CAMBIAMENTI NELLA STRUTTURA DI POPOLAZIONE DI CORALLIUM RUBRUM (L., 1758) NELL’AREA MARINA PROTETTA DI PORTOFINO SU SCALA PLURIDECENNALE

CHANGES IN THE CORALLIUM RUBRUM (L., 1758) POPULATION STRUCTURE WITHIN THE MARINE PROTECTED AREA OF PORTOFINO ON A MULTIDECADAL SCALE

Abstract

The red coral (Corallium rubrum) population in the Portofino Marine Protected Area has been monitored since 1964, when Marchetti conducted the first survey, providing a baseline for long-term comparisons. The original sampling protocol, which recorded minimum depth at 40 sites and collected quantitative data, was replicated 60 years later. C. rubrum was still present in nearly all historical sites and in seven new ones. The average minimum depth remained stable at around 26.5 m. However, after decades of increasing mean biomass—from 300 to 1500 g m⁻²—this value sharply declined over the past decade to approximately 450 g m⁻², without a corresponding rise in colony density. The average colony weight returned to levels recorded in 1964. This decline likely reflects the combined effects of global environmental change and local disturbances, including the extreme storm event of 2018, which severely impacted the coral populations along the Portofino Promontory.