Armored Amoebas

Foraminifera, usually called forams, are nicknamed "armored amoebas." They are "armored" by tests—tiny shells that protect the single-celled creatures.

These protists live in all the world's oceans as drifting plankton or stationary benthic species. Forams are a key part of marine food webs.

Forams have survived for millions of years, successfully adapting to radical climate change in their marine habitat.

Carbon emissions that contribute to global warming, the current period of climate change, are putting a new stress on forams. As more carbon dioxide dissolves in the ocean, the water becomes more acidic. Ocean acidification makes it more difficult for forams to create tests, which they need to survive.
- Many foram tests are calcium carbonate, the same substance as clam shells, eggshells, and snail shells.
- Foram tests can also be "agglutinated sediment particles." Agglutinated just means the tests are made of sediment (such as grains of sand) "glued" together by the foram.
- The largest foram—a species called Syringammina—grows to a whopping 20 centimeters (8 inches). It is the largest single-celled organism in the world.
- Despite their appearance, forams are more closely related to algae and slime molds than snails or clams.
- Forams are one of very few creatures that can survive in the Challenger Deep, 10,898 meters (35,756 feet) below the ocean surface. More than 400 forams thrive in this very cold, very dark ocean trench, where the pressure is more than 111 megapascals (16,000 pounds per square inch).
Articles & Profiles
- National Geographic News: Life is Found Thriving at Ocean’s Deepest Point
- New York Times: ‘Nature’s Masons’ Do Double Duty as Storytellers
Websites
- University College London: MIRACLE—Foraminifers

Term	Part of Speech	Definition	Encyclopedic Entry
acid	Noun	chemical compound that reacts with a base to form a salt. Acids can corrode some natural materials. Acids have pH levels lower than 7.
adapt	Verb	to adjust to new surroundings or a new situation.
amoeba	Noun	one-celled, shapeless organism (protozoan).
armor	Noun	protective covering.
benthic	Adjective	having to do with the bottom of a deep body of water.
carbon dioxide	Noun	greenhouse gas produced by animals during respiration and used by plants during photosynthesis. Carbon dioxide is also the byproduct of burning fossil fuels.
carbon emission	Noun	carbon compound (such as carbon dioxide) released into the atmosphere, often through human activity such as the burning of fossil fuels such as coal or gas.
cell	Noun	smallest working part of a living organism.
climate change	Noun	gradual changes in all the interconnected weather elements on our planet.	Encyclopedic Entry: climate change
dissolve	Verb	to break up or disintegrate.
food web	Noun	all related food chains in an ecosystem. Also called a food cycle.	Encyclopedic Entry: food web
foraminifera	Plural Noun	(singular: foraminifer.) Type of microscopic organism (protist) that forms a shell and lives in marine or salty conditions.
global warming	Noun	increase in the average temperature of the Earth's air and oceans.	Encyclopedic Entry: global warming
habitat	Noun	environment where an organism lives throughout the year or for shorter periods of time.	Encyclopedic Entry: habitat
ocean acidification	Noun	decrease in the ocean's pH levels, caused primarily by increased carbon dioxide. Ocean acidification threatens corals and shellfish.
plankton	Plural Noun	(singular: plankton) microscopic aquatic organisms.
protist	Noun	type of microscopic organism (not an animal, plant, or fungus).
radically	Adverb	completely or extremely.
stress	Verb	to strain or put pressure on.
test	Noun	hard, protective shell or covering of some organisms.

Credits

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Photographers

Jessica Spear, courtesy U.S. Geological Survey
Todd Jacobs
James Stanfield
Markus Schmied
U.S. Geological Survey
Paul Zahl
Psammophile, courtesy Wikimedia

Illustrators

Sean McNaughton
Raul D. Martin

Producer

Caryl-Sue, National Geographic Society

Last Updated

July 19, 2012

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