Download - Response of herbivore functional groups to multiple disturbances in Moorea, French Polynesia
Xueying (Shirley) Han, R Schmitt, S Holbrook,
A Brooks, T Adam
University of California, Santa Barbara
7 August 2013
ESA
Response of herbivore functional groups to
multiple disturbances in Moorea, French Polynesia
BackgroundDisturbances
Ocean acidification Disease outbreaks Large stormsGlobal warming
HerbivoresHerbivorous fishes and sea urchinsControls macroalgaeCrucial to coral reef systems
Moorea, French Polynesia
2008-2009
Acanthaster planci:Crown-of-thorns starfish
(COTS) outbreak
February 2010
Cyclone Oli
Consequences
Decrease in fore reef coral cover from ~40% to ~3%Decline in corallivores and coral dwellersIncrease in herbivores
Adam et al. (in prep)
Study Site: MooreaHabitats (3): fringing, backreef, and fore reef
Sites (6): LTER1-6
Total: 18 sites
Annual fish surveys: 2006-2012
BrowsersDetritivoresExcavatorsFarmersGrazer/detritivoresScrapers
Herbivore Functional Groups
Browser—consumes standing macroalgae(e.g. Naso lituratus)
Herbivore Functional Groups
Browser—consumes standing macroalgae(e.g. Naso lituratus)
Detritivore—consumes detritus(e.g. Ctenochaetus striatus)
Herbivore Functional Groups
Browser—consumes standing macroalgae(e.g. Naso lituratus)
Detritivore—consumes detritus(e.g. Ctenochaetus striatus)
Excavator—consumes epilithic algal turf and removes large amounts of the calcium carbonate substrata(e.g. Chlorurus sordidus)
Herbivore Functional Groups
Farmer—site-attached, territorial species that maintain algal farms(e.g. Stegastes nigricans)
Herbivore Functional Groups
Farmer—site-attached, territorial species that maintain algal farms(e.g. Stegastes nigricans)
Grazer/detritivore—feeds on epilithic algal turf without scraping/excavating the substratum(e.g. Acanthurus nigrofuscus)
Herbivore Functional Groups
Farmer—site-attached, territorial species that maintain algal farms(e.g. Stegastes nigricans)
Grazer/detritivore—feeds on epilithic algal turf without scraping/excavating the substratum(e.g. Acanthurus nigrofuscus)
Scraper—consume epilithic algal turf and small portions of the reef substratum(e.g. Scarus psittacus)
Questions
1. How did functional groups respond on an island-wide scale?
2. Are there differences in the functional community assemblage among the three habitats?1. Did these habitats respond similarly
to the disturbance?
3. Are responses related to the initial biomass of a species?
Island-wide response of functional groups
Functional group
Scraper
Excavator
DetritivoreGrazer/detritivore
Browser
Farmer
Magnitude of change
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Functional groups responded differently in both direction and magnitude.
Island-wide response of functional groups
Pre-disturbance biomass (g/m2)
0 2 4 6
Post-disturbance biom
ass (g/m2 )
0
1
2
3
4
5
6
7
ScraperExcavator
Detritivore
BrowserFarmer
Grazer/detritivore
Functional group response is not related to pre-disturbance biomass.
Functional community assemblages among habitats
1. Habitats have different functional assemblages.2. Despite difference, the response among habitats was the same
—increased scrapers.
Are responses related to the initial biomass of a species?
Forereef
Species
Ctenochaetus striatus
Acanthurus nigrofuscus
Centropyge flavissima
Chlorurus sordidus
Zebrasoma scopas
Naso lituratusCtenochaetus flavicauda
Centropyge bispinosa
Acanthurus nigricans
Centropyge loricula
Stegastes fasciolatus
Acanthurus pyroferus
Scarus oviceps
Scarus psittacus
Ctenochaetus binotatus
Centropyge heraldi
Naso unicornis
Naso annulatus
Acanthurus nigricauda
Acanthurus olivaceus
Scarus forsteni
Zebrasoma veliferum
Scarus altipinnis
Cha
nge
in Bio
ma
ss
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
**
**
* *
*
*
Response is not related to a species’ pre-disturbance biomass.
BrowserDetritivoreExcavatorFarmerGrazer/detritivoreScraper
Summary1. How did functional groups respond on an island-
wide scale?
Herbivore functional groups responded differentlyDirection and magnitude of response was not related to the pre-disturbance biomass of a functional group
Summary1. How did functional groups respond on an island-
wide scale?
Herbivore functional groups responded differentlyDirection and magnitude of response was not related to the pre-disturbance biomass of a functional group
2. Are there differences in the functional community assemblage among the three habitats?1. Did these habitats respond similarly to the
disturbance?Characteristically different functional assemblages among habitatsAll habitats moved towards a community with increased scrapers
Summary1. How did functional groups respond on an island-
wide scale?
Herbivore functional groups responded differentlyDirection and magnitude of response was not related to the pre-disturbance biomass of a functional group
2. Are there differences in the functional community assemblage among the three habitats?1. Did these habitats respond similarly to the
disturbance?Characteristically different functional assemblages among habitatsAll habitats moved towards a community with increased scrapers3. Are responses related to the initial biomass of a species?Differences in post-disturbance response are not related to the initial biomass of a species
Outline Background/introduction Recent dynamics in Moorea, French Polynesia Study site Herbivore functional groups Research questions
How did functional groups respond on an island-wide scale?
Are there differences in the functional community assemblage among the three habitats?
Did these habitats respond similarly to the disturbance?
Are responses related to the initial biomass of a species?