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Biosphere as Place

Ocean: Benthic Biomes 2

 

 
Deepest Creatures
 
Chemosynthetic Oases in the Deeps
 
Hydrothermal Hot Vents
 
Lost City Warm Vents
 
Cold Seeps and
Chemosynthetic Biological Communitie
s
 
Whale Falls

 

 

Deepest Creatures

Animals that make the abyssal depths their home have adapted to extreme constraints on life.

• Water temperature just above freezing
• low oxygen in water
• the weight of miles of water pressing down
• very saline water

The frigid water and the low oxygen content both result from poor circulation of abyssal water. This water five to ten miles below the sunwarmed surface waters may not see the sun for hundreds of years and must come in contact with air if it is to increase oxygen content. The more salty water is, the heavier it becomes, so it sinks. The seafloor hosts the saltiest waters in the ocean.

The ecology of the abyssal benthos features very slow rates of decay, slow metabolism in all animals, which translates into slow growth, slow reproduction, and very long life.

Many kinds of animals have succeeded in adapting to these conditions. Some are bottom-feeding, or demersal fish. Many live on the seafloor surface, and either eat each other or live on the very slim pickings that slowly fall down from the surface--dead plankton, dead algae, mostly microscopic. Many meiofauna do well by eating protozoans, which in turn eat bacteria. Most abyssal animals are hungry.

Consider what you might look like adapted to the abyss. A pancake? A thick coat of paint?

Here are a few of the adapted Creatures of the Abyss:

A benthic squid flaps away from a submersible, dangling fifteen foot tentacles
photo courtesy MBARI
Giant isopod is over a foot long. Compare to terrestrial pill bug
The skirted Grimpoteuthis is like both octopus and squid, with features of each
A batfish on the abyssal sediments of the Gulf of Mexico
The shield octopus Grimpoteuthis of the deeps. It is nicknamed Dumbo beause it flies through water with its two earlike fins. photo courtesy BBC Blue Planet
The flytrap anemone has a unique method of engulfing prey.
photo courtesy NOAA
One of most elaborate sea cucumbers in the abyss.
Abyssal amphipod photo credit National Geographic
Abyssal comb-jelly photo credit National Geographic
Abyssal glass squid photo credit National Geographic
sea squirt of the deep seabed of the Tasman Fracture off Australia
orange bamboo coral about five feet tall off Hawaii at a depth of 5, 745'
Image courtesyHawaii Deep-Sea Coral Expedition 2007/ NOAA
abyssal squid Magnapinnis
off West Africa, Atlantic
photo courtesy Smithsonian

abyssal squid Magnapinnis
Indian Ocean photo courtesy IFremeri
tiny illuminated telescope octopus
photo credit Steven Haddock
glowing sucker octopus uses lights in its suckers to attract its main prey, copepods
photo credit Claire Nouvian
vampire squid in full color; entire skin covered in photophores (light cells) ready to signal or hide.
vampire squid in stealth mode; red in pitch black is invisible
An abyssal sea cucumber
with nothing to hide
Another view of the shield octopus Grimpoteuthis of the deeps.
A stilt-finned fish stalks across
abyssal sediments.
one of many kinds of abyssal polychaete worms that tunnel the sediments

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Chemosynthetic Oases in the Deeps

Since the late 1970s, scientists have begun to explore the deeps with cameras and scoops on remotely operated submersible vehicles (ROVs). Their discoveries have completely changed our vision of the abyss. Previously it was generally assumed that the deep seas were virtually barren of life and barren of any interest.

To general surprise, scientists have discovered many communities of unknown animals in the deeps, a thinly spread macrofauna benthos, a numerous meiofauna (tiny but visible animals) benthos, and a large protist community of forams and radiolarians.

But it is the discovery of deep sea hotspots crowded with life that has captured the public imagination:

     
 
Lost City hydrothermal warm vents--methane and hydrogen chemosynthesis
Cold Seeps:Chemosynthetic Biologic Communities
 
Whale Falls: the century-long communities
of whale death

Most importantly , we discovered that photosynthesis is not the only method life has to create chemical energy, otherwise known as food.

