The entire west coast of the South American continent cannot support very much coral growth. This is due to the Peru Current that brings cold water from the southern oceans around Antarctica along the coast of Peru.
... are a highly developed grazer of the reef. With strong calcified, fused teeth that scrape off coralline algae and the calcareous surface that most algae live on. They are one of the major sources for the fine calcareous silt found around a reef.
