Coral reefs are limestone(石灰岩)formations produced by a sedentary(定着性の)marine animal, related to the sea anemone(イソギンチャク), called the stony coral, which secretes(分泌する)an exoskeleton(外骨格)of calcium carbonate(炭酸カルシウム), often in large colonies and over generations. As these massive calcareous(石灰質の)formations are produced, break, and pile on top of one another, they become home to a large variety of plant and animal life.