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Patterns and processes affecting juvenile scleractinian corals have received very little attention due to difficulties associated with detecting small corals on natural substrata. However, processes occurring during juvenile life stages are likely to play a strong role in population ecology. In particular, spatial differences in juvenile demographic rates may result in prominent differences in population and community structure for corals. In the present study, we compared the density, taxonomic composition, size structure, growth and mortality rates of juvenile corals (≤50 mm) and the cover and composition of adult coral assemblages among sites on Trunk Reef (central Great Barrier Reef) and Moorea (French Polynesia). There was significant regional variation in the taxonomic composition of coral assemblages within both adult and juvenile assemblages, with Pocillopora being the predominant coral genus in Moorea and Acropora at Trunk Reef. However, there were no differences in the density, growth or mortality rates of juvenile corals between Moorea and Trunk Reef. Most of the variation in these variables was evident at the small (within-reef) scale, with exposed sites having lower densities and higher rates of mortality of juvenile corals than sheltered sites at both locations. The lack of geographic variation in the density, growth and mortality rates of juvenile corals is interesting given that the cover of adult coral was 3-fold higher on Moorea (31.1%) than Trunk Reef (10.8%), suggesting that adult coral assemblages are structured more by differential adult mortality, larval settlement or very early post-settlement mortality (before colonies can be observed in situ), rather than demographic rates of juvenile growth or mortality.

In this study, we describe spatio-temporal variation in coral recruitment in the back reef of Moorea, French Polynesia, and explore the extent to which it is associated with community struc- ture, seawater temperature, and wave regimes. Recruitment was assessed with settlement tiles deployed at 10 sites on the north, southeast, and southwest shores and sampled every 5 to 7 mo from 2005 to 2007. Temperature and waves were measured using thermistors and pressure sensors, and community structure was assessed using in situ surveys. Mean recruitment varied from 0 to 6 recruits tile -1 (510 cm 2 ) and was generally greater in the second compared to the first year of the study. Recruitment varied among sites, and this variation was similar between years but differed among sampling periods: acroporids were common on the southwest shore between January and September, but rare from September to January; poritids were common on the north shore between September and January, but rare on the southwest shore from January to September; and pocillo- porids were found all year, but at slightly elevated densities between January and September. The mean daily seawater temperature, and the daily range, varied among sites, but neither was closely related to coral recruitment, and both were of biologically small magnitudes. The coral community structure also varied among sites, but likewise, was not associated with coral recruitment. In contrast, outer reef wave energy exposure, which likely played an important role in driving cross-reef trans- port of seawater into the lagoon, differed between shores and seasons in a pattern consistent with the variation in coral recruitment in the back reef. We hypothesize that coral recruitment in the back reef of Moorea is influenced by the interaction of seasonal variation in wave exposure, family-level differ- ences in coral reproductive timing, and the spatial distribution of adult corals.

We analysed the interannual variability of the major reef communities (algae, corals and fishes) on the outer slope of the Tiahura sector on Moorea Island between 1991 and 1997, and exam- ined the impacts of natural disturbances on these communities. Patterns of temporal variation and the response to natural perturbations were clearly different among the taxa examined. A sharp decrease in the percent cover of branching corals (Pocillopora and Acropora) followed cyclonic and bleaching events that occurred in 1991. After 1993, a slight increase in coral cover values was recorded, and can be interpreted as a sign of recovery. Despite a similar proportion of bleached colonies at the begin- ning of bleaching events in 1991 and 1994, the bleaching in 1994 had no significant impact on coral cover. This result demonstrates the importance of understanding the ecological history of reefs (i.e. the chronology of disturbances) in interpreting the specific impacts of a particular disturbance. The decline in coral cover was accompanied by an increase in the percent cover of turf algae, but sur- prisingly, the percent cover of macroalgae did not show any significant temporal variation during the 7 yr period. Thus, the decrease in the percent cover of corals, which opens up new substrate, does not always result in an increase in macroalgal cover. The temporal variation of the fish community was mainly characterized by (1) the high variability in the recruitment of juveniles, with a peak in 1991; (2) the slight increase in the density of adult species; and (3) the decrease in the density of coralli- vorous chaetodontid fishes from 1991 to 1994. Since corals were the only taxon directly affected by natural disturbances, they were consequently the cause of the indirect effects of these disturbances (i.e. increase in turf algae and decrease in chaetodontid fishes), and can therefore be regarded as the 'key component' of the outer slope reef communities in Moorea.

Nine atolls were characterized in order to understand how physical factors control the species composition, diversity, and abundance of macrobenthic (coral, mollusc, echinoderm, and algal) communities inside the lagoons. Only one region, the central part of Tuamotu Archipelago, French Polynesia, was considered, in order to minimise the variation due to regional factors between regions. The lagoons investigated showed a gradient of physical factors, providing various landscape configurations. The physical factors were surface area, abundance of pinnacles, degree of hydrodynamic aperture, and relative importance of passes in this degree of aperture. Macrobenthic communities were characterized by low diversity and strong dominance of a few mollusc or echinoderm species that generally occurred in lagoons without passes. Correlation analyses indicated that species richness increases with the surface area of the lagoon. Species richness of corals, echinoderms, and macroalgae was also higher in lagoons having numerous pinnacles. Canonical correspondence analyses revealed that the distribution and the relative abundance of coral, echinoderm, and macroalgae species were correlated to the relative importance of passes, whereas degree of aperture of the lagoon was also relevant for corals and molluscs. The physical factors that control the processes of water exchange between ocean and lagoon, including passes, submerged reef flats, and spillways, influence the identity and the abundance of most macrobenthic species inside the lagoons.