The deep sea is the last frontier on Earth. It remains the least explored habitat available to the plethora of multicellular organisms inhabiting our planet. Given that the over 70% of the Earth's surface is covered by the oceans and that over 90% of the total volume of the oceans is in waters deeper than 200 m depth, this means we can safely say that "we know less about the largest habitat on Earth than about any other habitat."

the Milky Way!

an unmanned probe deployed

into the sea

天の川無人探査機着水す

ama-no gawa mujintansaki chakusui su

a shooting star…

the ocean floor to far below

to drop anchor

流星や錨届かぬ海の底

ryuusei-ya ikari todokanu umi-no soko

The deep sea presents a unique set of challenges that have led to the present state of affairs where more is known and better maps exist for our galaxy than for the ocean floor. The national budget for marine research in the U.S. is only around a quarter of that for space research and in Japan is less than one fifth, but this is not the only reason our oceans remain largely unexplored. An expedition outside of our Earth's atmosphere must cope with the vacuum of outer space but this is only a pressure difference of one atmosphere. In contrast, the average depth of the oceans is around 4000 m, translating into a pressure difference of around 400 atmospheres, while at the bottom of the Challenger Deep in the Marianas Trench - the deepest place on Earth - that pressure difference would be more then 1080 atmospheres! Special tools are needed to study the diversity of organisms living at these depths.

the Shinaki submersible -

swallowed up and on its way

to the Underworld

「しんかい」や涅槃の浪に呑まれけり

shinkai-ya nehan-no nami-ni nomare keri

Manned submersibles and unmanned probes such as ROVs (remotely-operated vehicles) and AUVs (Autonomous Underwater Vehicles) allow humans to either see directly and/or record images of the denizens of the deep. Many of these organsims seem to have been spawned in Hell with long fangs, glowing bodies, strange eyes and hugely extendable stomachs being some of the adaptations seen in deep sea fishes. Other animals live around volcanic vents that spew hot water and gases into the surrounding waters - blind crabs and shrimps, huge tubeworms with bright red gills and gigantic clams being some examples. These animals thrive on poisonous gases such as hydrogen sulphide or methane emitted from the vents and taken up by bacteria living symbiotically within their bodies and that can convert these gases into food for their hosts. The majority of deep sea animals, however, are predators floating silently in the dark waiting for their next meal or detritivores that feed on the organic matter called marine snow that falls from the sunlit surface layers into the ocean's depths.

through Picasso's blue

and on the other side a crimson

sea slug swims

ピカソの青過ぎて深紅のユメナマコ

pikaso-no ao sugite shinku-no yumenamako

Perhaps the most successful of these floating predators are not the charismatic bony fishes but are rather the diaphanous jellyfishes. On my first dive in a manned submersible I was astounded to see the diversity of jellyfishes that passed before the porthole. Their watery bodies need much less energy than scales and muscles to produce and maintain, and with the lack of waves or turbulent currents they are seldom returned to their element by a fluke of nature.

all dried out

the height of these jellyfish...

A-Bomb Day

乾ききし水母の嵩や広島忌

kawaki kishi kurage-no kasa-ya hiroshimaki

A little organic matter can stretch a long way when your body is over 95% water and the longest animal on our planet is not a blue whale but rather is a colonial jellyfish called a siphonophore with a length of over 40 metres! Such a colony can have hundreds of stomachs, each dangling down a tentacle to form a veritable curtain of death for any krill or fish that is heading to the surface to feed under the cover of the darkness of night. As these sated animals return to the depths before dawn the siphonophores once again feast on the unlucky migrants. Jellyfish also have an amazing capacity to regenerate if they are damaged and some of these huge colonies may be hundreds of years old.

picking up a jellyfish...

my lifeline

clear and deep

掬う掌のくらげや生命線ふかく

sukuu te-no kurage-ya seimeisen fukaku

Silk or nylon nets are often used to collect the floating inhabitants of the open ocean - the plankton. A single haul of a plankton net to 1000 m off the coast of Japan can yield over 50 species of jellyfishes. The same net can contain over 250 species of small crustaceans such as copepods, amphipods, ostracods and krill, in addition to species from other groups such as arrow worms (>25 species), polychaete worms, nemertean worms, pelagic tunicates such as salps, doliolids, larvaceans and pyrosomes, fishes, shrimps and squids. How all of this biodiversity can co-exist in an environment that is devoid of shelter such as plants, rocks, mud or sand is an as-yet-unsolved question termed "the paradox of the plankton". It is hoped that an explanation of this paradox would also enable us to understand better the mechansims by which diversity is produced and maintained in other ecosystems such as rainforests, savannahs, deserts or tundra by unveiling paradigms that have as yet eluded us.  

