Effects of trampling on intertidal mussel beds: importance of disturbance intensity

MENDEZ, MM; MENDEZ, MM; LIVORE, JP; LIVORE, JP; BIGATTI, G; BIGATTI, G

MARINE ECOLOGY PROGRESS SERIES

INTER-RESEARCH

Año: 2018

0171-8630

Trampling is one of the most frequent human disturbances on rocky shores. This activity may directly reduce the abundance of dominant species, indirectly promote changes in the abundance of associated species and ultimately affect biological interactions. We assessed the effects of different intensities of human trampling on Brachidontes spp. mussel beds, a dominant feature on rocky intertidal flats of the southwestern Atlantic coasts. To address this main goal, we experimentally applied 6 levels of trampling intensity on a Patagonian rocky shore. Simulated trampling intensity ranged from 0 to 600 tramps d1 and plots were disturbed replicating local usage patterns (i.e. austral summer weekends). By the end of the experiment Brachidontes spp. coverage was decreased by increasing intensities of trampling and mostly replaced by bare rock. Even the lowest experimental intensity produced a loss of more than 40% of coverage. Changes in coverage were generally immediate and occurred after the first 2 trampling events, regardless of disturbance intensity. Our findings highlight that as few as 5 people walking on the mid intertidal can produce a decline of the mussel bed cover in a specific area. They also alert to the urgency of implementing effective management actions in this and other frequented areas dominated by similar habitat-forming species.