Vocabulary

algal bloom chemotaxis alginate carrageenan agar diatomaceous earth malaria sporozoite merozoite gametocyte giardiasis cryptosporidiosis trichomoniasis

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www.scilinks.org Topic: Protists Keyword: HM61245

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Ecology of Protists

Temperature and the availability of light and nutrients influence the growth of algal populations. Algae grow in the photic zone, the portion of a body of water through which light penetrates. Nitrate and phosphate availability usually limits algal growth rates. In the open ocean, the availability of iron ions may limit algal growth.

High water temperatures and nutrient concentrations can cause algal blooms, a vast increase in the concentration of diatoms and other photosynthetic protists. Algal blooms often occur during spring in bays and estuaries and frequently harm these environments. During an algal bloom, large numbers of dying protists sink to the bottom, where they decompose. Bacterial decomposers use up oxygen, which fish, crustaceans, and other sea life need to survive. Dropping oxygen levels can cause these larger species to die off.

Dinoflagellate blooms cause red tides, shown in Figure 25-17. Toxins produced by dinoflagellate blooms concentrate as they move up the food chain. These toxins can sicken or kill humans and other organisms that consume clams, oysters, or krill that have fed on the red tide dinoflagellates.

figure 25-17

Because red tides produce dangerous toxins, people in some areas are often advised not to eat shellfish during the summer months, the time when red tides are most likely to happen.

figure 25-17

Because red tides produce dangerous toxins, people in some areas are often advised not to eat shellfish during the summer months, the time when red tides are most likely to happen.

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