Extinction risk of the endemic soft coral Phyllogorgia dilatata (Esper, 1806) in a remote island of the Brazilian coast

The Brazilian endemic octocoral Phyllogorgia dilatata (elephant ear sea fan) plays a crucial ecological role in the marine ecosystems of the Brazilian coast. Our work investigates the local extinction of P. dilatata on Trindade Island, a remote oceanic island in the Southwestern Atlantic, and assesses the potential impacts of climate change on its distribution. Field surveys conducted over two years (2016-2019) revealed no live individuals of P. dilatata, with only dead peduncles remaining, marking the first observed local extinction of this species. Species distribution models (SDMs) incorporating current and historical climate data were used to estimate the species' habitat suitability and project future distribution under different climate scenarios. Results indicate that P. dilatata currently inhabits approximately 93,090 km2 of suitable area, primarily within tropical ecoregions, but faces significant habitat loss under future climate projections. By 2090-2100, models predict a 63.38 % loss of habitat under the high-emission RCP 8.5 scenario, with severe impacts on tropical regions, including Trindade Island. Environmental variables such as temperature, oxygen concentration, and salinity were identified as key drivers of the species' distribution, while non-climatic factors like seawater velocity, were also significant. The extinction on Trindade Island is attributed to a combination of historical isolation, climate change, and local anthropogenic stressors, including pollution and overfishing. The current investigation highlights the urgent need for conservation efforts, including the establishment of marine protected areas and restoration programs, to protect this vulnerable species and similar marine organisms again climate change.