The other methods were invented by ancient bacteria, which have invented every great life strategy.

Rather than using sunlight in photosynthesis, these bacteria living in total darkness use sulfur compounds (hydrogen sulfide) dissolved in the hot water from hot vents. They are chemoautotrophs, self-feeders using chemicals instead of light.

Some of these wily microbes use methane instead of sulfides. In this purely chemical process, they create sugars and proteins as end products just as in photosynthesis.

As these early deep ocean explorations continue, we find again and again that Earth is active in ways we had not imagined.

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Hydrothermal Vents

Seafloor is thinner than the continental plates, but more dense and brittle; seafloor crust ruptures at junctions of tectonic plates around the globe. Sometimes these ruptures are dramatic, as at the Mid-Atlantic Rift, plates are slowly moving apart and red-hot magma oozes up to make new seafloor. Hot vents often appear in rocks of ocean ridges.

Here are some 'faces' of the hydrothermal vent community:

hydrothermal vent, or black smoker, near the mid-Atlantic Ridge. Chimneys are made of minerals precipitated from the hot water jetting out.
A multitude of tubeworms and mussels are swarmed by shrimps
Giant chemosynthetic vent clams cluster the fissure in basalt that leaks sulfides.
close view of ventimiferan tubeworms
fish cruises among hot vent chimneys
new kind of squat lobster with "furry" setae, or bristles, that are thickly colonized by bacteria, a relationship not yet understood. Photo credit MBARI
Riftia tubeworms, some with attached mussels. Both animals live through symbiosis with sulfide-digesting bacteria inside their body tissues.
A host of tubeworms with gills extended are supported by
the sulfides pouring from chimneys
.

Stauromedusae, a stalked jelly relative, living at the Medusa vent off Costa Rica, at over a mile deep.These have been found at several Pacific vents, but their larvae do not swim. Photo © MBARI

An eel-like fish hunts among giant tubeworms at a hot Pacific vent
image by Stephen Low Co. & Rutgers University

Stunnning chimneys at an Atlantic mid-ocean ridge site
image by Stephen Low Co. & Rutgers University
White crabs line the edges of a rift near a hot vent. Geology here is unstable.
Crabs and shrimps graze rocks and the shells of chemosynthetic mussels.
A chemosynthetic tubeworm with
very different stalks
octocorals colonize the top
of a dead vent chimney
a skate ventures to the busy depths of a hot vent community.
An improbable pyramid of vent mussels attached to one another.
translucent stauromedusae near East Pacific vents, photo © MBARI
Stauromedusae attached to basalt near vent on East Pacific Rise, photo © MBARI
New Family of deep-sea crab from hot vents. Its conspicuous fur has given it the informal name, Yeti crab, after the hairy abominable snowman. The setae, or bristles, are full of chemosynthetic bacteria, which may possibly be a source of food for the crab, or may detoxify sulfur compounds from the vent. The crab actively holds its furry pincers over flowing vents, which strongly suggests symbiosis.
Photo courtesy of Michel Segonzac, IFREMER)
Translucent stauromedusae jellies festoon a dead vent chimney in every position, showing the chalice body, the stalked attachment, the eight clusters of eight tentacles.
photo courtesy of Janet Voight and the Field Museum

More than 500 new animal species have been found at hot vents since such vents were first discovered in 1977 off the Galapogos Islands. Picture the cold ocean bed, water slightly above freezing, and a hot spring suddenly spews hot water at 500 degrees C. out of the seafloor. The water is heated by magma just below, often where new seafloor is being formed. These vents are loaded with dissolved minerals, which over time deposit "chimneys" extending up many feet. Some of these minerals are sulfides, which attract bacteria that know the trick of converting sulfur compounds into food (chemosynthesis). In a few months, very fast for the deeps, a whole community of life comes into being, a kind of hotspot of life. Some recently discovred vent animals were previously unknown, such as the giant tubeworms that receive nutrients directly from bacteria inside them; the worms have no digestive system. Large mussels and clams have also adapted to symbiosis with these chemautotroph bacteria that make food without photosynthesis. A host of white crabs, pink shrimps, white sea stars, sea cucumbers, and occasional bottom-feeding fish round out the vent macrofauna.

