Cactus coral

Biology

The cactus coral is a hard coral with a limestone skeleton that may grow as an isolated colony or may form large colonies that can cover over 10 metres. Its polyps extend their tentacles at night to catch plankton, but it also takes in nutrients from photosynthesis carried out by small algae, called zooxathellae, that live within its tissues. The algae benefit in turn from the protection of the coral.

Conservation

Coral reefs around the world are in danger. The major threat to corals is global climate change, high temperatures and ocean acidification. Localized threats to corals include fisheries, invasive species, dynamite fishing, chemical fishing, pollution, sedimentation, and human recreation and tourism activities.