The role of disturbance in differential regulation of co-occurring brown algae species: Interactive effects of sediment deposition, abrasion and grazing on algae recruits

Disturbance is an important structuring factor in intertidal communities. This study aimed at experimentally testing the effects of three important sources of disturbance to intertidal rocky habitats (abrasion, sediment deposition and herbivory) on the survivorship and growth of embryos of canopy forming fucoid species (Fucus vesiculosus and Fucus serratus). Natural levels of sediment deposition and herbivore density were characterized and the temporal variation of populations of both species was followed. The experimental study showed that the survivorship of F. serratus embryos was negatively affected by herbivory but growth was enhanced in the presence of abrasion and herbivores. F. vesiculosus suffered the interactive negative effects of the three sources of disturbance tested, although abrasion was the most important factor affecting mortality rates of embryos. Conversely, none of the tested sources of disturbance significantly affected growth of embryos. These results highlight the importance of disturbance events in regulating species interactions which might be particularly relevant for population dynamics and persistence at the geographical borders of species' distribution.

► We studied the effects of disturbance in marginal populations of fucoids.
► Sources of disturbance used were sedimentation, abrasion and herbivory.
► Response variables were survival and growth of F. serratus and F. vesiculosus embryos.
► F. serratus growth was enhanced by abrasion and herbivory that also affected survival.
► F. vesiculosus survival suffered the interactive effects of all the disturbances.