Abstract
The macroalgae of the Cystoseira sensu lato complex host a great epiphytic bacterial community that significantly guarantees several important physiological processes, especially in case of disturbance. However, no direct evidence of relevant changes in the quali-quantitative composition of these communities under anthropic disturbance is currently available. This work aims to characterize the epiphytic bacterial community associated with Cystoseira sensu lato populations in case of disturbance in Tavolara Punta Coda Cavallo Marine Protected Area (Sardinia, Italy). To this purpose, the abundance and health status of the most abundant species of the Cystoseira complex were evaluated in the three main islands of the MPA, characterized by different levels of protection. Moreover, thalli samples of the target species Ericaria amentacea (C. Agardh) Molinari and Guiry were collected in each zone to quali-quantitative characterize its associated bacteria. Results confirmed a high abundance of Cystoseira sensu lato populations in the whole study area, with no chlorosis or damages related to the magnitude of disturbance. Significant differences were instead recorded in the quali-quantitative characterization of the bacterial community among islands. Where the protection was lower, the abundance of living bacteria was higher and a relevant presence of bacteria involved in macroalgae resistance to disturbance, such as Lutibacter and Psychromonas, was observed. These results prove that the structure of the bacterial community associated with E. amentacea blades significantly changes in relation to disturbance. Moreover, they suggest that the good health status of these macroalgae observed also in cases of quite high disturbance could be related to a shift in its epiphytic bacterial community composition, that could, therefore, be actively involved in their adaptation.