Identification of Crustose Coralline Algae Species in Florida and Their Ability to Induce Larval Settlement of Caribbean Corals

Author

Danielle Macias, Nova Southeastern UniversityFollow

Defense Date

7-31-2025

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Joana Figueiredo

Second Advisor

Aurora Giorgi

Third Advisor

Timothy Swain

Keywords

CCA, genetics, metamorphosis, settlement cue, sexual propagation

Abstract

Crustose coralline algae (CCA) are a diverse, globally spread and yet poorly studied group of benthic organisms. They act as settlement cues for coral larvae, but this interaction is often species-specific, as CCA species can be either inducers or inhibitors to larval settlement and metamorphosis. Despite this importance, information on Caribbean CCA distribution, diversity, and impact on coral species is limited due to the difficulty in identifying them. In the present study, CCA samples were collected from seven different reef sites in the southeastern region of Florida’s Coral Reef and genetically identified using molecular analyses. Some of the samples collected ended up not being CCA, but instead Peyssonneliales, thought to be as inhibitors of coral settlement and/or overgrow corals, and thus killing them. Seven different genera of CCA were found, and of these, three species, Lithophyllum sp., Lithothamnion sp., and Porolithon sp., were tested for their effect on larval settlement and metamorphosis of Montastraea cavernosa, Orbicella faveolata, Pseudodiploria strigosa, P. clivosa, and Colpophyllia natans. In these settlement trials, coral larvae were provided with a settlement tile which was either pre-conditioned or not conditioned to determine if biofilm induced coral settlement and metamorphosis. Each CCA species was tested with a conditioned and non-conditioned tile to determine if the CCA would act synergistically with biofilm for settlement, or if the CCA by itself was enough of a cue to induce settlement. None of the three CCA species tested enhanced nor inhibited larval settlement and metamorphosis in the coral species studied. However, tile pre-conditioning for M. cavernosa, P. strigosa, and P. clivosa caused a significant increase in settlement and metamorphosis. The lack of settlement-inducing CCA may partially explain the decline in coral cover and coral recruitment in the southeastern region of the Florida’s Coral Reef and the need for better understanding of larval settlement and metamorphosis cues of Caribbean coral species.

NSUWorks Citation

Danielle Macias. 2025. Identification of Crustose Coralline Algae Species in Florida and Their Ability to Induce Larval Settlement of Caribbean Corals. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (217)
https://nsuworks.nova.edu/hcas_etd_all/217.