Answer to Critical Thinking Activity - Chapter 33

1. Reef-building, scleractinian corals in particular owe their success to the fact that most have symbiotic dinoflagellate algae in the genus Symbiodinium living inside their tissues. Coral polyps also use their tentacles and nematocysts to feed, but Symbiodinium may actually produce most of a coral's food. For this reason, reef-building corals are exclusively shallow-water dwellers; without light they cannot survive.

2. The relatively pristine reefs of Papua New Guinea are coming under increasing threats from logging, poor land management and sewage. Black coral, giant clams and shells are poached by Japanese and Taiwanese fishing boats. Turtles are over-harvested and explosives are used for fishing.

3. Existing coral reefs have been formed since the last of three glacial periods in the Pleistocene epoch, 10,000 years ago. Seawater trapped as ice in enormous glaciers caused sea level to fall. Consequently, all previously formed coral reefs probably died of exposure. When the glaciers melted, sea level rose to its current position and present-day reefs began to develop.

4. All marine food webs or chains begin at or near the surface where there is light. As organisms die on or near the edges of a reef, their bodies float downward into the deep sea where they are scavenged by deep water fish and other organisms. If the reef above dies, most of the food supply for those animals thousands of feet below is cut off.

5. Cyanide interferes with cellular respiration and is one of the most toxic and fast acting poisons known. Reef fishermen in the South Pacific and Southeast Asia are presently using cyanide to stun fish to catch for sale to live fish meat markets, and to aquarium enthusiasts. As if catching fish in this manner weren=t bad enough, using cyanide is especially horrible because it kills EVERYTHING, plant and animal, thus destroying the habitat. This is an immoral and criminal act, and it must be stopped.

   You can help stop this practice. Support legislation prohibiting the importation of fish that have been caught using cyanide. If you own a tropical aquarium, demand that your aquarium store only purchase fish that have been certified cyanide-free. Do not purchase fish from a live fish restaurant unless you are certain that it has been caught without the use of cyanide.