Impacts of disturbance on the dynamics of marine benthic communities

Abstract

Disturbances are one of the most important factors in maintaining the coexistence of species, and their frequency, intensity and timing are all thought to be increasing as a direct consequence of anthropogenic global change. Therefore many species may not be able to adapt and may subsequently be lost from an ecosystem. The aim of this thesis is to focus on the local scale processes in benthic subtidal habitats that are thought to drive the co-existence of species within communities. The primary goal was to investigate disturbances and their impacts upon temperate marine benthic communities, and secondary aims explored the interactions between disturbances, productivity and habitat complexity. In order to test the intermediate disturbance hypothesis and a model of disturbance-productivity interactions, communities of two different successional stages were manipulated with a range of disturbance frequencies and varying levels of nutrient availability. The effect of temporal variation around the disturbance regime which caused the greatest effect, as well as the sequence of these disturbances, was then investigated. Finally the role of natural surface heterogeneities in creating refuges in the face of a suite of different disturbances was investigated, and used to discover the value of increasing habitat complexity in maintaining or promoting diversity. Results from all experiments have shown that disturbances are important structuring forces for benthic marine communities. Disturbance-productivity interactions do not support the intermediate disturbance hypothesis or the disturbance-productivity model and the temporal variability of disturbance regimes appears to be an unimportant factor in the structuring of these temperate communities, whereas increased habitat complexity provides important refuges in the presence of abiotic disturbances.