Marine life and roughness:
examples from coral reefs and coasts

Clifford Hearn, Ph.D.
Oceanography, UNSW, Canberra, ACT 2600, Australia

Wednesday, April 24, 2002
3:00 p.m.–Pacific Forum

Roughness in the ocean occurs at many spatial scales and generates turbulence that greatly affects marine life. A good example is a coral reef, one of the roughest surfaces in the ocean The extreme roughness of reefs causes currents and waves to dissipate energy at rates that far exceed values elsewhere in the ocean. Hence, the extreme roughness of reefs is the paramount reason that coral reefs can maintain high productivity in low nutrient tropical waters. Furthermore, causal relationships between nutrient-uptake rates and dissipation of energy support general observations on reef zonation and reef metabolic rates. Turbulence is also generated by the large-scale roughness associated with the coastal margins and assists coastal trapping of many types of larvae. Most roughness, and associated particle trapping, is accentuated by oscillatory motions such as waves (on reefs) and tides (on the coast). A good example is the eutrophication of the North Sea.

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