Radial growth rates of microatolls on a reef flat on Abaiang, Republic of Kiribati

Disk-shaped coral colonies called microatolls have live coral tissue on their outer edges and nonliving centers. The upward growth of these structures is limited by the level of lower low water and the yearly outward growth in at least one species, Porites lutea, is recorded in the upper surface of the disks in the form of annuli. From March 1998 until August 2005, we used two different methods to assess radial growth rates of Porites lutea microatolls on the ocean reef fl at of Abaiang Atoll, Republic of Kiribati . We found that annual growth rates varied substantially during the 7.9 years of observation, from 0.7 to 2.6 cm/yr, with a mean of 1.6 cm/yr.