Indirect Effects Alter Coral Community...

Indirect Effects Alter Coral Community Composition

Jada-Simone S. WHITE3 March 2009

Pacific Science Intercongress, Tahiti

SEMINAR FORMAT

I. Introduction

II. Experimental Test of Mechanisms

III. Demographic Context

IV. Implications

Introduction Mechanisms Demographics Implications

Ecosystem engineers create, modify, or maintain habitats. (Jones et al. 1994)

Stegastes nigricans

Dusky Farmerfish


Stegastes can be a KEY Engineer

Habitat Modification

Combination of strong direct and indirect effects

Effects will vary among species

Both positive and negative consequences for species that inhabit the new and old habitat, respectively


How can Stegastes modify coral composition?


Per

cen

t L

ive

Co

ral

00.10.20.30.40.50.60.70.80.9

1 Stegastes PRESENT Stegastes ABSENT

Type of Reef (N=25)

LIVE Porites


ALGAL TURF

Per

cen

t A

lgal

Tu

rf

0

0.2

0.4

0.6

0.8

1 Stegastes PRESENT Stegastes ABSENT

Type of Reef (N=25)


BRANCHINGEPICORAL

0

5

10

15

20

25

30

35

40

45

50

Other Acropora Montipora Pocillopora

Stegastes PRESENT Stegastes ABSENT

Nu

mb

er o

f E

pic

ora

ls

Type of Epicoral

Data from Done et al. 1991 (Coral Reefs)Introduction Mechanisms Demographics Implications

Stegastes reefPhoto Credit: J.L. O’Donnell


SIMPLE LAGOON COMMUNITY

StegastesStegastesStegastesStegastes Coral PredatorsCoral PredatorsCoral PredatorsCoral Predators

CoralsCoralsCoralsCoralsTurfTurfTurfTurf

HerbivoresHerbivoresHerbivoresHerbivores


What mechanisms are responsible?


TurfTurfTurfTurfFarmingFarmingFarmingFarming

+

Stegastes promote algal turf

Farming behaviors(Reviewed in Ceccarelli et al. 2001)


CompetitionCompetitionCompetitionCompetition

–

Prediction 1:Competition with

farmed turf REDUCES coral growth &

survival


+

(Reviewed in McCook et al. 2001)


CorallivoresCorallivoresCorallivoresCorallivores

TerritorialityTerritorialityTerritorialityTerritoriality

–

(Galzin 1985; Letourneur 2000; White, unpubl. data)

Stegastes communally defend


–

Photos : M

yers 1999

HerbivoresHerbivoresHerbivoresHerbivores

Egg PredatorsEgg PredatorsEgg PredatorsEgg Predators

(Gleason 1996, Letourneur 2000)


Coral PredatorsCoral PredatorsCoral PredatorsCoral PredatorsTerritorialityTerritorialityTerritorialityTerritoriality

–

PredationPredationPredationPredation–

(Reviewed in Rotjan and Lewis 2008)



–

Prediction 2: Territorial behavior

interferes and REDUCES coral

predation

DefenseDefenseDefenseDefense+


–


EXPERIMENTAL DESIGN

Turf

REMOVED

Turf

PRESENTTREATMENT

Stegastes

REMOVED

Stegastes

PRESENT

Turf

ABSENTTREATMENT

StegastesABSENT 0

Stegastes ABSENT reefs served as a control

32 Stegastes Reefs

8 Non-Stegastes Reefs

(White and O’Donnell, in prep.)


Acropora

PoritesPocillopora

Montipora


Within each reef, 3 transplants of each

coral species randomly assigned:

3 Sub-treatments

Cage

Cage control

Open


EXPOSEDCAGED



–

RESULTS: Do Stegastes

effectively reduce reef access?



–


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Butterflyfishes Surgeonfishes Parrotfishes

Present Removed Absent

EFFECT OF TERRITORIALITYM

ean

Fo

rag

ing

Fre

qu

ency


a b ab a b a a b ab

* * *

*Tukey’s HSD: P<0.05



–

RESULTS: Does territorial behavior reduce coral predation?



