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The French anthropologist Claude Lévi-Strauss wrote, "The scientific mind does not so much provide the right answers as ask the right questions" (Patterson, 2003). This truism has become apparent to me through my years of performing scientific research for school science projects. Each year my projects became more sophisticated, and my love of science developed into an admiration of both the natural world and technology. I even found myself intrigued by one of the greatest naturalists and his theories. Charles Darwin and his evolutionary theory struck a chord with me. Since studying his work, I have not only developed an interest in laboratory research, but I have learned the importance of field research as well. This interest in both laboratory and field research resulted in a two-year study expedition focusing on diatoms and their possible role as indicators of water quality. I became interested in diatoms when my science teacher told me about some of the studies he had done as a part of a graduate fellowship. I was immediately interested in these amazing microscopic organisms. In order to formulate the "right questions," my research objective was to learn as much as possible about diatoms and their environment. This would provide the foundation for a well-designed scientific investigation or research quest. My research involved reading scientific journals and books, visiting local university libraries and the California Academy of Sciences in San Francisco, and seeking advice from leading diatomists such as Sarah Spaulding. I also contacted Heal the Bay, an environmental organization that monitors water quality in southern California, and after participating in their training program, I developed a basic understanding of environmental issues and also became certified in water chemistry.
Background Research Diatoms inhabit most aquatic habitats, such as lakes, wetlands, oceans, and estuaries (Stoermer and Smol, 1999). Like most plants, diatoms need sunlight for energy, in addition to nutrients such as nitrates and phosphates and carbon dioxide (Sobehrad, 1997). They are members of the largest group of algae, the golden algae phylum. Their cell walls fit together much like a lid fits on a box (Vinyard, 1979). These walls, primarily made up of silica, are called frustules. |
There are more than 12,000 species of diatoms. They live in fresh ponds, streams, rivers, or on the surface of the ocean, where they are a component of phytoplankton (Sobehrad, 1997). Though some diatoms are free-floating, some are not. Many cling to or hook onto surfaces underwater, such as aquatic plants, mollusks, crustaceans, turtles, rocks, and other surfaces (Waggoner, 2001). I spoke to Sarah Spaulding, an expert on diatoms at the California Academy of Sciences, and learned that diatoms that grow on rocks are called epilithic diatoms (Spaulding, pers. com., 2001).  Robyn collecting materials from Limekiln Creek. Diatoms are important in aquatic ecosystems because they are part of different food webs and they oxygenate the water (Stoermer and Smol, 1999). Diatoms contribute to organic carbon fixation by photosynthesis (Waggoner, 2001). The many different species of diatoms add to the biodiversity and genetic resources in bodies of fresh and salt water. Diatoms can be classified differently depending on the classification system used. They make up either Bacillariophyceae in the phylum Chrysophyta, or they make up the phylum Bacillariophyta in the kingdom Protista (Encarta, 1999). There are two main types of diatoms. Pennate diatoms are usually found in shallow freshwater areas and are elongated and cigar- or pen-like in shape. Centric diatoms, the second type, are circular, triangular, or irregularly shaped, and they are primarily found in the ocean (Prescott, 1964). Synedra ulna, the diatom that my studies focused on, is an epilithic and pennate diatom. As an example of a diatom that grows best in the presence of nitrates, it can be an indicator of this water characteristic. Synedra are described as having narrow frustules, free-floating or sometimes in colonies (Smith, 1950). They also can be benthic, meaning they grow on different surfaces. The valves are linear and on some, slightly curved. Synedras live in a variety of habitats, enabling researchers to study them in various aquatic environments (Smith, 1950). As a species within the algal community, Synedras have specific ecological requirements and tolerances (Freedman, 1996). Nitrates, phosphates, and hydrogen ions are three of the major chemicals present in water, and all three have effects on the health of aquatic organisms. Nitrate is the most oxidized form of nitrogen found in the natural world. It is one of the most water-soluble anions known (Campbell et al., 2001). Plants need nitrogen as a nutrient, and most plants prefer nitrate to ammonia (Campbell et al., 2001). Diatoms are forms of algae, so they also need a supply of nitrate. |
 
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