Response of herbivore functional groups to multiple

Report
Xueying (Shirley) Han, R Schmitt, S Holbrook,
A Brooks, T Adam
University of California, Santa Barbara
[email protected]
7 August 2013
ESA
Disturbances
 Ocean acidification
 Disease outbreaks
 Large storms
Global warming
Herbivores
Herbivorous fishes and sea urchins
Controls macroalgae
Crucial to coral reef systems
2008-2009
February 2010
Acanthaster planci:
Crown-of-thorns starfish
(COTS) outbreak
Cyclone Oli
Decrease in fore reef coral cover
from ~40% to ~3%
Decline in corallivores and coral
dwellers
Increase in herbivores
Adam et al. (in prep)
Habitats (3): fringing,
backreef, and fore reef
Sites (6): LTER1-6
Total: 18 sites
Annual fish surveys:
2006-2012
Browsers
Detritivores
Excavators
Farmers
Grazer/detritivores
Scrapers
Browser—consumes standing macroalgae
(e.g. Naso lituratus)
Browser—consumes standing macroalgae
(e.g. Naso lituratus)
Detritivore—consumes detritus
(e.g. Ctenochaetus striatus)
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)
Farmer—site-attached, territorial species
that maintain algal farms
(e.g. Stegastes nigricans)
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)
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)
1.
How did functional groups respond on an islandwide 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?
1.0
Magnitude of change
0.8
0.6
0.4
0.2
0.0
-0.2
er
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-0.4
Functional group
Functional groups responded differently in both direction and magnitude.
Post-disturbance biomass (g/m 2)
7
Detritivore
6
5
Scraper
Excavator
Grazer/detritivore
4
3
2
1
Browser
Farmer
0
0
2
4
6
Pre-disturbance biomass (g/m 2)
Functional group response is not related to pre-disturbance biomass.
1. Habitats have different functional assemblages.
2. Despite difference, the response among habitats was the same—increased
scrapers.
Forereef
2.5
*
2.0
*
Change in Biomass
Browser
Detritivore
Excavator
Farmer
Grazer/detritivore
Scraper
1.5
1.0
*
0.5
*
*
*
0.0
-0.5
*
-1.0
*
-1.5
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Species
Response is not related to a species’ pre-disturbance biomass.
1.
How did functional groups respond on an island-wide
scale?
Herbivore functional groups responded differently
Direction and magnitude of response was not related to the
pre-disturbance biomass of a functional group
1.
How did functional groups respond on an island-wide
scale?
Herbivore functional groups responded differently
Direction 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 habitats
All habitats moved towards a community with increased scrapers
1.
How did functional groups respond on an island-wide
scale?
Herbivore functional groups responded differently
Direction 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 habitats
All habitats moved towards a community with increased scrapers
3.
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
Thank you!
Questions?
[email protected]
@xueyinghan
 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?

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