Further Research

The graphs produced by this website are neither exhaustive nor exclusive. There are many other types of graphs that can be produced and we encourage you to explore different options and do further research comparing reef health. The following graphs are examples of graphs you can create using your data with Microsoft Excel.

Comparing reef health before, during and after a bleaching event 

A graph of the Heron Reef during and after a bleaching event

Repeated measurements of specific colonies

The left graph shows Colour Chart measurements from 20 marked corals on Heron Island, Australia. Corals that showed signs of bleaching in March 2002 had significantly lighter colours than corals that were not affected. From May onwards, there was no significant difference between the two groups. In early September, a rainstorm coincided with a low tide and resulted in bleaching of both, previously healthy and bleached colonies.

 Recovered reefs

'Fingerprinting' different reefs

 The graph on the right shows the distribution of the colours of 100 randomly selected corals after the 2002 mass bleaching event on the Great Barrier Reef, Australia. They provide a 'fingerprint' for a reef at a certain point in time, with the distribution reflecting the condition of the reef. This graph compares three reefs with each other.

Comparing coral colour score values and coral types


A graph of average colour score by coral type

The graph on the left shows the average colour score for each type of coral on a particular reef. As you can see, branching and plate corals had higher colour scores, and are therefore considered healthier coral types on this reef than boulder and soft corals.

A frequency graph of colour score by coral type

The graph on the right takes this one step further and lets you know how many colonies of each coral type fell under each colour score. As you can see, the only type to have a colour score of 2 was soft coral, and it appears that three colonies were surveyed having this score. Most colonies surveyed had a colour score of 4, which means this reef is fairly healthy.

Research projects for the next time you collect data

The reaction of corals to various stressors may be influenced by coral type, species and/or depth and location. To address these potential differences you can:

  • Select multiple types (i.e. equal ratios of branching, boulder, plate and/or soft corals) to provide a more detailed picture of reef health.
  • Select particular species for assessment and comparison within set areas.
  • Conduct a depth comparison at, say, 3, 6 & 9 metres. Remember, a torch must be used below 5 metres (15 feet) to illuminate the Chart and corals.
  • Natural variation in coral colour occurs as a result of environmental conditions. For example, elevated temperature and intense rainfall can reduce a coral’s symbiont concentration, thereby affecting its colour. Check what the weather conditions were like at your location before you arrived. State any unusual weather patterns experienced at your location recently and what impact you think they had on the reef.

We would love to receive feedback and reports from your findings. Please email us at info@coralwatch.org.

We continually need more data to measure trends and improve our understanding and capacity to conserve reefs. Please remember to enter all of your real data onto this website. Alternatively, you can mail your raw data sheets or email your completed spreadsheets to us and we’ll upload them for you. Please do not enter any of the virtual data, i.e. from the Virtual Reef, Virtual Lab or Virtual Transect, onto the website. Thank you so much for your continued support of CoralWatch and your enthusiasm for healthy reefs!