Megafauna of the RMS Titanic shipwreck and a nearby seamount ridge in the deep sea of the western North Atlantic

The biology of shipwrecks and hard substrata in the deep sea remains poorly explored. These complex habitats alter biodiversity on the deep seafloor and facilitate connecting populations over large distances. We analysed biological and environmental data collected at the RMS Titanic wreck site (3800 m) and a seamount ridge (2900 m) during the 2022 Titanic Expedition (15 June–25 July). The ridge is part of Seamount U, approximately 40 km southeast of the Titanic, and was explored for the first time on July 23, 2022. We analysed megafaunal occurrence across 920 images of the wreck site and 169 images of the ridge site, from digital video. The most common megafauna overall were Ophiuroidea, Munidopsis sp., Cushion-Encrusting Porifera, Geodia spp., and cold-water corals including Keratoisididae and Pennatuloidea. We describe the patterns in community composition across five benthic habitats, likely controlled by substrate type, local hydrodynamics, and food availability. The ridge yielded a higher number of observed megafauna and higher Shannon diversity (n = 73; H = 2.89) than the wreck (n = 21; H = 1.39). The communities associated with the ridge showed high dissimilarity to those at the wreck. We also explored the temporal variability of biofouling organisms on the Titanic using video from 1986 to 2022. We observed a net increase in Chrysogorgia sp. and Lepidisis sp. coral colonies over time with estimated average linear growth rates of up to 10 mm/yr and linear rusticle extensions of up to 14 mm/yr, raising questions about the wreck's ecological succession as it deteriorates.