Restoring the reef: Coral restoration yields rapid impacts on certain fish assemblages

International audienceCoral 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, 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

Roadside sales activities in a South Pacific Island (Bora-Bora) reveal sustainable strategies for local food supply during a pandemic

During the COVID-19 pandemic, the reduced exports and imports as well as the lack of activity due to the interruption in the international tourism economy seriously impacted food security in many Pacific Islands. People often returned to natural resources to provide for themselves, their families, or to generate income. On Bora-Bora Island, the major tourist destination in French Polynesia, roadside sales are widespread. Our study analyses the impact of the COVID-19 pandemic on roadside sales activities through a census of roadside stalls on the five Bora-Bora districts conducted before (January and February 2020), during (from March 2020 to October 2021) and after (from November to December 2021) health-related activity and travel restrictions. Our results showed that the marketing system for local products (fruits, vegetables, cooked meals, and fish) increased in the form of roadside sales during the COVID-19 in two of the five districts of Bora-Bora. Roadside selling would be an alternative system for providing food to the population at Bora-Bora during a global crisis and that could reveal itself sustainable after this pandemic

Herbivory effects of sea urchin species on a coral reef (Bora-Bora, French Polynesia)

WOS:000958865300001Macroalgae are becoming dominant on coral reefs worldwide, replacing corals as key habitat formers. Incrementing consumption rates by herbivores, such as sea urchins, has been identified as a viable strategy for promoting coral recovery. By means of a 28-day experiment, we assessed the grazing effects of the sea urchins, Tripneustes gratilla and Diadema setosum, on the macroalgal assemblages of shallow reefs at Bora-Bora (French Polynesia). In particular, each urchin species was either absent or maintained, using cages (n = 10), at a density of 5 individuals/m2. T. gratilla exerted stronger negative effects than D. setosum on all the examined macroalgae (i.e., Turbinaria ornata, Padina boryana, Halimeda spp, Dictyota spp). In addition, the grazing effects by T. gratilla on macroalgae emerged shortly after the start of the experiment, more rapidly than those of D. setosum. Despite an apparent lower food preference for T. ornata in D.setosum, all macroalgae were consumed by both species and the composition of the macroalgal assemblages (i.e., the proportion of each species) did not change after 28 days. Overall, our study suggests that herbivorous sea urchins, when at relatively high densities, could contribute to sustaining coral-dominance on coral reefs by keeping macroalgae under control