The search for new vent fields has become intense. A recent Chinese expedition has found a vent field in the Indian Ocean; European and American scientists have recently found vent fields in the Arctic, in an Iceland fjord, and off the Pacific coast of Costa Rica. A series of expeditions in 1998-19999) with the submersible Alvin found many new vents on the Southern East Pacific Rise, the ocean ridge mountain chain of the Pacific. (Link)

Map of some hydrothermal vent locations image courtesy of Nature

Hot vents have limited lifespans. The first vents ever discovered (in the Galapagos) are now dead and cold--a vast array of gaping clamshells and slumped tubeworms. In the Galapagos, the tectonic plate is moving faster than the magma beneath. How fragile life is and how suddenly life can end.

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Lost City, A New Kind
of Hydrothermal Vent

A new and different kind of hydrothermal vent has been recently described. It is not a “black smoker” whose heat (up to 700 F.) is from magma seeping through the seafloor crust. Instead, this new kind of vent is heated entirely by a chemical reaction between seawater and peridotite rock. The water streaming from the new vents is only hot enough to shimmer (up to 170 F).

The new vent field perches on top of a twelve mile (20 K). long seamount, the Atlantis Massif, near the Atlantic Ridge. Lost City is 2,600 feet (800 m.) below the surface.

Carbonate minerals paint nearby outcrops brilliant white, and form vents ranging in shape from tiny toadstools to a 200 foot column named Poseidon.

A thirty foot carbonate tower at Lost City
photo credit University of Washington
Click to enlarge

Freshly-deposited carbonate
on this ancient tower is bright white.

photo credit University of Washington.
Click to enlarge

Peak of 'beehive'
on a carbonate tower.
Photo credit U. of Washington. click to enlarge
One pinnacle of 60 meter (200 foot) Poseidon tower. New carbonate deposits here are fragile and porous. Photo credit U. of Washington. Click to enlarge

Microbe Biofilms from chimney interior. In filament strand on right, each dot (microbe) in strand is one micron. Microphoto credit University of Washington. Click to enlarge

Huge flange on tower side deposits new carbonate as water flows.
Photo credit U. of Washington. Click to enlarge
deepwater cup coral Desmophyllium at Lost City. image credit Tim Shank, Woods Hole Click to enlarge
Living biofilm on carbonate
photo credit Matt Shrenk, U. of Washington
"antler" formation
photo credit NOAA Click to enlarge

two carbonate towers in rov lights
photo credit NOAA Click to enlarge
spectacular tower, rov lights
photo credit NOAA Click to enlarge
submersible Hercules lights IMAX tower photo credit U. of Washington click to enlarge
A wreckfish patrols the Lost City carbonate spire.
Photo credit U. of Washington. click to enlarge

Lost City was discovered by chance in 2000, during an Alvin dive to the Atlantic Mid-ocean Ridge, and is still being explored. Only some local sediments  have been sampled. Many of those sediments were deposited during the last glacial maximum 20,000 years ago, according to Swiss scientists.

Biomass at Lost City is primarily microbes, archaea and bacteria. Their numbers are immense. An estimated one billion cells inhabit each gram of the porous rock of Lost City. Some of these feed on hydrogen and produce methane. Others feed on methane. Both kinds produce carbon compounds as by-products; scientists speculate that some of these complex molecules may have given rise to life.

Differences between the warm Lost City vents and  very hot “smoker” vents are striking.

