• climate change
• ecology
• temporal variance
• rocky intertidal
• life-history traits
• disturbance

This thesis was developed in the context of assessing the effects of temporal variability of disturbance events on organisms characterized by different life-history traits and recovery abilities. Two groups of high-shore rock pool organisms, characterized by contrasting recovery ability, were exposed to varying temporal regimes of mechanical disturbance differing for the time interval between consecutive events, while keeping the overall frequency of disturbance (total number of events applied over the time course of the study) constant over the period of the experiment. The target organisms were microphytobenthos (MPB) and filamentous algae (mainly Chlorophyta), examined to test the hypotheses that (i) close repetition of disturbance (20-day interval between consecutive events) would prevent the effective recovery of both groups; (ii) recurrent disturbance characterized by intervals of 40 days would allow the recovery of MPB, but not of green filamentous algae; (iii) the further extension to 80 days of the time interval between disturbance events would allow the effective recovery of both groups. The experiment was conducted using a total of 40 rock pools, distributed along about 1 km of coastline in Calafuria, south of Livorno. Concerning the data collection, percentage cover and frond length of filamentous algae were estimated using non-destructive methods. Regarding MPB, an indirect estimate of biomass was obtained through in vivo measurements of chlorophyll a fluorescence, using a Diving-PAM fluorometer. Separate asymmetrical ANOVAs were performed on the cover and the mean frond length of filamentous algae, and the biomass (F0) of MPB measured, in control and disturbed pools, in May 2021 and August 2021. Results indicated a difference between the unmanipulated pools and, on average, treated pools, while no difference among the three disturbance patterns, in almost all response variables examined on filamentous algae and MPB. Specifically, unmanipulated pools were characterized by a larger abundance of both organism groups compared to averaged treated pools, suggesting a negative effect of disturbance generally independent of the recovery time made available experimentally. Therefore, the initial hypotheses of this study were generally not supported, although filamentous algae showed a trend of partial recovery if disturbed every 80 days. Full recovery of this taxon would likely require a longer period than 80 days. With regard to MPB, the larger biomass observed in August compared to May could be attributable, at least in part, to the greater contribution made by cyanobacteria under more recurrent and prolonged desiccation conditions. In addition, large fluctuations in MPB biomass may be related to the bloom of their main grazers, namely littorinid snails.