Bottom current velocity

Bottom current velocity can affect abundance and biodiversity of benthic fauna by altering disturbance regimes, changing available habitats, and regulating nutrient flows. The intermediate disturbance hypothesis predicts maximum biodiversity at a frequency of disturbance where recruitment is able to replace lost individuals but inter-specific processes don’t have time to exclude species (Connell 1978). Thus, highest biodiversity will be generally associated with occasional episodes of strong bottom current velocity (e.g. bed shear stress on GBR in (Pitcher and Centre 2007)). Bottom current velocity can interact with substrate type to affect biodiversity, with sediment stability dependent on slope, particle size and the degree of water motion on the bed (Bagnold 1963). For example, mobile sandy or fine gravel substrates in strong currents typically show much lower richness.

Strong bottom current velocities may contribute to primary space being made available by increasing sheer stress which can remove sediment and expose hard substrate or by mechanical abrasion or damage caused by moving sediment or projectiles (Sousa 2001). Species composition often varies dramatically between consolidated (i.e. hard) and unconsolidated (i.e. soft) substrate (Williams and Bax 2001, Beaman and Harris 2007), with hard substrates generally acting as habitat to a larger proportion of sessile suspension feeders and soft sediments as home to infauna and a larger proportion of small, discretely motile invertebrates. Limited research exists on the effects of bottom current velocity on biodiversity in the North and North-West.

Use the interactive map below to explore how a related variable - sheer stress - vary around Australia's coastline.

How to use the map

	Click on this icon at the top left of the map to see a full screen version and legend.
	Click on this icon also at the top left of the map to zoom in closer to (+) or further from (-) the map.

References

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