Lost City warm vents
Black Smoker Hot vents
Lost City carbon-dated at 30,000 years. Peridotie rock reacts chemically with alkaline seawater to become serpentine rock--no magma connection. Smokers are short-lived, depend on volcanic activity. Hot spots in the magma shift locations as the seafloor plate moves. The first smoker system discovered in the 1970s is now lifeless.
microbes live in very
alkaline water
microbes live in very acid water
chemosynthetic microbes feed on methane, hydrogen compounds chemosynthetic microbes feed on sulphur, hydrogen compounds
diverse meiofauna, tiny and transparent, hard to see diverse meiofauna, overshadowed by large animals, hard to see
small but diverse macrofauna; deep corals, fish, crustaceans
huge diverse macrofauna; tubeworms, mussels, shrimps and crabs.
microbes live on and inside chimneys in biofilms microbes live in tubeworms, mussels, clams and in chimneys
Lost City chimneys are white to gray carbonates and tall, up to 200 feet (60 m.), and thousands of years old.. Smoker Chimneys are dark and made of metal-rich mineral compounds, much shorter ,30 feet, comparatively brief lifespans.

Scientists are impressed with how stable and long-lived the Lost City vent field is, and wonder if this sort of vent-field running for thousands of years might improve the chances for life to spark and to be sustained until it could take hold.

"It's difficult to know if life might have started as a result of one or both kinds of venting," says Deborah Kelley, University of Washington oceanographer, "but chances are good that these systems were involved in sustaining life on and within the seafloor very early in Earth's history."

Researchers are intrigued by Lost City partly because it may give us insight into the conditions that might foster life on other planets.

Note: Several of the above photos were first published in Oceanography, Vol 18, No.3, Sept. 2005 to illustrate Mantle to Microbes, by Deborah S. Kelley.
Download .pdf file
1.67 MB

 

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Cold Seeps

Cold seeps are places on the deep ocean floor where hydrogen sulfide and methane seep or flow from bottom sediments. They support chemosynthetic communities based on bacterial food production much like the hot vent communities. But cold seeps are often small in area, and the numbers of organisms comparatively small. They are called "cold" in contrast to hydrothermal vents, which spew super-heated water.

Cold seeps were first discovered and named by the Monterey Bay Aquarium Research Institute. But those same researchers now find that many chemosynthetic biological communities (CBCs) exist without any seepage at all. MBARI's key finding is that CBCs develop where previously buried sediments have been exposed, by erosion or slides. Animals in seep communities such as tubeworms grow "roots" that penetrate sediments and rock fissures in a way analogous to plant roots. CBCs are small communities, but much more common than their larger hot vent relatives. Since many CBCs do not depend on active seeping, they may have longer lifespans than hot vents.

CBCs are based in chemosynthesis, with tubeworms, mussels and clams the root inhabitants, but often include anemones and other invertebrates that do not depend on sulfide- or methane-feeding bacteria.

In CBCs, tubeworms grow very slowly and live long, like most abyssal animals. In contrast, hot vent tubeworms grow rapidly and die young.


Here are some 'faces' of Cold Seeps , aka CBCs:

chemosynthetic clams
characterize cold seeps
CBC hotspot: tubeworms, mussels, crabs and eels make a tangle of life.
tubeworms thrive next to methane hydrates deep in the Gulf of Mexico
photo credit Ian MacDonald
mussels, tubeworms, crab
at a cold seep
this abyssal hermit crab hosts bacterial "fur" on its pincers

 

a unique species of polychaete worm lives in burrows in methane "ice" (methane hydrate) outcrop in the abyss of the Gulf of Mexico. Photo credit Ian MacDonald
crabs foraging among thriving chemosynthetic mussels and tubeworms


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Whale Falls

Whale falls are simply the carcasses of dead whales that have fallen to the seafloor, often into abyssal waters, where cold and pressure slow down decay. A dead whale weighs somewhere between 60,000 and 320,000 pounds, which is an enormous influx of organic matter into a relatively food-challenged ecosystem.

