Multiple Choice, Multiple Answers

Read the passage and select ALL statements it supports.

Coral reefs cover less than one percent of the ocean floor, yet they shelter roughly a quarter of all marine species. These reefs are built by tiny animals called polyps, which deposit calcium carbonate to form hard skeletons over thousands of years. Reefs protect coastlines by absorbing the force of incoming waves, and they support fishing and tourism industries worth billions of dollars. Unfortunately, rising sea temperatures can cause coral bleaching, in which stressed polyps expel the colourful algae living in their tissues. Without these algae, the coral loses its main source of food and may eventually die if warm conditions persist for too long.