Life Near Deep Sea Vents
During 1977, three scientists dived into the Pacific
Ocean in the small submarine named Alvin. They dove so
deep that sunlight did not reach them. Around 8,000 feet
below the surface, they were surprised to find a huge
change in temperature. Within a short distance, the
temperature of water changed from near freezing to about
400°C. The extremely high pressure of ocean water
prevented the hot water from boiling. The scientists also
Diving along the mid-ocean ridge, scientists within
the deep submersible, Alvin, peered through their
discovered vents on the bottom of the ocean. Hot fluid
tiny portholes to see an astonishing sight: Clouds of
poured out of these hydrothermal vents.
billowing black “smoke” rising rapidly from the tops
tall rocky “chimneys”. The “smoke” consisted of
Further deep sea studies revealed that vents occur in ofdark,
fine-grained particles suspended in plumes of
hot fluid, and the “chimneys” were made of minerals
areas where the Earth’s tectonic plates are slowly pulling
that were rich in metals.
apart. In these areas, molten rock rises from the earth and
cracks the ocean floor. As seawater flows into the cracked sea bottom, the water contacts
molten rock and becomes superheated. The hot, acidic water dissolves minerals while it
concentrates sulfur and other chemicals. When the hot water mixes with the frigid deep sea
water, the dissolved minerals become solid and form chimneys. One type of chimney is
made of a chemical called iron sulfide. Because iron sulfide is black, these vents are called
black smokers. The chimneys can reach 180 feet high and contain fluid that is hot enough to
melt solid metal.
The Alvin crew also discovered a colony of strange animals living around the deep
sea vents. The scientists were shocked to find animals living in an area with no sunlight.
Most living things on the planet depend upon sunlight directly or indirectly. Plants that live
on land use the energy of sunlight to make sugars and other chemicals, which provide food
for animals. Here is a simple example. A grasshopper eats shrubs that contain nutrients. A
mouse called a grasshopper mouse eats the grasshopper. A hawk swoops down and eats the
mouse. This is an example of a food chain. A food chain usually begins with a living thing
that can change the energy of sunlight into chemical energy, such as sugar molecules. In this
food chain example, the shrub is called a “producer”, because the plant makes food. The
grasshopper, mouse, and hawk are called “consumers” in the chain, because they eat a plant
or animal.
Similar food chains are found in parts of the oceans that receive sunlight. In ocean
water, tiny phytoplankton use sunlight to make sugars and other chemicals. “Phyto” means
“plant” and most of the phytoplankton are like very small plants. Tiny animals called
zooplankton eat phytoplankton (“zoo” means “animal”). Sardines and other small fish eat
zooplankton. Sharks and other large predators eat the small fish. In this example of a food
chain, sunlight is again vital. Sunlight enables producers to make nutrients. So, how can
animals survive without sunlight near hydrothermal vents?
Animals can live in the dark sea bottom, because chemosynthetic bacteria are
producers in a unique food chain. These bacteria use energy from chemical reactions to
make nutrients. The water that pours from the vents is rich in minerals and hydrogen
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sulfide. Instead of using the energy of sunlight to make nutrients, the bacteria use hydrogen
sulfide as an energy source to produce nutrients. The animals that live near a deep sea vent
are consumers. For example, shrimp graze on mats of bacteria that cling to rocks. A twofoot long white fish called a zoarcid fish eat the shrimp. A vent octopus eats the zoarcid
fish. In this example, the shrimp is a primary consumer, because it eats the producer,
bacteria.
A deep sea vent community can have many primary consumers that eat bacteria, such
as shrimp, mussels, and clams. Yet, not all primary consumers actually eat bacteria. Some
animals share a symbiotic relationship with bacteria. A symbiotic relationship is a close
association of different types of animals, which can benefit both animals.
Tube worms live near deep sea vents. These
Tube worms live near
animals are attached to the ocean floor and can grow
hydrothermal vents and
have a symbiotic
more than eight feet high. Vent tube worms have a
relationship with
chemosynthetic bacteria.
symbiotic relationship with bacteria. A vent tube
The bacteria enter their
worm does not have a gut. The spongy tissues inside
body when tubeworms
are young and have
the worm are full of bacteria that make nutrients for
mouths and guts. As
they grow, those features begin to disappear. Millions of
the worm. The top end of a tube worm has a red,
bacteria inside a tubeworm convert chemicals from
blood-filled plume with tiny tentacles that sway in the
hydrothermal vents into energy. Tubeworms grow and
reproduce quickly, due to the limited life-time of a
ocean currents. Chemicals from the water enter the
hydrothermal vent. When a hydrothermal vent goes out,
then the tubeworm cannot survive without the minerals.
plumes. As blood flows through the plumes, blood
proteins bind hydrogen sulfide from the water and carry the chemical to bacteria. The
bacteria use hydrogen sulfide to make chemical nutrients that the tube worm needs. In
addition to supplying hydrogen sulfide, the tube worm provides bacteria with a safe place to
live.
Since the discovery of deep sea vent animal communities in 1977, scientists have
found more than 300 new types of vent animals. The animals have one feature in common.
They all depend upon chemical-making bacteria.
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