What threats do coral reef and other ocean communities face?
Interactive Study Guide
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Guiding Question 13.4
What threats do coral reefs and other ocean communities face?
Why You Should Care
Coral reefs are found in shallow coastal areas in warm tropical and subtropical waters (between 30° N and 30° S) worldwide. Coral grows in areas with enough light (shallower than 80 feet) and close enough to estuaries to use nutrients washing out of rivers. Outside of these waters, the waters are too cold or too deep for the coral to establish and grow.
Coral reefs are unique marine ecosystems, but every place in the ocean faces similar threats. Humans overfish with techniques that take too much, destroy bottom habitat, or selectively harvest fish for the pet industry. Coral reefs are more productive, more diverse, and closer to shore and so suffer greater damage from these activities.
1.
When ocean temperatures increase, what happens to coral polyps?
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2.
Which of these factors cannot cause coral bleaching?
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3.
What is the relationship between ocean acidification and coral bleaching?
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The relationship is indirect: As higher levels of atmospheric carbon dioxide warm the atmosphere and ocean, they also decrease the ocean’s pH. But the acidification does not cause coral bleaching—the increasing ocean temperatures do that. Acidification might dissolve coral skeletons faster, but it won’t cause them to lose their zooks.
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Why are most of the reefs that are endangered in tropical and sub-tropical oceans?
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5.
Which region has lost the most coral reefs?
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6.
What is the greatest threat to coral reefs today?
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7.
How do our fishing techniques deplete ocean communities?
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8.
Which of the following is a type of pollution in ocean communities?
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9.
How can nutrient pollution be a problem at high levels and necessary for coral reefs at lower levels?
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It is a question of degrees. At lower levels, it is necessary for the producers to survive. There is some breakdown by decomposers, too. At higher levels, so much oxygen is required to break down the extra nutrients that decomposers take over and create hypoxic (low-oxygen) “dead zones.” In these areas, there is so little oxygen that fish cannot survive, so we call that area polluted (see Chapter 16).
