Introduction: Chemosynthesis at Hydrothermal Vents
The fluid that ‘vents’ out of the hydrothermal vent chimneys is rich in chemicals. As the
seawater is heated by magma below the vent field, some chemicals are transferred to the
water from the hot crust material. Some of these metals precipitate out of the fluid as it
rises, forming the vent chimneys, while other minerals mix with surrounding waters.
Bacteria, or microbes, living on or around the hydrothermal vent use these chemicals for
chemosynthesis, the process that makes food from inorganic compounds.
Vent chemicals for chemosynthesis:
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Vent image: Courtesy of the NOAA Ocean Exploration, 2016 Deepwater Exploration of the Marianas.
Vent diagram: Image modified from Massoth et al., 1988; courtesy of Submarine Ring of Fire 2002, NOAA Ocean Exploration.
1. Read through the following organism cards to learn more about several of the organisms
that make up a hydrothermal vent community.
2. Using the information on the cards, create a food chain that includes four of the organism
cards.
a. Drag four of the organism cards on slide 17 to form a food chain (move the extra cards off to the
side by dragging them out of the way).
Hint: You should end up with one organism in each trophic level on slide 19.
b. Draw arrows between the organism cards to show the direction that energy is flowing through the
food chain.
3. Hydrothermal vent food webs are far more complex than a simple food chain. Now, use all
of the organism cards to complete the food web template on slide 18.
a. Type the name of each organism in the empty boxes provided.
b. Draw arrows to show the direction that energy is flowing through the food web.
Hint: Some organisms will eat or be eaten by more than one organism!
Activity Instructions (digital version, option 1)
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1. Read through the following organism cards to learn more about several of the organisms that
make up a hydrothermal vent community.
2. Using the information on the cards, create a food chain that includes four of the organism cards
on slide 17.
a. Copy the four organisms you wish to use from slide 17 and paste onto slide 19.
b. Arrange the organism cards to form a food chain.
Hint: You should end up with one organism in each trophic level on slide 19.
c. Draw arrows between the organism cards to show the direction that energy is flowing through the food chain.
3. Hydrothermal vent food webs are far more complex than a simple food chain. Now, use all of the
organism cards on slide 17 to create a food web.
a. Copy all of the organism cards from slide 17 and paste onto slide 19.
b. Arrange the organism cards by dragging them into the appropriate trophic levels on slide 19 to form a food web.
c. Draw arrows between the organism cards to show the direction that energy is flowing through the food chain.
Hint: Some organisms will eat or be eaten by more than one other organism!
Activity Instructions (digital version, option 2)
3
H
2
S
Hydrogen Sulfide
CO
2
Carbon Dioxide
O
2
Oxygen
CH
4
Methane
Hydrothermal Vent Chemicals
4
These free-swimming microbes have four long flagella (tails) that help
propel them through the water. These bacteria are also able to form
bacterial mats that appear stringy or wispy in texture.
The bacteria are chemosynthetic. They oxidize hydrogen sulfide, add
carbon dioxide and oxygen to produce sugar (food), sulfur, and water. The
food that chemosynthetic bacteria produce serves as the base of the
hydrothermal vent food web.
Vent Bacteria, Arcobacter sulfidicus
5
Top: Image courtesy of Submarine Ring of Fire 2002, NOAA Ocean Exploration.
Bottom: Image adapted from “New Vent Site” video. Courtesy of NOAA Ocean Exploration, Galapágos Rift Expedition 2011.
Symbiotic vent bacteria are found inside the tissues of other vent
animals, such as tubeworms or mussels.
The bacteria are chemosynthetic. They oxidize hydrogen sulfide, add
carbon dioxide and oxygen to produce sugar (food), sulfur, and water.
The food that chemosynthetic bacteria produce serves as the base of the
hydrothermal vent food web.
The food the bacteria makes is shared with the host organism, and
in return the bacteria has a safe home.
The image to the left shows two symbiotic microbes found living
inside the tissues of vent mussels.
Symbiotic Bacteria
6
Mussels: Image courtesy of Submarine Ring of Fire 2004, NOAA Vents Program.
Bacteria: Image courtesy of Fisher et. al, Marine Ecology 1993.
Zooplankton are microscopic animals that drift in the
ocean. At hydrothermal vents, they usually include the
larval forms of several species found near vents, like
crabs, shrimp, worms and snails.
These larval forms may drift in the water column for
days to months before settling back to the bottom, and
are the main means by which new vent sites are
colonized.
Here, zooplankton consume bacteria living at the vents.
Vent Zooplankton
7
Image courtesy of Submarine Ring of Fire 2014 - Ironman, NOAA/PMEL.
