Coral reef - Hard structure with live coral, gorgonians, sponges etc. - ecosystem component from the WIO Symphony tool

A number of coral data sources in the WIO region and globally were combined, and a new predictive model was constructed for the Saya de Malha Banks where sparse observations but no map excisted. The maps were ranked by quality and adjusted and combined based on ranking, and information from overlapping higher resolution maps. The major steps included: (1) Mapping the Allen Coral Atlas coral polygons presence to a 250-m grid, then calculating the proportion of 250-m presence pixels within each 1-km pixel. Further, total map footprint proportions were mapped to 1-km pixels (2) Same process as (1) for two additional high-resolution maps: Corals in Chagos and Seychelles from the Khaled bin Sultan Living Ocean Foundation (3) The Global Coral map from the WCMC portal was mapped same as (1), but due to variable spatial resolution and accuracy it was adjusted with a coefficient calculated by comparing the mean cover in the Allen Atlas 1-km map with the WCMC 1-km map. (4) A 2008 coral map for Madagascar was retrieved from the African Marine Atlas through the Ocean Info HUB project. It was mapped similar to (3), by adjusting coverage to a coefficient by comparing with the higher resolution Allen Coral reef map. (5) A BRT machine learning model was developed for the Saya Del Mahla Bank, modelling coral coverage based on % cover data published by Ramah S. et al. The model uncertainty is high, but predicts coral in regions of the banks known to have coral (personal conversation Dr. Rawat and others) which are currently not available in any open maps. (6) All maps were mosaiced together in order of their ranking, using map footprint to mask out lower ranked maps, then choosing the max value in the remaining overlap. Known limitations: The coral reef map combines all open sources of coral reef data, and also uses some creative solutions to put coral reef on the map where data was missing (low confidence modelling of Saya del Mahla banks) to put known but unmapped reef areas in the tool. The quality of these maps varies greatly across the region and also it is likely that many reefs are missing in the deeper areas 20-40m since the most comprehensive data set (ACA) has a depth limit of 15-20 meter. Though this map represents the best-known information of coral reef it needs to be used with care, especially when activities that can harm coral reefs are planned. Further studies and mapping efforts are needed.