The underwater exploration of the Merro sinkhole and the associated diving physiological and psychological effects

The Pozzo del Merro (Merro sinkhole), a few kilometres away from Rome, Italy, is the deepest flooded karstic cavity known in the world. Over the last two years, a multi-disciplinary scientific research project studied the almost unknown aquatic ecosystem of the sinkhole while also studying the psychological and physiological reactions of scientific divers operating in the very hostile underwater environment. This paper presents a preliminary overview of the seven studies carried out in parallel and attempts to highlight the fundamental role of scientific diving in contributing to increased knowledge about this extreme environment. The discovery of two exotic species in the sinkhole represents a paradigmatic case of the problem of invasive species introduction in such a unique environment. The project also included research on human diving physiology, pathology, and psychology through monitoring of all the divers (plus one free-diver) working in the Merro sinkhole.