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Marine Ecology Progress Series

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MEPS 299:45-54 (2005)  -  doi:10.3354/meps299045

Effects of disturbance on the diversity of hard-bottom macrobenthic communities on the coast of Chile

Nelson Valdivia1, Astrid Heidemann2, Martin Thiel1,3, Markus Molis4,5,*, Martin Wahl4

1Facultad de Ciencias de Mar, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile
2Institute for Biology and Environmental Science, Carl von Ossietzky University, Ammerländer Heerstr. 114–118, 26129 Oldenburg, Germany
3Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Coquimbo, Chile
4Leibniz-Institute for Marine Science, Düsternbrooker Weg 20, 24105 Kiel, Germany
5Present address: Foundation Alfred Wegener Institute for Polar and Marine Research, Biological Station Helgoland, Kurpromenade 201, 27498 Helgoland, Germany
*Corresponding author. Email:

ABSTRACT: The intermediate disturbance hypothesis (IDH) predicts maximal diversity at intermediate levels of disturbance, but the validity of this hypothesis is controversially discussed. In this study, results of a field experiment, which was conducted on the northern-central Chilean coast, are presented. Fouling communities on artificial settlement substrata were studied. A total of 7 disturbance frequencies were applied to previously established communities, and a single disturbance event resulted in a removal of ~20% of the biomass. Species cover was estimated at the end of the experimental period, and it was found that diversity was strongly affected by disturbance frequency. With high disturbance frequencies the composition of the community was changed, with a decrease in the solitary ascidian Pyura chilensis (Molina 1782). The decrease of P. chilensis resulted in an increase of the colonial ascidian Diplosoma sp. A unimodal relationship between disturbance frequency and species richness was found, supporting the IDH. The results suggest that disturbance sustains diversity by reducing the abundance of the dominant species (e.g. P. chilensis), preventing competitive exclusion of the subordinate species, thus allowing subordinate species to re-emerge when competition is alleviated by disturbance. The results also suggest that these species show a trade-off between competitive and colonizing abilities, pointing to the existence of a competitive hierarchy. Therefore, the presence of competitive exclusion and disturbance-induced suppression of the dominant species remains a crucial mechanism, permitting species coexistence in the context of the IDH in the system studied.

KEY WORDS: Disturbance–diversity relationship · Intermediate disturbance hypothesis · Disturbance · Competitive exclusion · Frequency · Sessile · Hard-bottom · Pyura chilensis

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