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WHAT IS A COCCOLITHOPHORE?
Like any other type of phytoplankton,
coccolithophores are one-celled marine
plants that live in large numbers throughout the upper layers of the ocean.
Unlike any other plant in the ocean, coccolithophores surround themselves with a
microscopic plating made of limestone (calcite). These scales, known as
coccoliths, are shaped like hubcaps and are only three one-thousandths of a
millimeter in diameter.
 What coccoliths lack in size they make up in volume.
At any one time a single coccolithophore is attached to or surrounded by at
least 30 scales. Additional coccoliths are dumped into the water when the
coccolithophores multiply asexually, die or simply make too many scales. In
areas with trillions of coccolithophores, the waters will turn an opaque
turquoise from the dense cloud of coccoliths. Scientists estimate that the
organisms dump more than 1.5 million tons (1.4 billion kilograms) of calcite a
year, making them the leading calcite producers in the ocean.
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WHAT DO THEY DO TO THE ENVIRONMENT? |
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Coccolithophores are
not normally harmful to other marine life in the ocean.
The nutrient-poor conditions that allow the coccolithophores to exist will
often kill off much of the larger phytoplankton. Many of the smaller fish and
zooplankton that eat normal phytoplankton also feast on the coccolithophores.
In nutrient-poor areas where other phytoplankton are scarce, the
coccolithophores are a welcome source of nutrition.
In the long term, the
plants seem to be good for the environment. Coccolithophores make their
coccoliths out of one part carbon, one part calcium and three parts oxygen
(CaCO3). So each time a molecule of coccolith is made, one less carbon atom is
allowed to roam freely in the world to form greenhouse gases and contribute to
global warming. Three hundred twenty pounds of carbon go into every ton of
coccoliths produced. All of this material sinks harmlessly to the bottom of the
ocean to form sediment.
The coccolithophores' short-term effect on the
environment is somewhat more complex. This effect again has to do with the
formation of their coccoliths and the chemical reaction involved in the process.
The chemical reaction that makes the coccolith also generates a carbon dioxide
molecule, a potent greenhouse gas, from the oxygen and carbon already in the
ocean. While much of the gas is sucked back in by the coccoliths (all plants
take in carbon dioxide for food) some of it escapes into the atmosphere and
immediately becomes part of the greenhouse gas problem. Scientists are
concerned in the short term that greenhouse gases will cause the upper layers of
the ocean to become more temperate and stagnant. This would increase the number
of coccoliths in the world, which would produce more greenhouse gas.
The
coccolithophores also affect the global climate in the short term by increasing
the oceans' albedo. Albedo is the fraction of sunlight an object
reflects--higher albedo values indicate more reflected light. Coccolithophore
blooms reflect nearly all the visible light that hits them. Since most of this
light is being reflected, less of it is being absorbed by the ocean and stored
as heat.
Retrieved from http://earthobservatory.nasa.gov |
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