Coral recruitment in Moorea, French Polynesia:the importance of patch type and temporal variation

Abstract

Coral recruitment to artifi ial substrata (ceramic tiles) was measured in shallow back-reef (1–2 m depth) and deeper fore-reef (8–10 m depth) habitats on the island of Moorea, French Polynesia. Recruitment to three patch types within each of those habitats was measured at 4 month intervals for 3 years. Recruitment rates did not differ between fore-reef and back-reef habitats nor between sites within a habitat when data for the 3 years of the study were combined. There was a strong effect of patch type within the back-reef habitat on patterns of coral recruitment. In the shallow back-reef habitat, recruitment was 2–6 times higher to tiles inside territories of the damselfish, Stegastes nigricans (Lacepede), than to tiles in patches characterized by heavy grazing (crustosealgal dominated) or high cover of fleshy algae (especially Turbinaria ornata (Turner) J. Agardh). This pattern was not seen on the fore-reef where other species of damselfish were present. Temporal patterns of coral recruitment in Moorea were characterized by large inter-annual variability, as well as seasonal variability. Mean recruitment rates ranged between < 1 and 16 recruits/tile (tile surface area was 486 cm 2) over the course of the study. A total of 2801 recruits were found on 939 tiles in 3 years. Highest recruitment rates occurred in the December to April period, which corresponds to the period of warmest water temperatures. Recruits in the family Pocilloporidae were found year-round, with a seasonal peak in the December to April period, and accounted for 63% of total recruitment over 3 years. Recruitment of acroporids followed the same pattern, but contributed only 5% to total recruitment. Poritids were also found year-round, but in highest relative proportion in the August–December period; recruitment of poritids accounted for 26% of the total over 3 years. Recruitment was highest in the first year of the study, with a large increase in recruitment immediately preceding a major coral bleaching event.