Phase shift on temperate reefsMacroecology

Craig Johnson¹, Steve Dudgeon², Scott Ling¹, Simon Wotherspoon³

¹University of Tasmania, Australia - ²California State University, USA - ³Australian Antarctic Division, Australia

Phase shift is a well-established concept in ecology. It is highly relevant to study of the dynamics of temperate reefs, but while the theory is well documented, in some cases application of the concept to field observation suggests there remains a level of confusion about the details. We will clarify some common mistakes of interpretation in the application of the phase shift concept to temperate reef dynamics, briefly summarise the complex nature of experiments required to fully investigate phase shift and outline alternative approaches to studying phase shift using modelling approaches based on empirical parameterisation. We also address the question of whether it is necessary to understand quantitative details of phase shift to invoke meaningful management responses. While the vast majority of work in this space has focused on phase shift dynamics with two community states, we emphasise (i) that some systems are likely to have more than two alternative persistent states and, (ii) using examples from the Tasmania kelp-bed system, that multiple manifestations of phase shift dynamics may occur at different scales within a single assemblage type.