The influence of trampling disturbance on the fluorescence and pigment concentration of Sargassum beds (Fucales)

Direct and indirect effects on ecological processes caused by natural and anthropogenic disturbances may alter the composition and relative abundance of marine benthic communities. Trampling is a source of impact that can lead to the removal of individuals, breakage or damage of structural components and alterations of physiological performance of sessile organisms, possibly affecting the population dynamics and indirectly promoting structural changes in the entire community. To better support management strategies for coastal environments and to evaluate the anthropogenic impacts on a seaweed bed dominated by species of the genus Sargassum inhabiting the subtidal rocky shores in southeastern Brazil, we used an experimental approach to assess the physiological responses of this seaweed to trampling. We applied different intensities of trampling expected during summer vacation and throughout different periods of the year and quantified the fluorescence and pigment concentration of Sargassum beds. Changes caused by trampling are reflected in the health status of Sargassum, showing a decrease in chlorophyll a fluorescence and concentration of photosynthetic pigments depending on the site where this kind of impact occurs.