Definition (Encyclopedia of Global Warming)
Plankton (from the Greek planktos, or wanderer) comprise a vast assortment of life-forms with limited or no swimming power that largely drift in the ocean. They are divided into the plantlike phytoplankton and the animal-like zooplankton.
Phytoplankton comprise at least four thousand species of plants that, as on land, use sunlight in the process of photosynthesis to generate sugars and other high-energy organic compounds. They live in the ocean’s euphotic zone, the sunlit upper layer, which is only tens of meters deep. Phytoplankton range in size from microscopic to a millimeter in length and include single-celled organisms and tiny clumps of algae.
Because the ocean covers 71 percent of the Earth’s surface, phytoplankton are a major driver of Earth’s carbon cycle. Their photosynthesis extracts carbon dioxide (CO2) from surrounding water and replaces it with oxygen. The resulting changes in oceanic gas levels change atmospheric gas levels as well. Some phytoplankton (such as coccolithophores) accretecalcium carbonate (CaCO3) for shielding. If the carbon contained in their bodies reaches the ocean depths, it may be sequestered there for years, or even for millions of years.
Oceanic nutrient levels are major determinants of phytoplankton productivity. The most fertile areas are river estuaries, shallow waters, and upwelling areas in the deep ocean. Phytoplankton are eaten by zooplankton. Zooplankton...
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Significance for Climate Change (Encyclopedia of Global Warming)
In 1988, oceanographer John Martin declared, “Give me half a tanker of iron, and I can start a new ice age.” Martin was referring to phytoplankton growth in the “bluewater desert” areas of the deep ocean. The creatures’ growth rate is often limited by the availability of trace amounts of iron. It has been hypothesized that ice ages may result from large amounts of wind-blown dust enriching the oceans with iron. Such enrichment could have caused phytoplankton blooms that reduced atmospheric CO2 levels, thus reducing the greenhouse effect and cooling the planet.
Similarly, Martin suggested that artificial iron fertilization in the oceans might reduce global warming. (A major campaign of oceanic fertilization would be a species of geoengineering.) Several limited experiments of a few hundred square kilometers and a few days duration have confirmed major iron fertilization in the Pacific Ocean and in the southern ocean around Antarctica.
Phytoplankton emit the sulfur-bearing gases dimethyl sulfide (DMS, CH3SCH3) and carbonyl sulfide (COS). Their breakdown product, sulfur dioxide (SO2), produces airborne particles (aerosols) that reflect visible light but allow infrared light (heat waves) to pass through, thus causing more cooling. Ocean fertilization could be self-funding, because a part of the increased planktonic production could be harvested via increased fisheries production.
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Further Reading (Encyclopedia of Global Warming)
Adhiya, Jagat, and Sallie W. Chisholm. “Is Ocean Fertilization a Good Carbon Sequestration Option?” Cambridge, Mass.: MIT Press, 2001. This white paper presents the case against oceanic fertilization.
Field, Christopher B., and Michael R. Rapauch, eds. The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World. Washington, D.C.: Island Press, 2004. This compendium of articles from the Scientific Committee on Problems of the Environment (SCOPE) discusses the major atmospheric sources and sinks. The final chapter details possible advantages and limitations of ocean fertilization.
Mitra, Abhijit, Kakoli Bannerjee, and Avijit Gangopadhyay. Introduction to Marine Plankton. Delhi, India: Daya, 2008. Although the authors emphasize plankton in the waters near India, they provide an excellent overall description of plankton, its role in the carbon cycle, fertilization effects, identification, and even culturing. However, the book does not comment directly on oceanic fertilization or acidification.
“The Ocean in a High-CO2 World.” Special Section in Journal of Geophysical Research 110, no. C9 (2005). Includes papers on the carbon cycle, as well as articles making arguments for and against oceanic fertilization.
Royal Society. Ocean Acidification Due to Increasing Atmospheric Carbon Dioxide. London: Author, 2005. The Royal Society in the United Kingdom...
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Plankton (Encyclopedia of Science)
Plankton are microscopic plants and small animals that live in the surface waters of oceans, lakes, and rivers and drift with the currents. They include bacteria, fungi, algae, protozoa, invertebrates, and some vertebrates.
Phytoplankton are photosynthetic, meaning that they use sunlight to convert carbon dioxide and water into organic molecules such as glucose to use as food. Phytoplankton include microscopic algae, blue-green bacteria, and some true bacteria. These organisms exist in waters where light is able to penetrate. Phytoplankton form the base of nearly all aquatic food chains, directly or indirectly supplying the energy needed by most aquatic protozoa and animals.
(The entire section is 488 words.)