Natural settlement dynamics of a young population of Turbinaria ornata and phenological comparisons with older populations

Our study was done during 16 months on two sites at Moruroa to (i) compare Moruroan populations (young) with Tahitian populations (old) of Turbinaria ornata and (ii) follow the natural dynamic of a young population at Moruroa. Moruroan and Tahitian populations have maximal density and maximal reproductive characteristics during the cool and hot seasons, respectively. Recruits are present throughout the year at all sites. Within the reference field site, individuals were initially distributed regularly and then became clumped through time, recruits appeared around adults. Recruits mortality followed a similar pattern, whereas mortality of adults and juveniles was even throughout the monitoring period. Populations initially had similar proportions of recruits, juveniles and adults (28, 40 and 32%, respectively), but at the end, recruits represent 92% of the population. A linear relationship between the number of individuals present within the station and the colonized substrate area was determined (R2 = 0.96), suggesting a limiting effect of the substrate against the settlement of T. ornata with time. Moreover, the growth of recruits in the close vicinity of adults was arrested in the young populations: recruitment may therefore, significantly buffer high rates of adult mortality. It may contribute to the invasion and, more interesting to the persistence of T. ornata in new colonized area.