# Presentation: 107977

## Life in “Extreme” Environments

**Life in “Extreme” Environments**
**in the Ocean***

**W. H. Berger**
**Scripps Institution of Oceanography**

***what is extreme to some may be perfectly normal to others and vice versa**

## Ridge Crest hot vents, giant tube worms and associated fauna. Sulfur-based.

**Ridge Crest hot vents, giant tube worms and associated fauna. Sulfur-based.**
**Continental margin cold vents. Bacterial mats and associated fauna. Carbon-based.**
**Bacteria and Archea in general, in organic-rich environments.**
**Sulfide producers and –oxidizers.**
**Methane producers and –oxiders.**

## Principle: reaction of seawater with hot basalt strips oxygen from sulfate dissolved in seawater and this produces hydrogen sulfide.

**Bacteria gain energy from oxidizing the hydrogen sulfide, which leads to proliferation of these organisms in places where these two substances meet.**
**The bacteria then become the base for a “chemosynthetic” food chain, by being grazed and filtered out of the water and by functioning, in cases, as internal symbionts.**

**Hot Vent Environment:**
**  **

## Common misconception: this food chain has no connection to solar energy, being supported by internal Earth heat.

**In fact: the presence of free oxygen in the water (for oxidizing the hydrogen sulfide) is due to uptake of oxygen from the air, and the presence in the air owes to the burial of reduced carbon and therefore to photosynthesis.**

## Slide 5

## Slide 6

## The giant tube worms (East Pacific Rise) have no digestive system - no mouth or gut. 

- The giant tube worms (East Pacific Rise) have no digestive system - no mouth or gut.
- The worm depends largely on symbiotic bacteria for its nutrition.
- The brown, spongy tissue filling the inside of a tube worm is packed with bacteria - about 285 billion bacteria per ounce of tissue.

## Cold Seep Environment:

**Archea and bacteria gain energy from oxidizing methane and hydrogen sulfide, which leads to proliferation of these organisms.**
**The archea and bacteria then become the base for a “chemosynthetic” food chain, presumably both by being grazed and filtered out of the water and by functioning as symbionts.**

**Cold Seep Environment:**
**  **

## Common misconception: this food chain has no connection to solar energy, being supported by internal Earth heat.

**In fact: both methane and hydrogen sulfide are formed as a result of reactions involving organic carbon (buried in the margins). Thus, they are a product of photosynthesis, as is the presence of free oxygen in the water.**

## Arctic Ocean methane seeps with archeal mats. Barents Sea.

## Gas hydrate carbonates

## Gas hydrate dredged from the sea floor

## Methane archea and sulfur bacteria have become a new focus of investigation, because of their ability to make a living in environments that are “strange” to the rest of the organic world.

**Especially interesting:**
**Sulfur-processing bacteria can be extremely large.**
**Methane-processing archea can mean big trouble for humankind.**

## Mats of conspicuous sulfur bacteria belonging to the genus Beggiatoa have been found in Monterey Canyon cold seeps.

**Mats of conspicuous sulfur bacteria belonging to the genus Beggiatoa have been found in Monterey Canyon cold seeps.**
- Individual disk-shaped cells, roughly 75 micrometers in diameter, form filaments one to several centimeters long.
- These bacteria have been recently described as sulfur oxidizing, nitrate respiring autotrophs that contain a central vacuole accounting for roughly 80% of the cellular biovolume. Nitrate is concentrated 400~fold over ambient concentration and is presumably stored in the vacuole. In these traits, as well as the extraordinary biomass achieved in surficial marine sediments, these Beggiatoa filaments show striking parallels with those of the extensive Thioploca mats found off the western coast of South America. Ribosomal RNA sequence analyses of Beggiatoa spp and Thioploca spp. support the  view that the nitrate-accumulating, vacuolate phenotype is monophyletic.

- S. C. McHattont, A. Ahmad, J. P. Barry and D. C. Nelson
- University of California, Davis, and MBARI, Moss Landing.

## Beggiatoa alba

***Beggiatoa alba***
***http://www-cyanosite.bio.purdue.edu/images/images.html***

## The biggest ever: Thiomargarita namibiensis

- One hundred times bigger than the next largest
- Essentially: hollow space filled with nitrate, for storing oxygen to process hydrogen sulfide
- From Namibia upwelling system: extremely high productivity

## Methane is produced in copious amounts within organic-rich sediments in the continental margins.

- At high concentrations,
-  low temperatures and
- high pressures, methane
- ice can form.

## Methane ice burns if ignited, as it melts

## Ice worms, growing on methane ice in the Gulf of Mexico

- Live with archeal symbionts

## Most of the hydrate is on the upper continental slope, because that is where organic-rich sediments are.

- The water has to be cold for this ice to be stable.

## On land, methane ice is stable in permafrost regions

**On land, methane ice is stable in permafrost regions**

## The distribution of methane ice can be traced by the “bottom simulating reflector” produced at the boundary between gas and ice. The ice forms as a roof over the archeally generated gas-rich interstitial fluids.

## Methane clathrates are widespread in the ocean and also occur in some freshwater bodies.

## Take-home message

- Archea have created a time-bomb deep in the sediments of the continental slope.
- Their activities can be observed from space, when “gas volcanoes” emit methane and associated hydrocarbons producing slicks on the surface of the sea. This information is used by oil companies to find promising places to drill for gas and petroleum.