Coral bleaching

This rapid assessment field method can be used to quantify coral bleaching for different genera of hard corals.

In this rapid assessment field method, the sample unit is a collection of quadrats observed for coral bleaching on a single dive/snorkel. The method is described in detail here.

First, observers choose a consistent quadrat size (typically 1 to 2m2) to use on the survey. During a survey, an observer records information from a set of quadrats, typically ~15-20 quadrats. Within a quadrat, an observer first counts the number of coral colonies for each hard coral genus and classifies each colony within 7 categories of bleaching severity: normal, pale, 0-20% bleached, 20-50% bleaching, 50-80% bleaching 80-100% bleached, recently dead. After recording the coral colonies, the observer then visually estimates the cover of three main benthic groups wiithin the quadrat: hard coral, macroalgae, and soft coral. Then, the observer swims a set distance (e.g., 10 fin kicks) to begin the next quadrat. 

In MERMAID, observations from the surveys are recorded in 2 sections. The 'colonies bleached' sections records the total total number of colonies in each bleaching category for each genus. The 'percent cover' section records the % cover of hard coral, macroalgae, and soft coral for each quadrat. 


Use the ‘tab’ keys to move across the colonies bleached and percent cover columns. At the end of the row, press 'Enter' to create a blank row to add the next complexity observation. If the same bleaching or percent cover is observed at the next interval, press the ‘Tab’ key at the end of the row to duplicate.