The matrix influences direct and indirect effects of an anthropogenic disturbance on marine organisms.

The magnitude and direction of direct and indirect effects of disturbances can be context-dependent, with the matrix (surrounding habitat) in which populations are embedded either mitigating or worsening the impacts of disturbances. Chemical disturbances are particularly harmful and can affect organisms directly or indirectly. We used bleach, a common stressor in marine systems, to test hypotheses about direct and indirect effects of anthropogenic disturbances on intertidal grazers and the influence of the surrounding macro-algal matrix on such effects.

Macrofaunal responses to edges are independent of habitat-heterogeneity in experimental landscapes.

Despite edges being common features of many natural habitats, there is little general understanding of the ways assemblages respond to them. Every edge between two contrasting habitats has characteristics governed by the composition of adjoining habitats and/or by the nature of any transitions between them. To develop better explanatory theory, we examined the extent to which edges act independently of the composition of the surrounding landscape and to which transitions between different types of habitats affect assemblages.

Modified habitats influence kelp epibiota via direct and indirect effects.

Addition of man-made structures alters abiotic and biotic characteristics of natural habitats, which can influence abundances of biota directly and/or indirectly, by altering the ecology of competitors or predators. Marine epibiota in modified habitats were used to test hypotheses to distinguish between direct and indirect processes. In Sydney Harbour, kelps on pier-pilings supported greater covers of bryozoans, particularly of the non-indigenous species Membranipora membranacea, than found on natural reefs.

A continental scale evaluation of the role of limpet grazing on rocky shores.

It is critical for our knowledge of biodiversity and ecosystem processes to understand how individual species contribute to ecosystem processes and how these contributions vary in space and time. We used a manipulative field experiment in five locations over 17 degrees of latitude [from southern Portugal to the Isle of Man (British Isles)] to determine the relative response of rocky intertidal algal assemblages released from control by the grazing of limpets. Response ratios showed that when limpets were removed there was a trend of effects from north to south.