8/15/2012 12 th International Coral Reef Symposium, July 2012 Key - - PDF document

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Algal growth and coral recruitment: distinguishing fish and urchin effects

Wendy A. Cover, Donald C. Potts University of California Santa Cruz Fagatele Bay National Marine Sanctuary 12th International Coral Reef Symposium, July 2012

competition

Key interactions on coral reefs

indirect effect herbivory competition

Key interactions on coral reefs

herbivory indirect effect competition

Key interactions on coral reefs

herbivory indirect effect

The details

specific roles relative importance strength of interactions

Hawaiian Archipelago

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Midway Atoll

protected intact high-latitude

The primary “herbivores” How do fishes and urchins differ in their effects on macroalgal growth and coral recruitment?

? ?

How do fishes and urchins differ in their effects on macroalgal growth and coral recruitment?

vs.

Factorial design

deployed for 11 mo. Algal biomass Algal species composition Coral recruitment

Methods

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Fish grazing prevented macroalgal growth Higher urchin densities remove more macroalgae Higher coral recruitment with fish Higher coral recruitment despite higher sediment Direct, negative relationship between macroalgae and coral recruitment

p = 0.018

Summary

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Conclusions

Fishes are the dominant herbivores on Midway Fish grazing indirectly promotes coral recruitment Every little bit helps: any reduction in macroalgal cover should allow for more coral recruitment

Acknowledgments

Funding:

U.S. Fish and Wildlife Service, Midway Atoll Mitsubishi Corporation (Tokyo) – Global Coral Reef Conservation Project EEB Department National Fish and Wildlife Foundation CDELSI Packard Foundation GANN UCSC Center for Remote Sensing Lawrence Livermore National Labs

Field, Lab, and Analysis help:

Kate Schoenrock, Kristin McCully, Anne Warner, Mike Richardson, Thomas Omolo, Mark Carr, Jim Estes, Mike Graham, Pete Raimondi