Transcript Hydrothermal Vents

Hydrothermal Vents:
Frontiers in Ocean Discovery
Background biology

Prior to 1977, biologists
thought that without
the energy of sunlight
to support a food
chain, organisms in the
deep sea ate only what
debris fell from surface
waters. Scarce food
meant that organisms
were few and far
between.
photograph by the Institute of Oceanographic Sciences, Deacon
Laboratory, Wormley, England
Background geology

Geologists knew that cold
water sunk into cracks in the
ocean floor and
hypothesized that this water
was heated beneath the
ocean crust. During heating,
the hot water would dissolve
minerals from surrounding
rocks. The heated, mineralladen water, hypothesized
geologists, would rise from
the seafloor at a vent.
Geologists test a hypothesis

In order to test their
hypothesis, geologists decided
send remote-controlled
equipment to look for vents
where oceanic plates pulled
away from each other at the
Galapagos Rift.

Since the temperature of the
deep sea varies very little from
35.6 degrees Farenheit,
geologists searched for small
changes in temperature.
Geologists find a vent!

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After temperature-sensitive equipment returned small
temperature changes at one site along the Rift, cameras
were sent to the same site and returned with pictures of
heaps of clam shells.
Repeated submarine dives to the same site revealed temperatures as
high as 46.4 degrees and a variety of unusual organisms.
The reaction of biologists

Biologists were astonished at the density of deep sea
life in vent areas. What did all of these organisms
eat? Were they related to the deep sea organisms
biologists already knew about?
Teeming vent shrimp
The unusual vent life forms were different from any
others recorded by scientists to date. A new age in
deep sea biology and ecology had begun!
Spaghetti worms
What is a hydrothermal vent?

At a hydrothermal vent, sea water that
has sunken into cracks in the ocean crust
and been heated (sometimes to over 180
degrees Farenheit!) by the interior of the
earth escapes through crust cracks back
into the ocean.

Superheated water beneath the oceanic
crust often dissolves minerals from nearby
rocks. As hot vent fluids meet cold ocean
water, minerals precipitate out of vent
fluids.

Precipitating minerals
often give vent fluids
different colored
“smoky” appearances.
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Precipitating minerals
can fall out of vent
fluids to form
“chimneys”(like the one
on the left) and other
formations on the sea
floor.
Without sunlight, how does a vent food web begin?

In areas of the earth that receive sunlight or are near areas that
receive sunlight, photosynthesizing plants are the basis of the food
chain. Using the energy of the sun, plants turn water and carbon
dioxide into carbohydrates. Carbohydrates are energy for plants and
for the organisms who eat plants.
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Bacteria are the green plants of hydrothermal vents. Through a
process known as “chemosynthesis”, bacteria use the energy in
hydrogen sulfide dissolved in vent
fluids to join water and carbon
dioxide into carbohydrates. Vent
communities food chains are based
on these bacteria!
Who else is in the food web besides
bacteria?
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Most deep sea animals can not tolerate the chemicals or hot
temperatures near vents. Vent animals are unique because
they can withstand and even thrive upon conditions that kill
most life. Some vent animals are related to more familiar
organisms, but some, like the fluffy ball that vaguely resembles
a dandelion, are not..

Grazing vent animals include snails, crabs, and limpets. These
animals graze on bacteria. Suspension feeders such as mussels,
barnacles, and feather-duster worms remove food from the
water. One kind of predator is the anemone. Anemones
capture prey with their tentacles. White crabs and brittle stars
are examples of scavengers that eat whatever live or dead
animals and bacteria they can find
Mussels
Feather-duster worms
How are vents populated?

Vents are often far apart. They often exist for just a few decades or
years. New vents are populated very quickly.
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Vent bacteria live in deep ocean water and in pores of deep ocean rocks
all of the time in low numbers. When a vent pops up, bacteria
populations flourish.
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Hot water streaming out of vents often plumes for 200 meters above the
sea floor because it is less dense than surrounding cold water. Plumes
probably carry larva into nearby currents. However, this still may not
account for the great distances between vents. Scientists continue to
test other hypotheses that consider “stepping stones”, or intermediate
sites, where vent animals may grow without a vent and release larvae.
Tube worms and giant white clams
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Tube worms and giant white clams are unique because they do not have
a digestive tract. They have no way of “eating” food. Both organisms
harbor symbiotic bacteria. The worms and clams transfer hydrogen
sulfide and oxygen to a special area of their body filled with bacteria.
Through chemosynthesis, the bacteria make carbohydrates to fuel
themselves as well as their larger hosts.
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Where are the vents and how many are there?
Nobody knows how many vents exist or where they all are.
Hydrothermal vents are constantly being formed and destroyed, and
many parts of the deep sea floor have yet to be seen by human eyes.
Some of the known sites are marked on the map below. Most occur on
or near boundaries between tectonic plates.