In 1987, the submersible Alvin spotted a blue whale skeleton on the seafloor that was seventy feet of bones carpeted with life from worms to bacteria.

A whalefall bonanza quickly becomes a banquet for scavengers such as hagfish, sleeper sharks, eels, squat lobsters and other crustaceans. These feed for generations on the whale's soft tissues. Meanwhile, a substantial life community grows up in the sediments near the carcass; they are enriched by its decay. After that, there are the whale's huge bones, which, unlike the bones of most skeletons, are rich in fats and oils. Whale bones are rich in sulfur compounds, which attract sulfur-digesting bacteria and their symbiotic partners, such as Osedax worms which "burrow" into the bones with rootlike structures and wave their red gill plumes into the water for oxygen. By this late stage of decomposition, even sea anemones can make a good living at the whale fall. The community becomes complex and can persist for a century or so. Some 190 species of animals have been found on a single whale skeleton. Life is slow-paced in the cold depths of the sea, and so is decay. Meanwhile, generations of mussels, clams and osedax worms thrive on and near the bones.

Craig Smith of the University of Hawaii is the leading researcher of whale falls. He has arranged to be notified when a dead whale is washed up on a Hawaii beach; he then assembles a crew to tow the whale out to sea and sink it. This is difficult, since decay gases make the whale bouyant, so they weight it with large quantities of scrap iron until it sinks. A buoy is attached so they can return periodically for research.

Some 'faces' of the whale fall community:

montage of a whale fall rich with life: sea cucumbers, crabs and
myriad Osedax worms waving red gill plumes. Photo courtesy MBARI
many eels wind through the ribs and vertebrae of a fallen whale.
Photo courtesy NOAA

Photo courtesy Greg Rouse
An Osedax worm removed from the bone. Gills on top reach out of the bone, The green 'roots' are at the bottom, and the white ovaries are at the center. The submersible's arm retrieves an old fragment of whale bone that supports a thriving host of Osedax worms
The fauna on and around the whale skull include an octopus, two kinds of crabs, and sea anemones, plus an assortment of meiofauna we can't see, plus the biiions of procaryotes that are the source of this self-sustaining food web.
crabs cluster on the separated vertebrae of a long-fallen whale
Photo courtesy JAMSTEC

 

Explore Further in Biosphere

 
Biosphere: Introduction
 
Biosphere as Place: Introduction
 
Biosphere as Ocean: Life Zones
 
Biosphere as Ocean Floor: Benthic Biomes One
 
Biosphere as Ocean Floor: Benthic Biomes Two
 
Biosphere on Land: Terrestrial Biomes
 
Biosphere on Land: Anthropogenic Biomes
 
Biosphere as Process: Introduction
 
Biosphere Process: Floating Continents, Tectonic Plates
 
Biosphere Process: Photosynthesis
 
Biosphere Process: Life Helps Make Earth's Crust
 
Biosphere Process:
Rock Cycle--Marriage of Water and Rock
 
Biosphere Process: Marriage of Wind and Water
   
Biosphere Process: Gas Exchange
 
Biosphere as An Expression of Spirit
 
The Ecological Function of Art
 
The Earth Goddess
 
The Tree of Life
 
The Green Man
 
Earth Art
 
Biosphere as Community
 
Biosphere Microcosm: Bacteria and Archaea
The Procaryote Domain
 
Biosphere Microcosm: Germs
 
Biosphere Community: The Eucaryote Domain
 
Biosphere Community: Protists 1: Algae
 
  Biosphere Community: Protists 2: Protozoa
 
Biosphere Community: Plants: What's New?
 
Biosphere Community: Plant Diversity--Major Groups
 
Biosphere Community: Plant Defense
 
Biosphere Community: Plant Pollination
   
Biosphere Community: Plant Seed Dispersal
 
Biosphere Community: Kingdom Animals
 
Biosphere Community: Kingdom Fungi
 
Biosphere Community: Six Great Extinctions
 
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