatures within the crust, allowing minerals from the surrounding rocks to dissolve into the seawater altering its chemical composition.

The seawater then rises due to convective heating and is expelled out of the crust as hydrothermal fluid. When the hot hydrothermal fluid meets the much colder seawater of the deep sea, it cools rapidly.

This rapid drop in temperature means that many of the mineral ions accumulated in the crust, are precipitated out as metallic compounds which form a billowing plume of smoke-like particles that can be black or white. Some of these metallic particles deposit around the vent opening, in time building up to form the chimney- like structure.

Chemicals, such as sulphides, found in the hydrothermal fluids are used by bacteria living around the hydrothermal vents, to generate energy in a similar way to plants using sunlight on land (chemosynthesis in the deep sea vs photosynthesis on land). These bacteria are the bottom of the food chain at these vent habitats, providing food to enormous communities of weird but wonderful animals.

These unique habitats are like rich oases of life on the otherwise desert-like, deep-ocean floor.

Hydrothermal vents were first discovered in the late 1970s on the Galapagos Spreading Centre and since then there have been over 250 active hydrothermal sites confirmed with many others inferred worldwide. Their discovery changed our understanding of life on our planet and is reported to be one of most important finds of the 20th century. Since their unearthing, deep-sea hydrothermal vents have provided insights into geological processes associated with seafloor spreading, the geochemical balance of the oceans and the cooling of the Earth.

11.31: 2,382 metres –It’s science time! As only one scientist can fit in the Shinkai6500, I have been bestowed with a “to do’ list compiled the night before by all the scientists on board the ship. It is 31 items long and ranges from locating and collecting experiments to sampling hydrothermal-vent fluids, rocks and animals. The samples collected will aid in our understanding of the habitable limits of life in extreme deep-sea environments. With less than five hours of bottom time, every minute is precious.

Be sure to join us for part two of Dr Amon’s amazing journey and see what the team discover on the sea floor in next week’s Trinidad and Tobago Field Naturalists’ Club feature. For more information on our natural environment, contact the TTFNC at admin@ttfnc.org or visit our website at www.ttfnc.

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