–


Implications for predation frequency

Caging Effect:~ 300 x higher in absence of cageRange: 35.7 to 1000(Wald χ2 = 25.25, P<0.0001)Stegastes Effect:~ 100 x lower in presence of StegastesRange: 11.2 to 1000(Wald χ2 = 16.44, P<0.0001)

Caging Effect:~ 200 x higher in absence of cage Range: 26.3 to 1000(Wald χ2 = 26.20, P<0.0001)Stegastes Effect:~ 27 x lower in presence of StegastesRange: 3.9 to 200(Wald χ2 = 11.09, P<0.0009)

Logistic Regression



Av

erag

e C

han

ge

in D

aily

Mas

s (m

g*d

-1)

Skeletal loss due to predation

Acropora

Montipora

(White and O’Donnell, in prep.)Introduction Mechanisms Demographics Implications


–


–

Stegastes territoriality REDUCES predation for Acroporids (Acropora and Montipora)




–

RESULTS:Does farmed turf reduce

coral growth & survival?


+


Turf Effect:3.4 x more likely in presence of turfRange: 1.4 to 8.4(Wald χ2 = 7.41, P = 0.007)

Stegastes Effect:11.3 x higher in presence of StegastesRange: 1.3 to 101.3(Wald χ2 = 4.65, P=0.03)Caging Effect:3.4 x higher in absence of cageRange: 1.0 to 11.4(Wald χ2 = 3.90, P=0.05)

Turf Effect:7.1 x more likely in presence of turfRange: 1.4 to 36(Wald χ2 = 5.48, P=0.02)

Logistic Regression


Porites

Algal abundance predicted significant amount of variation in overgrowth for Porites (Linear Reg., F1,13=31.2, P<0.0001) and Acropora (F1,13=17.9, P=0.001),

…but not Montipora or Pocillopora



–


+

Yes. Farmed turf REDUCES coral survivalfor Porites and Acropora



–


+

Apparent synergistic effect of predationfor Montipora

–

Coral PredatorsCoral PredatorsCoral PredatorsCoral Predators

PredationPredationPredationPredation


How does Stegastes alter the rate of predation for in situ Acropora and Pocillopora?


June 2006:Tagged 16 Stegastes reefsAcropora (N=106)Pocillopora (N=234) June 2006

Re-sampling/ tagging recruits:March 2007July 2007 - REMOVALSMay 2008

Methods: Before-After-Paired-Design


MonitoringMeasured size (L, W, H)Estimated % overgrownNoted Presence / Absence:

Turf “chimneys”PredationBleachingVermetid snails

Photo-documented fate

Methods: Demographic Study

Jun2006

Mar2007

Jul2007

Apr2008


July 2007:Tagged 4 additional reefsAcropora (N=199)Pocillopora (N=392)

Paired reefs-duration of monitoring-Stegastes density-size structure of corals

Applied clove oil to each pair

Stegastes recovered on half

Methods: Demographic Study


RESULTS: Does Stegastes alter the rate of predation for Acropora and Pocillopora?


Before – After in situ Farmerfish Removals: PocilloporaBefore Removals

5-5917.81076REMOVED4-3513.3806PRESENT

RANGEMEANNUM

COLONIES

NUM REEFS

2006-07

Pre-Removal Present


Before – After in situ Farmerfish Removals: PocilloporaBefore Removals After Removals

5-5917.81076REMOVED4-3513.3806PRESENT

RANGEMEANNUM

COLONIES

NUM REEFS

2006-07

7-2718.41478REMOVED3-2714.91198PRESENT

RANGEMEANNUM

COLONIES

NUM REEFS

2007-08

Pre-Removal Present Post-Removal Present


Before - After in situ Farmerfish Removals: AcroporaBefore Removals After Removals

3-83.8236REMOVED1-114.7286PRESENT

RANGEMEANNUM

COLONIES

NUM REEFS

2006-07

3-187.5608REMOVED1-168.4678PRESENT

RANGEMEANNUM

COLONIES

NUM REEFS

2007-08

Pre-Removal Present Post-Removal Present


Results: AcroporaBEFORE Removals AFTER Removals


Results: Partial MortalityBEFORE Removals

AFTER Removals

BEFORE Removals

AFTER Removals

Pocillopora Acropora


Summary:

