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| Read each sentence and identify the word/phrase that you believe correctly completes the statement. Then, click on the arrow to see if your answer is correct. 1. Modification or destruction of habitats in rich but fragile communities like , , and is a serious threat to the marine environment. 2. Pollution may be defined as a decrease in caused by the addition of substances or materials by humans. 3. Pollution by sewage is a major problem along the coast. Raw sewage is particularly hazardous because it . Partial treatment usually results in large amounts of that overcome bottom communities and overfertilize the water. Overfertilization of the water is known as . 4. Oil is a common marine pollutant with widespread effects. Of all marine communities, those found in and water are the most affected. 5. is the phenomenon shown by chlorinated hydrocarbons and other synthetic chemicals when they accumulate in the food chain. It is a consequence of the fact that these chemicals are ; that is, they cannot be broken down by organisms. 6. Other marine pollutants prominent for their toxicity are PCBs and heavy metals like , , , and . 7. The pumping of heated water from power plants and other operations into the ocean is known as . 8. Species become when they disappear forever. We say they become , however, when their disappearance is brought about by humans. Species like the blue whale that are in immediate danger of disappearing are known as . 9. introduced on purpose or by accident may be very harmful because they can eliminate , that is, those species characteristic of a particular location. 10. Efforts to enhance the marine environment include by transplanting individuals of depleted species and building artificial to improve fishing. |