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Coral reefs harbor one of the highest biodiversity on Earth but increasing disturbances have often led to rapid shifts from coral to algal states, prompting the development of conservation methods, including coral restoration. While most studies have focused on the medium and long-term effects of restoration on fish assemblages, less is known about its short-term effects (i.e., within one month) on associated communities. This study explored the short-term impacts (<1 month) of coral restoration, including four restoration conditions, on fish abundance, diversity, and assemblages in a marine educational area (a small coastal area managed by a scholl in the frame of an eco-citizen pedagogical program) in Bora Bora, French Polynesia. Sixteen dead reef patches previously covered by macroalgae were grouped into four conditions as follows: four were non-restored (control condition), four were restored to 25% living coral cover (condition 25%), four to 50% living coral cover (condition 50%), and four were restored to 75% living coral cover (condition 75%). The abundance of fish at adult and juvenile stages was assessed, before and after coral restoration, using the fixed-point method for a period of 5 min on each of the 16 reef patches. Two successive observation periods were conducted for each patch: one focusing on more visible and mobile fish, and another on more cryptic species. Surveys were conducted one day and three days prior to restoration, and then 24 days and 28 days post-restoration. For adults, the difference in abundance, number of species, and diversity before and after restoration were not significant between the conditions. Similarly, for juveniles, no significant differences were observed when considering the conditions and restoration. Before restoration, the fish assemblages were randomly distributed between the four conditions for both adults and juveniles. After the restoration, the inter-conditions similarity decreased significantly for adults, but not for juveniles. Some species were associated with the more restored patches (Chaetodon citrinellus , Halichoeres trimaculatus , and Zanclus cornutus). Finaly, the restoration seemed to have variable effects depending on the trophic groups. Coral restoration has short-term effects on fish assemblages, indicating the effectiveness of restoration efforts even within a brief period. These rapid changes underscore the remarkable ability of adult fish to adapt to rapidly changing environments. • Short-term impacts (<1 month) of coral restoration on fish abundance, diversity, and assemblages in a marine educational area in Bora were studied. • Some species were associated with the more restored patches (Chaetodon citrinellus , Halichoeres trimaculatus , and Zanclus cornutus). • There was no short-term effect on abundance and diversity but there was a significant modification of adult assemblages. • It indicates the effectiveness of restoration efforts even within a brief period. • These rapid changes underscore the remarkable ability of adult fish to adapt to rapidly changing environments. [ABSTRACT FROM AUTHOR]

The universally known subsidence theory of Darwin, based on Bora Bora as a model, was developed without information from the subsurface. To evaluate the influence of environmental factors on reef development, two traverses with three cores, each on the barrier and the fringing reefs of Bora Bora, were drilled and 34 uranium-series dates obtained and subsequently analysed. Sea-level rise and, to a lesser degree, subsidence were crucial for Holocene reef development in that they have created accommodation space and controlled reef architecture. Antecedent topography played a role as well, because the Holocene barrier reef is located on a Pleistocene barrier reef forming a topographic high. The pedestal of the fringing reef was Pleistocene soil and basalt. Barrier and fringing reefs developed contemporaneously during the Holocene. The occurrence of five coralgal assemblages indicates an upcore increase in wave energy. Age-depth plots suggest that barrier and fringing reefs have prograded during the Holocene. The Holocene fringing reef is up to 20 m thick and comprises coralgal and microbial reef sections and abundant unconsolidated sediment. Fringing reef growth started 8780 ± 50 yr bp; accretion rates average 5·65 m kyr−1. The barrier reef consists of >30 m thick Holocene coralgal and microbial successions. Holocene barrier-reef growth began 10 030 ± 50 yr bp and accretion rates average 6·15 m kyr−1. The underlying Pleistocene reef formed 116 900 ± 1100 yr bp, i.e. during marine isotope stage 5e. Based on Pleistocene age, depth and coralgal palaeobathymetry, the subsidence rate of Bora Bora was estimated to be 0·05 to 0·14 m kyr−1. In addition to subsidence, reef development on shorter timescales like in the late Pleistocene and Holocene has been driven by glacioeustatic sea-level changes causing alternations of periods of flooding and subaerial exposure. Comparisons with other oceanic barrier-reef systems in Tahiti and Mayotte exhibit more differences than similarities. [ABSTRACT FROM AUTHOR]