Did you know corals can get diseases?

04.02.2025

In order to understand the health of Fregate’s coral reefs, the Conservation and Sustainability Intern, Chloe Mclanachan, created and planned a research project looking at the presence of disease within coral colonies. Coral reefs are fragile ecosystems at threat from issues such as bleaching, pollution, overfishing and disease. Diseases can pose significant challenges for reefs and, if left unchecked, have the potential to destroy a coral reef entirely.

Monitoring coral reef disease prevalence on Fregate’s reefs will help the conservation team understand how healthy the area is and if there are colonies that need to be more closely monitored. Chloe set up a long-term monitoring project consisting of two sites: one looking at coral health on granitic rock and the other on a carbonate reef slope. Together with the conservation team, she set up three transects (shallow, medium, and deep) to compare data from varying depths and determine if certain depths are more susceptible to disease.

To understand disease prevalence, an inventory of every single coral colony within each transect was conducted by photographing them next to a ruler. Each photo was then analyzed to identify coral colonies showing signs of disease. Identification tools, including The Coral Disease Identification Key (NOAA) and the Underwater Cards for Assessing Coral Health on Indo-Pacific Reefs (University of Queensland), were used to determine the type of disease affecting the coral.

Data collection will take place twice a year in March/April/May and again in September/October/November. This schedule allows the team to assess whether disease prevalence varies with changes in water temperature. Monitoring coral reef disease over a longer period provides an overview of coral reef health as it fluctuates due to factors such as water temperature, pollution levels, and fishing intensity.