Impact of Herbivory, Structural Complexity, and Sediment on Caribbean Coral Reefs

Authors

Alain DuranFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Ligia Collado-Vides

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Deron E. Burkepile

Second Advisor's Committee Title

Co-advisor

Third Advisor's Name

Kevin Boswell

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Alastair R Harborne

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Jennifer Rehage

Fifth Advisor's Committee Title

Committee member

Keywords

surgeonfishes, parrotfishes, macroalgal succession, coral recruitment, marine ecology

Date of Defense

3-30-2018

Abstract

The resilience of coral reefs depends, among others, upon local physical and biological characteristics. This dissertation focused on how herbivory, structural complexity, and sedimentation can impact the structure, function, and, ultimately, resilience of Caribbean coral reefs. We filled an important knowledge gap related to trophic niche and ecological roles of surgeonfishes (A. coeruleus and A. tractus), two of the most important herbivorous fishes in the Caribbean. We showed that both species feed primarily on turf algae preventing further progression of algal succession while A. tractus may also help reduce macroalgal abundance by targeting common macroalgal species such as Dictyota spp. We used a factorial experiment to analyze the interactive effects of herbivory (exclosure vs. open plots) and reef structural complexity (vertical vs. horizontal substrate orientation), on the development of benthic communities. We found that vertical substrates were quickly dominated by crustose algae regardless of herbivory treatment while succession of horizontal substrates was determined by herbivory. Our results suggest that at small scale, reef complexity is a major factor determining algal community structure. We investigated why, despite high levels of herbivory, coral cover in South Florida has failed to recover. We surveyed benthic composition, grazing and abiotic characteristics along six spur and groove reefs in the Florida Keys. Using boosted regression tree analyses, we found that sediment abundance was the best predictor of both juvenile and adult corals, which could explain the failure of coral recovery. We studied spatial and temporal changes of reef communities of reefs in Havana, Cuba where global and local stressors have affected coral communities while overfishing and nutrient enrichment has led to low herbivory levels. Our surveys revealed a region-wide high abundance of algae (~60%) as a consequence of heavy overfishing with likely negative consequences on coral recovery. In summary, my dissertation showed context-depend effects of herbivory, structural complexity, and sediment on Caribbean coral reefs. While reduction of herbivory can often suppress coral recovery, on coral reefs with robust herbivore populations, physical factors such as structural complexity and sediment may still limit coral recovery and fundamentally impact reef resilience.

Identifier

FIDC006531

Recommended Citation

Duran, Alain, "Impact of Herbivory, Structural Complexity, and Sediment on Caribbean Coral Reefs" (2018). FIU Electronic Theses and Dissertations. 3708.
https://digitalcommons.fiu.edu/etd/3708