Seminars

Seminar Abstract

Friday 17 March 2006, 11.30am (Tas time) CSIRO Auditorium, Hobart Dr Phillip England CSIRO Marine and Atmospheric Research

Modelling waves and benthic habitat in WA coastal waters: does the intermediate disturbance hypothesis apply in reef macroalgal communities?

Habitat modelling in terrestrial systems is well advanced. However, understanding how environmental factors help determine marine community dynamics is a relatively new and challenging endeavour. One of the dominant benthic habitats in shallow coastal waters off southwest Western Australia is macroalgae-covered rocky reef.

Due to its likely importance, the influence of hydrodynamic forces on benthic habitat has been the focus of the SRFME habitat modelling effort. We tested whether the conspicuous fine-scale variability and high diversity in reef communities is driven by wave-induced physical disturbance. The complex topography found in reef zones makes the task of characterising the hydrodynamic forces experienced by benthic organisms challenging.

Our approach has been to use the numerical, spectral wave model SWAN forced with local wave and wind conditions in fine-scale bathymetric domains. Predicted patterns of the oscillatory surge experienced at the seabed were used as an index for physical disturbance in macroalgal habitat. Storm-generated extremes were modelled and compared with measured benthic community attributes at 26 reef sites near Jurien Bay.

Consistent with the Intermediate Disturbance Hypothesis, macroalgal species diversity appeared to be highest at sites which experience intermediate levels of wave generated surge during extreme events. Diversity was lower at exposed, offshore sites and at very sheltered sites. Results from other highly diverse habitats, including rainforests, grasslands and coral reefs, and from computer models indicate that patchy, stochastic disturbance regimes prevent the development of homogeneous climax communities in which small number of highly competitive species prevail. Spatiotemporal heterogeneity increases total system diversity and there is an intermediate level of disturbance at which the biodiversity of the system as a whole is maximised.

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CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
Karen Wild-Allen, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5010
Piers Dunstan, (Biological seminars) CSIRO Marine and Atmospheric Research (03) 6232 5382
Sandra Zicus, Antarctic Climate and Ecosystems CRC (03) 6226 7888 & Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2509