Download hydrothermal vents and chemosynthesis

HYDROTHERMAL VENTS AND CHEMOSYNTHESIS:
A HABITAT IN THE DARK
Many of us are familiar with "Old Faithful" in Yellowstone National Park. This famous
geyser erupts several times a day. It spouts a column of water heated by volcanic rock deep
within the Earth's crust.
A hydrothermal vent is a geyser on the
seafloor, where it is very deep and very dark. They
are usually found in areas of volcanic activity. They
continuously gush super-hot, mineral-rich water that
supports a diverse community of organisms. Even
though we might consider this to be a harsh
environment, hydrothermal vents are abundant with
life. In fact, more than 300 species live around the
vents and are unique to this type of environment.
These creatures include tubeworms taller than you,
fish, crabs, shrimp, clams, and chemosynthetic
bacteria. These organisms have evolved to survive
in the complete darkness, the extremely hot vent
water and the tremendous water pressure.
A hydrothermal vent
Hydrothermal vents were discovered in 1977 in the Pacific Ocean. Since then, they have
been found in the Atlantic, Indian, and most recently, the Arctic Ocean. Most occur at an average
depth of about 2,100 meters (7,000 ft) in areas of seafloor spreading along the Mid-Ocean Ridge
system — the underwater mountain chain that winds around the globe.
How do hydrothermal vents form? In some areas along the Mid-Ocean Ridge, the huge
plates that form the Earth's crust are moving apart, causing deep cracks in the ocean floor.
Seawater seeps into these openings and is heated by the molten rock, or magma, beneath the
crust. As the water heats up, it rises (hot water is less dense than cold water!).
When this "hot spring" gushes out into the ocean, its temperature may be as high as
360°C (680°F)! Yet this water does not boil because it is under so much pressure from the
tremendous weight of the ocean above.
Hydrothermal vents are so deep that light is unable to penetrate. Without light, plants,
algae (seaweed) and phytoplankton are unable to perform the process of photosynthesis.
Therefore, photoautotrophs are unable to form the basis of the food chain as they do where light
is available. Organisms in hydrothermal vents must acquire energy in another way.
Before scientists had the technology to study hydrothermal vents, they believed that only
small animals lived at the ocean bottom. They thought that these animals received their food
from above, from organisms that depended on sunlight and photosynthesis, just as a food chain
on land does. Scientists knew that when plants and animals that live near the ocean’s surface
die, they sink to the bottom of the ocean. They assumed that this dead organic material would
then feed bottom-dwelling animals.
But this turned out not to be entirely true. With the
use of deep-sea submersibles, scientists have now
discovered vast communities of fairly large animals in the
dark depths! Instead of using light to create organic
material to live and grow (photosynthesis),
microorganisms at the bottom of the food chain near vents
used chemicals such as hydrogen sulfide
(chemosynthesis).
The Alvin, a deep-sea submersible
At the seafloor, thriving ecosystems receive energy
from a source that had never been thought of before - heat
and chemicals from the planet itself. The energy to sustain
life was not coming down from the sun. It was coming up
from the interior of the earth.
Animals at these depths depend on bacteria
that are able to use sulfur and other compounds
within vent discharge as energy sources to make
glucose, a process called chemosynthesis. Larger
animals then eat the chemosynthetic bacteria, or
eat the animals that eat the bacteria. In some cases,
the chemosynthetic bacteria live inside the bodies
of vent creatures in a symbiotic relationship.
Some organisms, such as tubeworms, that live
around the vents do not have a mouth or even a
digestive tract as we do. The bacteria actually live
inside their bodies and provide nutrients directly to
the organism’s tissues.
Adapted From:
http://www.onr.navy.mil/focus/ocean/habitats/vents2.htm
http://www.divediscover.whoi.edu/vents/index.html
http://www.ceoe.udel.edu/extreme2004/geology/hydrothermalvents/index.html
Crabs, Worms and Mussels in a
Hydrothermal Vent
HYDROTHEMAL VENTS PRE-READING
Root words
Meaning
New Vocabulary
hydro
hydrothermal
therm
chemo
chemosynthesis
photo
synthesis
photosynthesis
auto
photoautotroph
troph
sym
symbiotic
bio
Definition
Unfamiliar
term
Sentence
geyser
The shaken soda can
erupted like a geyser when
opened.
diverse
Nemo and his coral reef
friends represent a diverse
community.
abundant
The buffet table was filled
with an abundant amount
of dessert.
molten
I expect my molten
brownie dessert to be hot
and gooey!
submersible
A submarine is a
submersible ship.
Picture
Predicted
meaning
Definition
Unfamiliar
term
Sentence
microorganisms
I cannot see the
microorganisms living on
my skin.
sustain
Hurricane Sandy sustained
winds of 45 miles per hour
for 2 days.
compounds
Hydrogen and oxygen
make the compound water.
nutrient
Venus fly traps eat flies for
extra nutrients.
Picture
Predicted
meaning
Definition
HYDROTHEMAL VENTS ANALYSIS: PART I
1. Describe the environment around a hydrothermal vent.
2. List six (6) types of organisms that live near hydrothermal vents.
3. How are hydrothermal vents formed?
4. On land, there is usually plenty of sunlight. What organism
normally uses this sunlight to produce sugars (food and fuel)
for terrestrial food chains?
Producer Herbivore
Why are these organisms unable to survive near hydrothermal vents?
Carnivore
5. At the ocean’s surface, there is also usually plenty of sunlight. What organism(s) normally
use(s) this sunlight to produce sugars (food and fuel) for shallow water food chains?
Would you expect to find much of this growing near
hydrothermal vents? Why or why not?
Producer
Herbivore
Carnivore
6. In the deep ocean near hydrothermal vents, what organism produces sugars (food and fuel)
for these deep ocean food chains?
Describe in detail how this organism obtains energy.
7. Describe how organisms higher up the food chain (consumers) in hydrothermal vent
communities obtain energy.
PART II
CHEMOSYNTHESIS vs. PHOTOSYNTHESIS
Below is the chemical reaction that occurs during chemosynthesis. Remember that this reaction
is happening in the deep, dark ocean near the intense heat of hydrothermal vents.
Chemosynthesis
heat
6 CO2 + 6 H2O + 3 H2S
carbon dioxide
water

C6H12O6 + 3 H2SO4
hydrogen sulfide
glucose
1. What are the REACTANTS in chemosynthesis?
sulfuric acid
________________________
________________________
________________________
2. What are the PRODUCTS of chemosynthesis?
________________________
________________________
3. What form of ENERGY is used for chemosynthesis?
________________________
Below is the chemical reaction that occurs during photosynthesis. Remember that this reaction
requires sunlight.
Photosynthesis
light
6 CO2
carbon dioxide
+
6 H2O

water
4. What are the REACTANTS in photosynthesis?
C6H12O6
glucose
+
6 O2
oxygen
________________________
________________________
5. What are the PRODUCTS of photosynthesis?
________________________
________________________
6. What form of ENERGY is used for photosynthesis?
________________________
Using the reading and information you compiled in your worksheet answers,
complete the Venn diagram below comparing chemosynthesis to photosynthesis.
Photosynthesis
Chemosynthesis
Properties
unique to
chemosynthesis
Similarities between
chemosynthesis and
photosynthesis
Properties
unique to
photosynthesis
Items to include in your Venn diagram:
 reactants
 products
 energy sources
 types of organisms that perform these processes
 types of environments (aquatic/terrestrial/deep ocean) where these processes occur