These small shrimp are well adapted for living in the
extreme conditions of a hydrothermal vent. They
are capable of surviving very high temperatures.
Some species are blind. Instead of eyes, these
species have specialized heat sensing organs on
their backs that help them “see” the surrounding
environment.
Some species of vent shrimp feed directly on the
bacterial mats growing on and around vent
chimneys for their entire life, while others only feed
on the bacteria during early life stages.
Vent Shrimp
8
Image courtesy of Submarine Ring of Fire 2014 - Ironman, NOAA/PMEL.
Vent mussels attach to vent chimneys and surrounding rocks using
byssal threads, or very sticky filaments produced by the mussels’ foot.
The mussels are often found growing in large clusters. The black spots
on the shells are former anchor points of mussels who have cut their
threads and moved on.
The small gaps between mussels in a cluster are used by other small
vent invertebrates like worms or shrimp.
Vent mussels have chemosynthetic bacteria that live inside their gills.
The bacteria make food for the mussels by converting inorganic
materials into sugars. They are also capable of suspension feeding.
Some species of mussels have more than one type of symbiont in their
gills, allowing them to derive energy from different inorganic
compounds, such as methane or hydrogen sulfide.
Vent Mussel, Bathymodiolus sp.
9
Image courtesy of Submarine Ring of Fire 2004, NOAA Vents Program.
Tubeworms do not have a mouth, gut, or anus. They completely lack a digestive
system!
Instead of "eating," these animals get their food from special symbiotic bacteria
that live within their body in an organ called the trophosome. It is estimated that
one tubeworm is host to billions of these chemosynthetic bacteria.
The white tube acts as the outer skeleton for the worm. This can grow over 1 meter
(3 feet) in length.
The red plume is bright red in color due to high blood flow. The blood carries
important compounds from the water, like oxygen, to the symbionts living inside.
The image to the left appears blurry due to the extremely hot water “venting” out of
the vent field, which distorts the image.
Riftia Tubeworm, Riftia pachptyla
10
Image adapted from “New Vent Site” video. Courtesy of NOAA Ocean Exploration, Galapágos Rift Expedition 2011.
Squat lobsters are small crustaceans that roam about the
vent ecosystem. They have very long claws. Some species
have claws twice as long as their body.
The squat lobsters in this photo appear “hairy” due to the
bacteria growing on their shells.
They are scavengers that feed on bacteria mats, small
zooplankton, amphipods, and other vent debris.
Squat Lobsters (Galatheid Crabs), Munidopsis alvisca
Image courtesy of Submarine Ring of Fire 2014 - Ironman, NSF,
NOAA, Jason, copyright WHOI.
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Siphonophores are actually comprised of many
individuals that all work together. Some individuals
protect the colony, some catch food, and some
reproduce. They are a type of cnidarian, closely related to
corals, sea anemones, and jellyfish.
Dandelion siphonophores are usually observed anchored
to seafloor using their tentacles. This animal was
observed at approximately 2,530 meters (8,300 feet)
depth, with its feeding tentacles extended around the
animal like a spider web. All siphonophores are predatory
carnivores believed to feed on copepods, and other small
crustaceans like crabs and krill.
Dandelion Siphonophore
12
Image courtesy of the NOAA Ocean Exploration, 2017 Laulima O Ka Moana.
These long, slender white fish grow up to two feet
(61 centimeters) in length. They are quite slow
and lethargic. They spend a lot of time floating
around clumps of tubeworms and mussels.
Despite their sluggish behavior, they have huge
appetites. Eelpouts are predators that feed on
everything from tubeworms to shrimp.
Eelpout (Zoarcid Fish), Pachycara gymninium
13
Image adapted from “New Fish Species” video. Courtesy of NOAA Ocean Exploration,
2016 Deepwater Exploration of the Marianas.
Ratfish, also known as a chimaera, have long,
tapered tails and short, rounded snouts.
Like sharks, ratfish are cartilaginous, and have no
real bones. The prominent lateral line that runs
down their side is full of mechanoreceptors that
detect pressure waves, similar to human ears.
The vent ratfish is a carnivore and feeds on a
variety of animals smaller than itself. It eats
crabs, shrimp, smaller fish, and vent mussels.
Vent Ratfish (Chimaera), Hydrolagus affinis
14
Image adapted from “Chimaera” video. Courtesy of NOAA Ocean Exploration,
2016 Deepwater Exploration of the Marianas.
Crabs are scavengers and these blind vent
crabs are known to feed on shrimp,
mussels, tubeworms as well as each other.
Blind Crab
Image courtesy of Schmidt Ocean Institute
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Octopods are very active, carnivorous
molluscs. They have eight arms lined
with suction cups that help them catch
prey and they hide in small crevices
around the vents.
