PowerPoint Presentation

Herbivory and sea urchin predation

for ecosystem resilience

By Charlotte Johansson, David Bellwood and Martial Depczynski

Introduction

Coral reefs under pressure

Human impacts

Increasing disturbance to reefs

Loss of vital functions (ecologicalroles)

Gradual erosion of resilience

Introduction

Resilience

“the capacity of a system to absorb disturbance and reorganizewhile undergoing change so as to still retain essentially thesame function, structure, identity and feedbacks”

(Walker et al 2004)

To understand how ecosystem processes will be affected bydisturbances we need to look at the species that contribute tothem and what the strength of their combined functional role is

Introduction

Functions are;

Processes (feeding) – movement orstorage of materials or energy(Bellwood et al 2004)

Functional groups;

A collection of species that perform orinfluence the same function,irrespective of their taxonomic affinities(e.g. herbivores, nitrogen fixers etc)(Bellwood et al 2004)

Introduction

4 roving herbivorous groups

Macroalgae

Browsers

Grazers

Scrapers

Excavators

Herbivores

Turfalgae

Introduction

Fine scale approach when evaluating resilience:

1.Alternative organism (coral/algae)

2.Herbivorous fish

Functional redundancy (same functional role)

Functional diversity (different functional role)

Responses

3.Non-fish herbivores (sea urchins)

Aim

1.Quantify the distribution of:

Macroalgae

Herbivorous fish

Non-fish herbivores (sea urchins)

2.Evaluate the extent to which herbivorous fish and urchins arelikely to control macroalgae

Study location

Ningaloo Reef, Western Australia

1. Alternative organisms

2. Herbivorous fish

Density of herbivores

2. Herbivorous fish

Abundance (%)

Grazers

Excavators

Lagoon

Back

Slope

3. Non-fish herbivores

$F:\PhD Photos\New fishy Pics!\3Mile Lagoon 5.7.09 Bridled Parrotfish Female MF 198.jpg$

$F:\PhD Photos\Ningaloo\Fish Library Ningaloo 2009\Echinodermata\M0018713.JPG$

3. Non-fish herbivores

Important role on Ningaloo Reef

What is driving the pattern ofurchins, especially on the slope

Is it a lack of predators?

Urchins = reef degradation

$F:\PhD Photos\Ningaloo\Trip N February 2011\Night urchins\IMG_3125.JPG$

$F:\PhD Photos\Ningaloo\Trip N February 2011\Night urchins\IMG_3133.JPG$

3. Non-fish herbivores

$C:\Users\charlotte\Documents\PhD\Conference\AIMS@JCU Symmposium April 2011\C rubescens.jpg$

$C:\Users\charlotte\Documents\PhD\Conference\AIMS@JCU Symmposium April 2011\Coris aygula (3).jpg$

$F:\PhD Photos\Ningaloo\Trip N December 2009\18_12_2009\Urchins\R0081402.JPG$

$F:\PhD Photos\Fish ID\Balistidae\Balistapus undulatus.jpg$

3. Non-fish herbivores

0.640

0.537

0.423

Conclusion

Macroalgae abundant in lagoon (despite herbivores)

Urchins abundant on slope (despite predators - except specialistbalistids)

Urchins and algae often signs of degradation - here they appearto not be

Ningaloo Reef, although relatively intact, appears to befunctionally distinct to other reef systems

Acknowledgements

Prof D. Bellwood, Dr. M. Depczynski,Dr. A. Hoey and I. van de Leemput

JCU, ARC Centre of Excellence

AIMS, AIMS@JCU, DEC

Colleagues in the lab and field