Transcript Activity 3 Tubeworm Mystery Powerpoint

FLEXE Great Tubeworm Mysteries
How can animals like the giant tubeworm exist in the cold dark seafloor?
FLEXE Great Tubeworm Mysteries
Tubeworms were first discovered at Mid-Ocean Ridges
Locations of Mid-Ocean Ridges
(Image from U.S. Geological Survey)
FLEXE Great Tubeworm Mysteries
Mid-Ocean Ridge Processes
Spreading Centers
Ocean Bottom
(Image from Dive and Discover, WHOI)
FLEXE Great Tubeworm Mysteries
Global distribution of known hydrothermal vent sites
(Image from Van Dover et al. 2002)
FLEXE Great Tubeworm Mysteries
How hydrothermal vents form
Deep Ocean Seawater
Seafloor
(Image from Dive and Discover, WHOI)
FLEXE Great Tubeworm Mysteries
Potential challenges:
• No light
• Very high pressure
• Low temperatures
• Very little food
• New seafloor
Scientists expected to find very little life at vents
FLEXE Great Tubeworm Mysteries
But THIS is what they found instead!
What are these animals eating?
FLEXE Great Tubeworm Mysteries
And so began
the Great Tubeworm Mystery…
Before you begin to solve the mystery,
let’s look at what scientists did know
about the vent environment.
FLEXE Great Tubeworm Mysteries
Bacteria are everywhere!!
(Image courtesy of Dr. Joe Resing and WHOI)
FLEXE Great Tubeworm Mysteries
Some bacteria can perform chemosynthesis
Chemosynthesis:
Photosynthesis:
Reduced chemical (often sulfide, HS-)
Photon
Energy
Chemical
Energy
Oxidized chemical
CO2 + H2O  sugars + O2
CO2 + H2O  sugars + O2
FLEXE Great Tubeworm Mysteries
But back to the tubeworms
Mystery:
How do the tubeworms obtain nutrition?
Hypothesis #1:
Tubeworms are eating free-living bacteria to obtain energy.
FLEXE Great Tubeworm Mysteries
Basic Tubeworm Anatomy
No Mouth
But how can
they eat with no
mouth, gut, or
anus?
No Anus
No Digestive Tract
FLEXE Great Tubeworm Mysteries
Lines of evidence - #1
Basic Tubeworm Anatomy
Plume
Dr. Colleen Cavanaugh used
microscopy techniques in 1981
and discovered billions of
bacterial cells packed inside
the tubeworm’s trophosome.
Trophosome
1011 bacteria per gram of trophosome!!
FLEXE Great Tubeworm Mysteries
Lines of evidence - #2
Also in 1981, Dr. Horst Felbeck discovered Rubisco, the same enzyme
plants use in the Calvin Cycle in photosynthesis, in the tubeworm.
CO2
INPUT =
inorganic
carbon
Rubisco
Calvin
Cycle
Sugar
enzymes
and
chemical
reactions
OUTPUT =
organic carbon
FLEXE Great Tubeworm Mysteries
H2S from vent
fluids
Tubeworm + bacteria = Symbiosis!
1. Tubeworm takes up
hydrogen sulfide (H2S),
carbon dioxide (CO2) and
oxygen (O2) using its plume
and shuttles these chemicals
to its trophosome
CO2 and O2
from
seawater
2. Bacteria in
trophosome use
H2S, CO2, and O2 to
make sugars via
chemosynthesis
3. Sugars from
bacteria are used
as food by
tubeworm
FLEXE Great Tubeworm Mysteries
The Mystery Continues …
Mystery:
What about tubeworms found at cold seeps?
Hypothesis #2:
Seep tubeworms obtain energy in the same way as vent
tubeworms.
FLEXE Great Tubeworm Mysteries
Cold seeps support lush communities
Scientists assumed that seep tubeworms would obtain their energy
the same way vent tubeworms do because:
1. Seep tubeworms have plumes
2. Seep tubeworms have trophosomes packed full of bacteria that
use sulfide as an energy source
FLEXE Great Tubeworm Mysteries
Energy sources in the Gulf of Mexico
Sulfate in
seawater
Seep tubeworm
community
Bacteria in the sediment
use the energy obtained by
oxidizing methane to
create sulfide from sulfate
sulfide methane
Hydrocarbons
(Methane)
Ocean
Sediment
layer
Rock
(shale)
layer
Salt
layer
FLEXE Great Tubeworm Mysteries
Sulfide measurements around tubeworms
Levels of Sulfide (H2S) at Cold Seeps
Plume level: No sulfide
(0 µM H2S)
Height of
tubeworms =
~ 1 meter
Mid-level: Very low sulfide
(0 - 0.5 µM H2S)
Sediment level: Low sulfide
(0 - 1 µM H2S)
In the sediment: Very high sulfide
(100 - 1,000 µM H2S)
levels
FLEXE Great Tubeworm Mysteries
The Mystery Continues …
Mystery:
How do seep tubeworms take up sulfide?
Hypothesis #3:
What do you think???
FLEXE Great Tubeworm Mysteries
Mystery Solved!
These tubeworms have ‘roots’!
(well, not true roots, but extensions of their bodies that look and act like roots)
2. Sulfide is then
transferred to the
symbiotic bacteria in
the trophosomes of the
tubeworms
In the sediment:
Very high sulfide levels
(100 - 1,000 µM H2S)
1. Sulfide from the
sediment is taken up by
the tubeworm extensions
(‘roots’)