Stegastes indirectly enhances survival of branching corals

Enhanced recovery of Acroporids and Pocilloporids-suggests corallivores / grazers constraining recovery

Photo C

redit: S. G

eange


Implications

Intraspecific variation in response

Dominant massive Porites are vulnerable to overgrowth, thereby increasing available substrate

High foraging pressure inhibits recovery of Acropora and Pocillopora outside farmerfish territories

May represent changes in foraging populations


BRANCHINGEPICORAL

Per

cen

t C

ov

er E

pic

ora

ls

Percent Cover Stegastes TERRITORIES


Branching corals offer important habitat for many fishes

(Shima et al. 2006)


Future DirectionsUse population models to pinpoint vulnerable size

classes (e.g., Crouse et al. 1987)

Identify predictors of mortality using Generalized Linear

Mixed Models (GLMM) (Bolker et al. 2009)

Pinpoint responsible taxa using video / removals

Analyze historical and larger scale changes in fish and coral communities

(with Renè Galzin and Thierry Lison de Loma)

AcknowledgementsAcademic AdvisorsBen Bolker (PhD)

Gustav Paulay (PhD)

Craig Osenberg (MS)

Committee MembersColette St. Mary

Karen Bjorndal

Bill Lindberg

Brian Silliman

Field SupportJosh Idjadi Mai Maheighan

Jimmy O’Donnell Shelby Boyer

Nicole Price Lindsey Carr

Michael Way Melissa Schmitt

Shane Geange Adrian Stier

Adrien Delval Emily Vuxton

Idea ExchangeRene Galzin Thierry Lison de Loma

Serge Planes Yannick Chancerelle

Pete Edmunds Mehdi Adjeroud

Sally Holbrook Russ Schmitt

Funding Support

ISRS / OC Graduate Research Fellowship

American Museum of Natural History

American Society of Ichthyologists and Herpetologists Moorea BIOCODE

Merci ~ Mauruuru ~ Thank you

TiahuraBarrier

CORALLIVORES`

TiahuraBarrier

HERBIVORES`

TiahuraBarrier

CARNIVORES`

Effects of eugenol on coral health and growth

Tested five concentrations (solvent):

Control (seawater)7% Eugenol (seawater)

14% Eugenol (seawater)14% Eugenol (Ethanol)28% Eugenol (seawater)

Three species of coral:

Acropora striataPocillopora verrucosaPorites australiensis

Treatments applied weekly for 5 weeks

Schematic of Experimental Design

Effects of eugenol on coral growth

33% (± 7%)28% (seawater)

37% (± 6%)14% (Ethanol)

25% (± 9%)14% (seawater)

12% (± 13%)7% (seawater)

% GROWTH REDUCTION RELATIVE TO CONTROL

(±95% CI)

TREATMENT

(SOLVENT)

0

2

4

6

8

10

12

0%(Seawater)

7%(Seawater)

14%(Seawater)

14% (Ethanol)

28%(Seawater)

PE

RC

EN

T C

HA

NG

E IN

GR

OW

TH

Acropora striata

Pocillopora verrucosa

Porites australiensis

66% (± 11%)

75% (± 0.06%)

49% (± 19%)

9% (± 20%)

Pocillopora verrucosa

64% (± 18%)

71% (± 11%)

17% (± 17%)

0 (0)

Acropora striata

78% (± 10%)28% (seawater)

48% (± 21%)14% (Ethanol)

17% (± 25%)14% (seawater)

0 (± 21)7% (seawater)

Porites australiensis

TREATMENT

(SOLVENT)

Average % Increase in bleaching frequency relative to control (± 95% CI)

0 00

0.2

0.4

0.6

0.8

1

0% (Seawater)

7% (Seawater)

14% (Seawater)

14% (Ethanol)

28% (Seawater)

