Project completed by Isabella Weigle
Research Questions / Objectives
This project investigated the dynamics of White Syndrome (WS) lesion expansion across coral colonies in Maunalua Bay, Oʻahu. While WS is a widespread and damaging tissue-loss disease, little is known about how lesion progression rates vary across species or lesion sizes in Hawaiian reefs. The primary research questions were:
- How does lesion expansion rate vary with initial lesion size and host species identity (Montipora vs. Porites)?
- What are the average rates of tissue loss across short-term (7- and 14-day) and long-term (6-month) intervals?
- Does lesion size change consistently over time?
- Can photogrammetric and photographic methods provide standardized, replicable protocols for lesion monitoring across reefs?
Methods
The study was conducted in permanent 5 × 5 m reef plots in Maunalua Bay, Oʻahu, where colonies of Montipora and Porites with active White Syndrome lesions were tagged for repeated monitoring. The methodology followed a standardized sequence:
- Colony selection: Lesion-bearing colonies were identified, tagged in situ, and recorded with species identity and initial lesion size.
- Image acquisition: Tagged colonies were photographed at Day 1, Day 7, Day 14, and six months using high-resolution DiveVolk cameras, with scale references included for calibration.
- Lesion measurement: ImageJ software was used to trace lesion perimeters and calculate 2D area, and 3D photogrammetry was employed to reconstruct colony surfaces and quantify lesion growth across rugose topography. Lesion expansion was recorded both linearly (cm/day) and by areal tissue loss (cm²/day).
- Data analysis: Linear mixed-effects models were implemented in R to assess the effects of species identity, initial lesion size, and time point on lesion progression, with colony identity treated as a random effect to account for repeated measures.
Results
Surveys revealed consistent lesion progression over both short- and long-term intervals.
- Overall growth: Lesions expanded at an average of ~2.05 cm²/day (SE: 0.81, p = 0.0003).
- Species differences: Montipora lesions averaged ~3.95 cm²/day, while Porites averaged ~1.42 cm²/day, though differences were not statistically significant (p = 0.12).
Significance
This project establishes one of the first quantified baselines of WS lesion expansion in Hawaiian corals, addressing a gap as most prior studies emphasized prevalence rather than lesion dynamics. It underscores the importance of host identity in disease outcomes. The use of 3D photogrammetry alongside ImageJ establishes replicable protocols for scientists and community members. These findings contribute to a growing body of literature showing that Vibrio-associated tissue loss diseases can progress rapidly, especially under stress, and highlights the urgent need for early detection and intervention