Certain species of octopods eat many
smaller animals in the vent ecosystem
such as crabs, shrimp, and mussels.
Octopus
16
Image adapted from “Octopus” video. Courtesy of NOAA Ocean Exploration,
Galapágos Rift Expedition 2011.
Vent
Bacteria
Symbiotic
Bacteria
Vent
Shrimp
Vent
Mussel
Squat
Lobster
Octopus
Riftia
Tubeworm
Eelpout
Ratfish
Vent
Chemicals
H
2
S C0
2
0
2
CH
4
Blind Crab
Dandelion
Siphonophore
Zooplankton
Hydrothermal Vents: Organism Cards
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Simple
Chemicals
Primary
Producers
Primary
Consumers
First Order
Carnivores
Top Order
Carnivores
H
2
S
C0
2
0
2
CH
4
Read through the organism cards above. Fill in the hydrothermal vent
food web below by typing in the organism’s name where it belongs.
Draw arrows between the organisms to show what direction the
energy flows through the food web and “who eats who.”
Hydrothermal Vent: Food Web
(Option 1)
18
Simple
Chemicals
Primary
Producers
Primary
Consumers
First Order
Carnivores
Top Order
Carnivores
H
2
S
C0
2
0
2
CH
4
Read through the organism cards above. Copy and paste the
organism cards on slide 17 below. Create a food web by arranging the
organism cards into the categories below. Draw arrows between the
organisms to show what direction the energy flows through the food
web and “who eats who.”
Hydrothermal Vent: Food Web
(Option 2)
19
Hydrothermal Vent: Food Web (Answer Key)
20
Image Hyperlinks
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SLIDE 2
Vent: https://oceanexplorer.noaa.gov/okeanos/explorations/ex1605/logs/photolog/welcome.html#cbpi=/okeanos/explorations/ex1605/dailyupdates/media/may2.html
Diagram: https://oceanexplorer.noaa.gov/explorations/02fire/background/vent_chem/media/chemistry.html
SLIDE 5 (Vent Bacteria)
Top: https://oceanexplorer.noaa.gov/explorations/02fire/logs/jul29/media/anhydrite.html
Bottom: https://oceanexplorer.noaa.gov/okeanos/explorations/ex1103/logs/photolog/welcome.html#cbpi=/okeanos/explorations/ex1103/dailyupdates/media/video/0723-vent-site.html
SLIDE 6 (Symbiotic Bacteria)
Mussels: https://oceanexplorer.noaa.gov/explorations/04fire/logs/april11/media/grazers_600.jpg
Bacteria: https://oceanexplorer.noaa.gov/explorations/06mexico/logs/may20/may20.html
SLIDE 7 (Vent Zooplankton): https://oceanexplorer.noaa.gov/explorations/04fire/logs/april14/april14.html
SLIDE 8 (Vent Shrimp): https://oceanexplorer.noaa.gov/explorations/14fire/background/seamounts/media/eifuku_mussels4_hires.jpg
SLIDE 9 (Vent Mussel): https://oceanexplorer.noaa.gov/explorations/04fire/logs/april11/media/grazers_600.jpg
SLIDE 10 (Riftia Tubeworm): https://oceanexplorer.noaa.gov/okeanos/explorations/ex1103/logs/photolog/welcome.html#cbpi=/okeanos/explorations/ex1103/dailyupdates/media/video/0723-vent-site.html
SLIDE 11 (Squat Lobsters): https://oceanexplorer.noaa.gov/explorations/14fire/logs/december08/media/mussels_lobsters_hires.jpg
SLIDE 12 (Dandelion Siphonophore): https://oceanexplorer.noaa.gov/okeanos/explorations/ex1706/logs/july30/welcome.html
SLIDE 13 (Eelpout): https://oceanexplorer.noaa.gov/okeanos/explorations//ex1605/logs/photolog/welcome.html#cbpi=/okeanos/explorations/ex1605/dailyupdates/media/video/0707-fish/0707-fish.html
SLIDE 14 (Vent Ratfish): https://oceanexplorer.noaa.gov/okeanos/explorations/ex1605/dailyupdates/media/video/0504-chimaera/0504-chimaera-1920x1080.mp4
SLIDE 15 (Blind Crab): https://schmidtocean.org/cruise-log-post/animal-life-mariana-back-arc/
SLIDE 16 (Octopus): https://oceanexplorer.noaa.gov/okeanos/explorations/ex1103/logs/photolog/welcome.html#cbpi=/okeanos/explorations/ex1103/dailyupdates/media/video/0721-octopus.html
