Patterns of Herbivorv on Reefs 



Herbivory is greatest in shallow forereef habitats and reduced in shallow algal 

 ridge and backreef habitats. The reduced herbivory around massive algal ridges is 

 likely due to the absence of habitat and refuge space in those environments coupled 

 with the characteristic turbulence (discussed in Steneck and Adey 1976). Backreef 

 habitats are an enigma. They consistently indicate lower levels of grazing (both 

 intensity and frequency) but no simple explanation can be offered. The decrease in 

 herbivory with depth is not surprising since the trophic carrying capacity for 

 herbivores probably diminishes with depth as a function of reduced benthic 

 productivity (Steneck in prep.). 



Ecologists are far from agreeing on a method (or methods) for measuring herbivory 

 on reefs. While this does not seem to inhibit publications on the subject, 

 comparisons between reefs are impossible. The simplest and most easily replicated 

 technique, the Thai ass i a bioassay, is of dubious meaning and must be examined 

 critically in other comparative studies before its general application can be 

 accepted (see Hay 1983 for caveat). The only clear message revealed in this study 

 is that quantifying a process is infinitely more difficult than quantifying patterns 

 in the abundance of herbivores. So far we have only scratched the surface and still 

 we are biting off more than we can chew. 



ACKNOWLEDGEMENTS: 



This project was funded by a grant from NOAA NA82AAA01460 for Hydrolab mission 

 82-6. D. Blanchard, S. Brusila, R. Carpenter, D. Cancilla, D. Estler, E. 

 Fleishmann, M. Hay, L. Mayer, B. Milliken, D. Morrison, J. W. Porter, and L. Schick 

 assisted in various phases of the study. 



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