Changes in the Structure of the Bacterial Community Associated With <i>Ericaria amentacea</i> Blades Under Disturbed Conditions

The macroalgae of the <i>Cystoseira sensu lato</i> 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 <i>Cystoseira sensu lato</i> 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 <i>Cystoseira</i> complex were evaluated in the three main islands of the MPA, characterized by different levels of protection. Moreover, thalli samples of the target species <i>Ericaria amentacea</i> (C. Agardh) Molinari and Guiry were collected in each zone to quali-quantitative characterize its associated bacteria. Results confirmed a high abundance of <i>Cystoseira sensu lato</i> 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 <i>Lutibacter</i> and <i>Psychromonas</i>, was observed. These results prove that the structure of the bacterial community associated with <i>E. amentacea</i> 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.