Project completed by Hana Kaloudis

Research Questions / Objectives

This project investigated the ecological relationship between reef fish diversity and teh prevalence of White Syndrome, a tissue-loss disease affecting corals on O’ahu’s reefs. Coral reefs support ~25% of all marine life, and fish play mixed roles: they promote reef health through herbivory and nutrient cycling but may also vector pathogens via feeding wounds and contact. Coral disease studies in Hawai’i remain underresearched, particularly concerning White Syndrome and fish interactions. The primary research questions were: 

1. What is the correlation between fish diversity and the prevalence of White Syndrome in transects with comparable coral coverage?
2. Does fish diversity correlate negatively with disease prevalence, suggesting a protective effect?
3. How do patterns differ between sites with distinct management histories and coral assemblages (Horseshoe Reef vs. Turtle Canyons)?

Methods         

Surveys were conducted at two sites: Horseshoe Reef in Kewalo Basin and Turtle Canyons  in Maunalua Bay. At each site, four transects were established 

• Coral Surveys: 30 × 2 m belt transects, recording colony counts by genus (Pocillopora, Porites, Montipora, Leptastrea, Pavona, Fungia) and identifying White Syndrome instances. Orthomosaics were used when in-water counts were difficult.
• Fish Surveys:  30 × 5 m transects, conducted after a 5-minutes settling period. Buddy teams tallied indicator species (e,g., butterflyfish, tangs, surgeonfish, parrotfish) based on trophic role and ecological importance. 
• Data analyses: Results were standardised for coral cover, fish diversity was calculated with Shannon Index, and correlation with disease prevalence were tested statistically (α = 0.05). 

Results                                                                                                                           

Surveys revealed contrasting relationships between fish diversity and disease prevalence across sites, supporting the hypothesis at one location but not the other.

• Horseshoe Reef: A significant negative correlation was found between fish diversity and prevalence of White Syndrome (p = 0.0028), supporting the hypothesis that higher fish diversity mitigates disease risk.
• Turtle Canyons: No correlation was detected (p = 0.329), suggesting site-specific dynamics or survey confounding factors.
• These results align with existing literature showing mixed outcomes in fish-coral interactions: in some contexts, fish communities reduce disease, while in others, they may spread pathogens

Significance                                                                                                                        

This study provides the first dataset from O’ahu explicitly linking reef fish diversity with White Syndrome prevalence, filling a major knowledge gap in Hawaiian coral disease ecology. The findings indicate that diverse fish assemblages may help buffer coral disease risk, but effects are site-dependent. These insights can inform fisheries management, reef restoration, and integrated coral health monitoring.