Reef Corals of Fanning Island

Abstract

Recent surveys indicate that the diversity of reef corals at Fanning Island is greater than previously estimated. Most of the approximately 70 species belonging to 32 genera and subgenera typically are found in one of three environments. A turbid lagoon fauna has high abundance but lower diversity of predominantly branching forms. The clear lagoon coral fauna has both high abundance and diversity of predominantly massive and encrusting corals. The greatest number of species and forms of corals are found on the leeward ocean reefs. The abundance and diversity of corals along windward reef slopes are controlled by wave action. Although Fanning and others of the Line Islands presently contain the greatest generic diversity of corals of any island group in the central and eastern Pacific, diversity is considerably less than that reported for island groups in the western Pacific. Geographic isolation appears to be the most plausible factor accounting for reduced coral diversity in the Line Islands. The reef coral fauna is more nearly comparable with that of island groups south and west than to those of the north (Hawaii).