Léo Broudic (leobroudic@proton.me)
Biodiversity Research Agency of La Réunion (ARBRE)
UMR 6553 University of Rennes CNRS - ECOBIO, Rennes, France
IRN APOLIMER - Sciences Po CNRS CEVIPOF Chaire Outre-mer, Paris, France
Abstract
Faced with the need to spatialise the ecological issues of coral reefs and associated ecosystems, the French Coral Reef Initiative (IFRECOR) started in 2014 to develop an approach to map coral reefs, seagrass beds and mangroves. The aim was to find a field method that is simple, fast and translates coral reef heterogeneity spatially through several ecological metrics. A compromise had to be found between the size of the station, the time to need to assess each station, the possibility of replicating and the quality of the data. Based on the existing methods and scientific literature, we proposed the COral Reef Assessment Method (CORRAM), the SEAgrass Assessment Method (SEARAM) and the MANgrove Assessment Method (MANRAM). For example, CORRAM has two field protocols, one for the benthic community and a second one for the mobile fauna. For benthic communities, a station has a circular plot of 100m2 where nine quantitative metrics (i.e. live coral cover, fleshy algae (>2cm), structural complexity, etc.) are assessed by visual estimation. For the mobile fauna, one station has a square of 2 500m2 for 10 minutes where four quantitative metrics (i.e. fish diversity, abundance and maturity of scarids and top predators, and abundance of holothurians) are evaluated with a GPS tracking. The UTOPIAN project, in Reunion Island was designed to improve CORRAM by mapping the coral reef from the reef flat to the outer slope (-15 m in free dive). The sampling effort was of 1.6 station.ha-1 in the outer slope and of 7.6 station.ha-1 in the reef flat. The data were interpolated using geostatistical analyses (ordinary kringing) and a map of each metric was produced for each reef unit. The map is a raster layer, so we calculated the ratio area of each category of each metric (i.e. for the whole Saint-Leu reef, we have 19% ± 20% live coral cover, and 19% of the reef has a live coral cover between 6 and 15%). We can change the scale from mesoscale (unit reef) to macroscale (reef habitat) and to calculate the mean of each metric by habitat (choropleth map). The UTOPIAN project has shown that the map is an attractive tool for public authorities and managers, especially for the development of spatial planning or management plans. The scientific publication is in prep, and an important information is that the sampling plan can be reduced while maintaining the same quality of spatial interpolation (map), making the method replicable over time. You can read more about CORRAM and UTOPIAN here: https://ifrecor.fr/utopian-et-letat-ecologique-des-recifs-coralliens-de-la-reunion/
Power point presentation :
