Spatial ecology of two emblematic deep-sea crustaceans in the Salas y Gómez, Nazca and Juan Fernández ridges Southeast Pacific.

The Salas & Gómez, Nazca, and Juan Fernández ridges are among the least studied regions on the planet. Ecological knowledge of deep-sea organisms inhabiting islands and seamounts along these ridges is limited. Using various sources, including published data and in situ information from five scientific expeditions in the region, we analyzed the spatial ecology of Paromola rathbuni and Projasus bahamondei, two mobile species of benthic megafauna. Random Forest models detected different combinations of abiotic variables affecting species distribution. The distribution of P. bahamondei was primarily influenced by dissolved oxygen, longitude (W), and temperature. The distribution of P. rathbuni was mainly explained by longitude (W), followed by depth, temperature, and oxygen. Generalized Linear Models quantified significant effects of low dissolved oxygen and temperature on species presence, influencing their preference for bathymetric ranges (P. bahamondei at 400-500 m, P. rathbuni at 300-400 m). A distribution break to the west of ~ 85°W was confirmed, potentially due to the weakening of the Oxygen Minimum Zone altering oxygen and thermal conditions. This feature could act as a barrier for both species despite their high dispersal potential. Under projected climate change, shifts in latitudinal, longitudinal, and bathymetric distribution patterns are expected for both species.