The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
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Phytoplankton are microscopic, photosynthetic organisms that float in the water of the oceans and bodies of freshwater (the word phytoplankton is derived from the Greek for "drifting plants"). The most abundant organisms occurring within the phytoplankton are algae and blue-green bacteria, but this group also includes certain kinds of protists (especially protozoans) that contain symbiotic algae or bacteria.
Phytoplankton are responsible for virtually all of the primary production occurring in the oceans. Marine phytoplankton range in size from extremely small blue-green bacteria, to larger (but still microscopic) unicellular and colonial algae. Oceanic phytoplankton are grazed by tiny animals known as zooplankton (most of which are crustaceans). These are eaten in turn by larger zooplankton and small fish, which are fed upon by larger fish and baleen whales. Large predators such as bluefin tuna, sharks, squid, and toothed whales are at the top of the marine food web. Marine phytoplankton are much more productive near the shores of continents, and particularly in zones where there are persistent upwellings of deeper water. These areas have a much better nutrient supply, and this stimulates a much greater productivity of phytoplankton than occurs in the open ocean. In turn, these relatively fertile regions support a higher productivity of animals. This is why the world's most important marine fisheries are supported by the continental shelves (such as the Grand Banks and other shallow waters of northeastern North America, near-shore waters of western North and South America, and the Gulf of Mexico) and regions with persistent upwellings (such as those off the coast of Peru and elsewhere off western South America, and extensive regions of the Antarctic Ocean).
Some inland waterbodies occur in inherently fertile watersheds, and are naturally eutrophic, meaning they have a high productivity and biomass of phytoplankton (in shallow waters, larger aquatic plants may also be highly productive). So-called "cultural eutrophication" is a kind of pollution caused by nutrient inputs associated with human activities, such as the dumping of sewage waste and the runoff of fertilizer from agricultural land. Both fresh and marine waters can become eutrophic through increases in their nutrient supply, although the problem is more usually severe in freshwaters. The most conspicuous symptom of eutrophication is a large increase in the biomass of phytoplankton, which in extreme cases is known as an algal "bloom."