Stuckrad, Sae Kyung von (2006) Effekte von zeitlich variierender Störung auf die Diversität mariner Hartsubstratgemeinschaften. (Diploma thesis), Humboldt-Universität zu Berlin, Berlin, Germany, 58 pp.

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Abstract

Diversity refers to all aspects of variety on the living world. Several models exist explaining diversity and the coexistence of species. One of the most controversial discussed models is the IDH (Intermediate Disturbance Hypothesis) which identifies disturbance as the source of diversity. Disturbance has an effect on community compositions. Disturbance can be applied on a certain frequency, meaning a distinct number of disturbance events take place in a defined period of time. The following study tested the effects of the temporal order of disturbance events on community composition. This temporal order was called the sequence of disturbance events. Artificial settlement substrata were exposed to colonisation by marine organisms and communities were manipulated by disturbance frequency in a multi-factorial design. The experiment was set up in the Pacific Ocean in Wollongong Harbour, an artificial wave sheltered bay at the East Cost of Australia. After 150 days of manipulation species richness, total abundance and percent cover of all species in a community were recorded and wet and dry weight measured. Communities were dominated by algae, especially red algae. Disturbance influenced species richness, evenness, total abundance and biomass of the communities. In general disturbance reduced the number of species. Single species reacted differently to the disturbance treatments. Weak competitors were enhanced trough disturbance and dominant species were reduced. Contrarily to expectations of increasing diversity and heterogeneity of communities with increasing variability and of differences among communities that experienced different sequences, no unimodal effect of variability could be observed.

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