coral reefs

Bustling with a spectacular diversity of life, coral reefs are the rain forests of the oceans. Coral reefs are built by thousands of tiny organisms called polyps (PAH-lips), which form the outside layer of the reef. The inside layers of a reef are made of the skeletons of dead coral, some of which lived millions of years ago. Coral reefs provide shelter and food for thousands of different kinds of living organisms.

Made by: reef-builder corals
Habitat: clear, warm, shallow, tropical waters
Threats: human contact, pollution, blast fishing, runoff, global warming
Types: fringing reefs extending from the coastline into the sea; barrier reefs, which form offshore; and atolls, circular reefs around an island
Significance: home to about a million marine species and protect our shorelines
Status: extremely endangered

Image credits: main image, courtesy of NOAA, Florida Keys National Marine Sanctuary.