An open atoll in the Northwest Hawaiian Islands (NWHI) that consists of a large, crescent-shaped reef surrounding numerous small, sandy islets. While the land area is only one-fourth square kilometer (67 acres), the total coral reef area of the shoals is over 938 square kilometers (232,000 acres). The reef system associated with French Frigate Shoals supports the greatest variety of coral species in the NWHI, with 41species of stony corals documented. It also supports more than 600 species of invertebrates, many of which are endemic to the area, over 150 species of algae, and many species of fishes. Hundreds of green sea turtles travel to the shoals for safe nesting. The many small islets of French Frigate Shoals also provide refuge to the largest sub-population of endangered Hawaiian monk seals.