TREATMENT

FRE

QU

EN

CY

OF

BLE

AC

HIN

G

Effects of eugenol on coral health

Take home –

7% Eugenol in seawater relatively safe

Apply to both “Present” and “Removal” reefs

- let Stegastes recover on half

METHODSQuantifying Algal Abundance

0.17 (0.33)0.17 (0.33)0.25 (0.20)Absent

0.57 (0.19)0.45 (0.14)0.53 (0.21)Removed

0.75 (0.49)00.07 (0.08)PresentSiganidae

0.42 (0.18)0.09 (0.06)2.27 (0.84)Absent

0.57 (0.10)0.53 (0.08)3.31 (0.55)Removed

0.17 (0.09)0.18 (0.08)2.09 (0.66)PresentScaridae

0.17 (0.09)0.26 (0.07)5.25 (0.58)Absent

0.40 (0.09)0.44 (0.05)4.98 (0.47)Removed

0.17 (0.07) 0.14 (0.05)4.24 (0.52)PresentAcanthuridaeHerbivore

0.36 (0.30)0.26 (0.07)0.42 (0.23Absent

0.55 (0.14)0.52 (0.11)0.95 (0.27)Removed

0.23 (0.13)0.23 (0.11)0.83 (0.23)PresentChaetodontidae

00.29 (0.36)0.15 (0.10)Absent

00.50 (0.20)0.27 (0.11)Removed

0.03 (0.07)0.09 (0.10)0.32 (0.10)PresentBalistidaeCorallivore / Omnivore

0.14 (0.05)0.30 (0.05)1.83 (0.27)Absent

0.29 (0.04)0.45 (0.03)3.14 (0.39)Removed

0.12 (0.03)0.19 (0.03)2.10 (0.29)PresentOVERALL

MEAN FORAGING FREQUENCY

MEAN FREQUENCY ON

REEF

MEAN DENSITY

Stegastes nigricans

FAMILYTROPHIC STATUS

Table 1. Summary of densities, reef access, and foraging frequency for corallivorous and herbivorous fish families encountered during regular (every 5 d) surveys.


↑↑↑↑ OvergrowthOvergrowthOvergrowthOvergrowth


INSUFFICIENT DATAINSUFFICIENT DATAINSUFFICIENT DATAINSUFFICIENT DATA

INSUFFICIENT DATAINSUFFICIENT DATAINSUFFICIENT DATAINSUFFICIENT DATA

↓↓↓↓ CorallivoryCorallivoryCorallivoryCorallivory

LIMITATIONS

+ +

–POLYPS ONLY

+

–COMPLETED RESEARCH: CHAPTER 1

Overall pattern of recruitment across reef types (Jan - Aug 2006)

0.31 (± 0.14)0.31 (± 0.12)0.35

(±0.16)Average number of recruits per tile (95% CI)

3.25 (± 1.8)

87.5%

(7 / 8)

21.25%

(17 / 80)

26

Stegastes Absent

3.25 (± 1.5)3.75 (± 2.8)Average number of recruits per reef (95% CI)

100%

(8 / 8)

87.5%

(7 / 8)

Proportion of reefs with recruitment (# / Total)

21.25%

(17 / 80)

20%

(16 / 80)

Proportion of tiles with recruitment (# / Total)

2630Total number of recruits

Stegastes Removed

Stegastes Present

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

PRESENT REMOVED ABSENT

Pro

po

rtio

n o

f T

ota

l R

ecr

uit

me

nt

UNID

Porites

Pocillopora

Montipora

Acropora

0.32

(8 / 26)

0.15

(4 / 26)

0.10

(3 / 30)

UNID

0.04

(2 / 26)

0.32

(8 / 26)

0

(0 / 26)

0.32

(8 / 26)

ABSENT

0.08

(2 / 26)

0.23

(6 / 26)

0.15

(4 / 26)

0.39

(10 / 26)

REMOVED

0.03

(1 / 30)

0.13

(4 / 30)

0.26

(8 / 30)

0.46

(14 / 30)

PRESENT

PoritesPocilloporaMontiporaAcropora

Indirect Effects Alter Coral Community...

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