Response of herbivore functional groups to multiple disturbances in Moorea, French Polynesia

1. 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 xhan@lifesci.ucsb.edu 7 August 2013 ESA

2. Background • Disturbances • Ocean acidification • Disease outbreaks • Large storms • Global warming • Herbivores • Herbivorous fishes and sea urchins • Controls macroalgae • Crucial to coral reef systems

3. Moorea, French Polynesia 2008-2009 February 2010 Acanthasterplanci: Crown-of-thorns starfish (COTS) outbreak Cyclone Oli

4. Consequences • Decrease in fore reef coral cover from ~40% to ~3% • Decline in corallivores and coral dwellers • Increase in herbivores Adam et al. (in prep)

5. Study Site: Moorea 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

6. Herbivore Functional Groups Browser—consumes standing macroalgae (e.g. Nasolituratus)

7. Herbivore Functional Groups Browser—consumes standing macroalgae (e.g. Nasolituratus) Detritivore—consumes detritus (e.g. Ctenochaetusstriatus)

8. Herbivore Functional Groups Browser—consumes standing macroalgae (e.g. Nasolituratus) Detritivore—consumes detritus (e.g. Ctenochaetusstriatus) Excavator—consumes epilithic algal turf and removes large amounts of the calcium carbonate substrata (e.g. Chlorurussordidus)

9. Herbivore Functional Groups Farmer—site-attached, territorial species that maintain algal farms (e.g. Stegastesnigricans)

10. Herbivore Functional Groups Farmer—site-attached, territorial species that maintain algal farms (e.g. Stegastesnigricans) Grazer/detritivore—feeds on epilithic algal turf without scraping/excavating the substratum (e.g. Acanthurusnigrofuscus)

11. Herbivore Functional Groups Farmer—site-attached, territorial species that maintain algal farms (e.g. Stegastesnigricans) Grazer/detritivore—feeds on epilithic algal turf without scraping/excavating the substratum (e.g. Acanthurusnigrofuscus) Scraper—consume epilithic algal turf and small portions of the reef substratum (e.g. Scaruspsittacus)

12. 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?

13. Island-wide response of functional groups Functional groups responded differently in both direction and magnitude.

14. Island-wide response of functional groups Functional group response is not related to pre-disturbance biomass.

15. Functional community assemblages among habitats Habitats have different functional assemblages. Despite difference, the response among habitats was the same—increased scrapers.

16. Are responses related to the initial biomass of a species? Browser Detritivore Excavator Farmer Grazer/detritivore Scraper Response is not related to a species’ pre-disturbance biomass.

17. Summary 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

18. Summary 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 • Are there differences in the functional community assemblage among the three habitats? • Did these habitats respond similarly to the disturbance? • Characteristically different functional assemblages among habitats • All habitats moved towards a community with increased scrapers

19. Summary 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 • Are there differences in the functional community assemblage among the three habitats? • Did these habitats respond similarly to the disturbance? • Characteristically different functional assemblages among habitats • All habitats moved towards a community with increased scrapers 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

20. Thank you! Questions? xhan@lifesci.ucsb.edu @xueyinghan

21. 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?