Many of the animals that inhabit the deep ocean are too fragile to collect in nets, being strained through the mesh like so much gelatinous spaghetti. The comb jellyfishes or ctenophores are one such group. Although referred to as jellyfish these ctenophores lack the venomous harpoons called cnidae that the true jellyfishes, or cnidarians, use to capture their prey. They instead have "sticky cells" called colloblasts that glue their prey to them like flypaper and swim by beating the 8 rows of cilia that line their bodies like the oars from the longboats of yesteryear. Their bodies can be up to 98% water and even if one is fortunate enough to capture one for study they rapidly disintegrate upon death and most species are unable to be preserved in their original state in chemical fixatives such as alcohol or formalin.

shadows, jellyfish,

clouds, and Me as well

pass by -- this beach

影・クラゲ・雲・この俺も去り行く濱

kage, kurage, kumo, kono ore-mo sari yuku hama

looking up

the shadow of a jellyfish

the wake of my child

見上げれば水母の影と吾子の水脈

miagereba kurage-no kage-to ako-no mio

Such animals are best studied using submersibles and robot probes, which also allow their behaviour in the field to be observed. Not only can they be observed eating crustaceans such as krill or feeding on other jellyfishes but often they are adorned with smaller creatures living on their outer surfaces or burrowed deep within them. Just as the trees in a tropical rainforest provide a suitable habitat for various insects, so to it seems with the jellyfishes of the deep sea. Some insects live and feed on the leaves of a certain tree while another insect species might live beneath the bark or in the roots. I have seen a jellyfish with one species of crustacean attached to the outside of its umbrella while another species lived nestled next to its mouth. Marine snow can also provide a habitat separate from the surrounding water for some species to use. The ability to observe such associations with modern survey techniques has brought us one step closer to solving the paradox of the plankton. The development and application of in situ holography, robots that can track animals autonomously over 24-48 hour periods, electronic tagging of small animals and/or their predators with data loggers, and a host of other new technologies may one day allow us to study the oceans in a transparent manner, to bring our knowledge of this ecosystem - the largest on the planet - to the same level as our knowledge of terrestrial ecosystems and help us to manage it effectively before it too is altered beyond reprieve.

out on the sea

coming back we meet again -

my shadow!

海へ出て戻れば影に再会す

umi-e dete modoreba kage-ni saikai su

 

*PHOTO
1.Micrograph of Deep-sea Creatures taken by the Visual Plankton Recorder
2.Apolemia-fuzzy
3.rhb-BW-2-2-Eurhamphaea-vexilligera-DSC_0172

 

　Profile of Dhugal Lindsay

 

Dhugal John Lindsay (b. 1971) is a Research Scientist with the Japan Agency for Marine-Earth Science & Technology (JAMSTEC) and holds adjunct professorships at Yokohama Municipal University and Kitasato University. Dr. Lindsay's research focuses on mid-water ecology, particularly concentrating on gelatinous organisms. Dr. Lindsay has extensive experience with the Japanese research vessel and submersible fleet, both as Chief Scientist and as a member of multidisciplinary teams.

He is Project Leader of JAMSTEC’s PICASSO Project.  He served on the Steering Committee of the Census of Marine Zooplankton (Census of Marine Life: CoML) and on the National Regional Implementation Committee for Japan.

Dr. Lindsay is also a renowned and prolific haiku poet, working in the Japanese language and is the recipient of the “7^th Annual Nakaniida Grand Haiku Prize” for the best debut work by a haiku poet working in the Japanese language for “The mudskipper” (Mutsugoro).  His work has also been published in the books Haiku Seasons (in English), Global Haiku (in English), Haiku sans frontiers (in English and French) and so on.