Recovery potential of coral reefs in Madagascar and the role of marine reserves
Creators: name: Randrianarivo, Mahery
name: Gasimandova, Max
name: Tsilavonarivo, Johanès
name: Razakandrainy, Andriamanjato
name: Philippe, Jacques
name: Guilhaumon, François
name: Botosoamananto, Radonirina Lebely
name: Penin, Lucie
name: Todinanahary, Gildas
name: Adjeroud, Mehdi
Publisher: name: Zenodo
Year: 2022
Subjects: Coral assemblages
TOPSIS method
Recovery index
Marine reserves
Madagascar

description: Coral reefs around Madagascar have been impacted by various natural and anthropogenic threats over the last 50 years. These perturbations have caused the decline of scleractinian coral assemblages at several sites, in turn reducing the goods and services provided by coral reef ecosystems, which are essential to support local and national economies. To improve the health and resilience capacities of these reefs, Madagascar has been developing a considerable amount of marine reserves since the early 2000s. The positive effects of these marine reserves have been demonstrated for fisheries, but not for coral assemblages.In this study, we evaluated the recovery potential of coral assemblages at 18 sampling stations, located in three regions around Madagascar (Masoala in the NE, Nosy-Be in the NW and Salary Nord in the SW). To determine the effect of marine reserves, three of the stations at each of the regions were located in fished areas and three in unfished areas. We used the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS), a widely used multi-criteria decision-making analysis, to calculate a recovery index (RI). Generic richness, densities of juvenile and adult coral colonies, coral cover (including stress-tolerant taxa), algal cover (turf and macroalgae), herbivorous fish biomass and sea surface temperature anomalies (SSTa), each considered as key factors of coral reef resilience, were included in the RI.Results showed that coral generic richness and algal cover were similar among the three regions, whereas coral density (total and juvenile) and herbivorous fish biomass were higher in Masoala, and coral cover (of all and for stress-tolerant taxa) reached higher values at Nosy-Be. SSTa were most frequent in the west coast (Nosy-Be and Salary Nord). At the regional scale, the highest RI was recorded at Masoala (0.48), followed by Nosy-Be (0.36) and Salary Nord (0.32). At the station scale, the highest RIs (> 0.50) were found in three stations at Masoala, whereas lowest RIs (< 0.30) were found at one station in Nosy-Be, and four stations in Salary Nord. The effect of marine reserves (estimated by the difference between RIs in unfished andfished stations) was significant at Nosy-Be (RI = 0.16), but not at Masoala (RI = 0.04) or Salary Nord (RI = 0.01).We suggest that the lower frequency of SSTa found along the east coast of Madagascar can be one of the factors explaining the higher recovery potential obtained at Masoala. In contrast, the combination of more frequent SSTa and higher anthropogenic pressures on the west coast results in lower recovery capacities in Salary Nord and Nosy-Be. The accessibility, size and age of marine reserves likely play a role in their success as well. Our study also highlights the usefulness of the TOPSIS method to estimate recovery capacities of coral assemblages, which can be an effective and accessible tool to improve the conservation and management of coral reefs