1. Life in Extreme Environments
- Hot Vents
- Cold Seeps
- Brine Pools
Reading:
4th Ed: Ch 16 Sec 18, Ch 4 Sec 14, Ch 14 Sec 2
5th Ed: Ch 16 Sec 19, Ch 4 Sec 14, Ch 13 Sec 4
Graphic: Submersible exploring a brine pool. Penn. State Univ.
2. The Deep Sea
The deep sea is cold and dark
- The food web is weakly supported by organic matter raining from above
- Photosynthetic production of new organic matter is not possible due to lack of
light
Most deep sea communities are adapted to
- sparse food availability
- low population density
Graphics (top) Rat-tail, S.Ross photographer, (bottom) octopus, L.Levin,
photographer. Both courtesy of NOAA NURP.
3. Alternative Energy in the Deep Sea
But… Not all ecosystems are fueled by photosynthesis
Methane and sulphur-rich fluids provide energy for chemosynthetic bacteria in
some deep sea communities
Graphic: Black smoker at a mid-ocean ridge hydrothermal vent. P.Rona
photographer, courtesy of NOAA NURP.
4. Chemosynthesis (An Old Way of Life)
Chemosynthesis synthesizes organic material from inorganic substances
Carbon + Hydrogen + Oxygen + Water Carbohydrates + Sulfuric Acid
Dioxide Sulfide
Chemosynthesis can sustain vibrant food webs in the complete absence of sunlight
Graphic: Tubeworms and mussels living on a methane hydrate mound (yellowish
substance). Courtesy of NOAA Ocean Explorer.
5. Photosynthesis vs. Chemosynthesis
Graphic: Courtesy of NOAA, PMEL.
6. Where Are Chemosynthetic Communities Found?
Chemosynthesis requires high concentrations of chemicals such as hydrogen
sulfide or methane
These are found where:
- seawater is in contact with the mantle (hydrothermal vents)
- these materials enter the sea due to other processes (cold seeps and brine
pools)
Graphic: Garrison, 4th Ed., Fig. 16.19, pg 431, 5th Ed., Fig. 16.20, pg 408.
7. What is a Hydrothermal Vent?
Hydrothermal vents eject hot, mineral and gas-rich fluids into the ocean at
active seafloor spreading sites along mid-ocean ridges
Graphic: Garrison, 4th Ed., Fig. 4.25, pg 112, 5th Ed., Fig. 4.26 pg 104.
8. Hydrothermal Vent Communities
At hydrothermal vents and cold seeps, chemosynthetic bacteria are at the base of
complex food webs
Other organisms:
- tube worms
- giant clams
- mussels
Graphic: Tube worms feeding near the base of a black smoker hydrothermal vent.
Courtesy of National Undersea Research Program.
9. Challenges in a Hydrothermal Vent Community
Most inhabitants must be adapted to life at high temperatures (sometimes over
600 deg F!)
Hydrothermal vents are transient features – organisms must be able to colonize
distant locales
Graphics: (left) See Garrison, 4th Ed. Fig. 16.20a, 5th Ed., Fig. 16.21, (right)
courtesy of NOAA Ocean Explorer.
10. Cold Seep Environments
Tectonic motion can force methane-rich fluids out of sediments to form cold
seeps along continental margins
Cold seeps emit chemical-rich fluid slowly over long periods of time
Unlike hydrothermal vents, these are relatively stable environments, home to
long-lived organisms
Graphic: Tube worms in a Gulf of Mexico cold seep grow to 2 meters long,
C.Fisher, photographer, courtesy of NOAA NURP and Penn. State Univ.
11. Cold Seep Communities
In many cold seeps, the food web is supported by:
- “mat” forming bacteria
- bacteria that are in symbiotic relationships with animals
Clams and worms derive most of their food from the bacteria
Other animals forage at the seeps (crabs, anemones, gastropods)
Graphic: Mussels, worms and a spider crab at a hydrocarbon seep, I.MacDonald,
photogapher. Courtesy of NOAA NURP and Texas A&M Univ.
12. Brine Pools
Along passive margins, salt domes can create brine pools with salinity 4 times
greater than seawater
Methane seeping from the edges of the pool creates a diverse community
But.. anything that swims or falls into the hypersaline pool dies
Graphic: (top) Edge of a brine pool, a super salty pond, ringed by mussels. J.
Brooks, photographer, courtesy of NOAA NURP and Texas A&M Univ, (bottom)
submersible exploring a brine pool, Penn. State. Univ.
14. The Brine Pool
The brine pool is a crater-like depression filled with water up to four times
saltier than seawater
Mussels and other organisms inhabit the region just outside the pool
Graphic: Gulf of Mexico brine pool. Image based on mosaic from Dr. I.McDonald,
Texas A&M Univ.
15. Extreme Environments - A Model for Extraterrestrial Life?
Hydrothermal vent communities suggest life could be thriving elsewhere in our
solar system
Europa (a moon of Jupiter)
- icy surface
- deep saltwater ocean
- tectonic activity
- hydrothermal vents??
- life???
Graphics: (top) Europa as viewed by Voyager I, (bottom) Europa's icy surface, as
viewed by Galileo, both courtesy of NASA/JPL.
16. Preview of Next Lecture
Sustainable Seas - Marine Fisheries
Reading:
4th Ed: Ch 17 Sec 1, 15-18, Ch 9 Sec 13, Ch 14 Sec 15
5th Ed: Ch 17 Sec 1, 17-20, Ch 9 Sec 13, Ch 14 Sec 11
Graphic: Fishing in the Eastern Atlantic. J.Prado, photographer, courtesy of
NOAA.