Abstract
Rocky intertidal platforms at Asinara Island Marine Protected Area (Italy, Mediterranean Sea) were experimentally trampled to assess the impact of human visitation on polychaetes. Trampling at two different experimental intensities (60,120 steps/20x20 cm quadrat) and controls were applied at two locations (“no-entry, no-take” zones) of the MPA. One day after the experimental trampling, benthic samples were collected and the polychaetes counted and identified. Overall 1146 individuals were collected; Salvatoria clavata, Polyophthalmus pictus, Syllis prolifera, Amphiglena mediterranea, Fabricia stellaris, Platynereis dumerilii and Sphaerosyllis taylori were the most abundant species. Analyses of variance on all polychaetes and on each of the important polychaete species showed a significant higher abundance in controls than in trampled plots. Given the short-term decline in abundance, these results suggest that polychaetes are vulnerable even to the lowest experimental level of trampling.
Highlights
The wide range of anthropogenic disturbances influencing marine coastal assemblages is of increasing concern
Trampling at two different experimental intensities (60,120 steps/20x20 cm quadrat) and controls were applied at two locations (“no-entry, no-take” zones) of the Marine Protected Area (MPA)
Given the short-term decline in abundance, these results suggest that polychaetes are vulnerable even to the lowest experimental level of trampling
Summary
The wide range of anthropogenic disturbances influencing marine coastal assemblages is of increasing concern. Rocky intertidal communities are sensitive to disturbance from indirect agents, such as sewage and industrial effluents (Littler and Murray, 1975), and to more direct agents, such as harvesting and trampling Several studies have documented that these impacts affect the intertidal target species by inducing changes in abundance, decreasing species richness and shifting community composition (Siegfried et al, 1985, Keough et al, 1993, Dye et al, 1997; Fernandez and Castilla, 1997; Lasiak, 1998). Several types of impact are associated with trampling such as direct mortality or dislodgment of organisms, weakening of algal holdfasts and structural damage, resulting in both increased vulnerability of rocky communities to other abiotic (e.g. dessication) or biotic (e.g. predation) factors, and habitat loss, as sessile organisms are crushed or removed (Brosnan and Crumrine, 1994; Brown and Taylor, 1999)
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