Fluorescent Photos to Measure Reef Viability (2)

The condition of the Caribbean reefs has been observed for decades thanks to dedicated marine biologists and experienced scuba divers. I wanted to observe, document, and inform others about the disease which is unseen and under-appreciated by most during this time of our human Covid epidemic. The disease is called Stony Coral Tissue Loss Disease (SCTLD). See previous post Death in Paradise. Also see Marine Life Could Be Like This In SWFL.

I believed that for the observation of reef polyp viability an adjunct to visible light one should consider a non-invasive test using reef fluorescence observation to determine SCTLD extent and its progress. The green fluorescent proteins (GFP) of many living reef polyps can fluoresce in response to exposure to specific light wavelengths.1 They exhibit variations in fluorescence in terms of wavelength (color) and intensity (brightness).2 We will call this reef temperature. Non-viable reef polyps and plant forms appear to differ significantly in fluorescent wavelength and dimmer luminance or appear black.7

Examples of observations and photographs that I made made between December 12 and December 14, 2012 in the Caribbean Site #16. The light sources were: White light from Nikonos S1B flash and Blue light (Ultra Blue UB) source from SeaLife FluroDive gear which generates Ultra Blue (UB) light.3,4 No GPS or location descriptions are provided. Imbedded in the images are CieLab* notations.

Fig. 1a shows an area of coral with damage probably a result of SCTLD. Fig. 1b shows a similar area with UB lighting where the damage has lost the polyp layer and the accompanying protein of those polyps is missing. Since the polyps are the source of the fluorescence when dead they do not reflect.

Fig. 1a. White light
Fig 1b. UB light

This small area shown in Figs. 2a and b may show the advancement of the process where mottled dark areas without fluorescence are present. Green areas circled in amber are not yet afflicted. The circled blue areas show disease in progress and black areas are dead. The different spectrum shows compromised surface. The amber circled areas were color sampled via Photoshop. The blue area sampled is smaller than the green area. The blue area L.a.b. is 54,-48,-33. The green area L.A.B. is 15,20,26. This is a remarkable difference in light values.

Fig 2a. White light
Fig. 2b. UB light

These color extracted areas in Figs. 2ac and 2d permit visualization of the percentage of healthy and compromised polyps.

Fig. 2c. UB light green extract
Fig. 2d. UB blue extract

The Fig. 3 series of photos show another reef area.

Figs. 3a through 3d show a different variety of stony coral which is not suffering any apparent SCTLD but is surrounded by areas that are dead coral overgrown with algae.

Fig. 3a. UB light unaltered.
Fig. 3b. False UB light enhanced to show the context of the site.
Fig. 3c. UB and white combined.
Fig. 3d. UB light alone with selected CieL.a.b. readings in amber areas.


CieLab5 is a photometric method of describing a three dimensional color space. It is more comprehensive than RGB, Panatone, CMYK or HSB.

Three dimensional graphic representation of CieLab color space. From Prospector

This appears to be a useful method for assessing reef viability. Here is what I propose:

The Important question (null-hypothesis):

Why aren’t reefs all the same color temperature?


Expose a fixed area to white light and the same area with the UB light and photograph each using an appropriate filter. Similarily, photograph variations in coral species and other variables and photograph them. Compare the photos using Photoshop to interpret the light of the ultra blue photograph. Record the data of light hue, chroma, luminance (CieLab. color space )


  • UW camera with filter (SeaLife)
  • UW fluorescent blue light lamps aimed for even distribution of light
  • Plastic pipe square frame 1 meter X 1.5 M with fixed 1.5 M legs to support camera
  • Software (Photoshop and Excel)

Exposure technique:

Establish a standard normal site. Select an ideal healthy reef area and use this as a basis. Photograph it using the method listed above with the camera at the center of a standard square. Mark GPS location (Drop a weighted line from dive boat). Include other very pertinent information like temperature, current flow and other variables as noted below.

Select a typical affected reef test site and use this as a basis. Photograph it using the method listed above with the camera at the center of the square. Mark GPS location (Drop a weighted line from dive boat). Repeat additional test sites.

Data collection technique using Photoshop for each photo:

Data is collected in a selected photo area as numeric readings in CieL.a.b.. Include a standard sample (B&W and Color). Collect CieL.a.b. data in photo as a fraction or total picture.

Number of sites

The number of sites depends on the area of interest and existing information. Examples include proximity or remoteness to areas of traffic or resort, city, sewage effluent, runoff’s, windward, and leeward sides of island . Ten to one hundred sites are conceivable.


Seasons, lunar cycles, temperature, months, storms, rise in water level, toxic products, population growth, recreational usage, associated life forms and structures.


Findings could be collected in an Epicollect5 data base in a standard fashion6. This would be available to the public for observation or assessment and downloadable in a cd file. The file could be manipulated in Excel at the discretion of interested parties. At this time I have included a simple table for data presentation.

Num.Subject GPSTimeDateTempe CSourcePhoto #Pic AreaLa.b.Observer
Typical but incomplete data file structure UB=Ultra Blue, W=White sc=stony coral, ag=algae

Data manipulation in Excel:

Statistical analysis of findings by comparing normal to test site data will be done when an adequate number of observations are gathered. This could imply what is happening to the reef by comparing measures between and among species and locations. Measurement may make possible knowledge based judgements.


Given this limited data base all conclusions are still speculative. In image Fig. 2b area G exhibits a Luminance value 54%, 48% green value, and a 33% blue value. In image 2d area B L is 15%, 20% green value, 24% red value. This suggests that viable polyps in this image are 34% more luminescent, 28% more green and 57% more blue than their counter parts in the blue areas. In image Fig 3d area G is very polyp viable and area R appears to have little or no polyp viability. Areas G in both Fig 2b and 3d are remarkable similar. They may have similar GFP. Better controls and more numerous observations may provide improved accuracy.8


UW Fluorophotography seems to have the ability to distinguish viable from absent, unhealthy or dead coral polyps.


This pilot study suggests that the null-hypothesis may be refuted. The answers to some important questions can be implied from the data. All of the reefs are not the same color temperature. This may point to answers for these questions. Reefs do vary in terms of variables mentioned above. Reef color values indicate viability across all species. Color does indicate the progress of SCTLD. At a larger level; there is a general trend in reef viability, measures taken can show an improvement, stabilization, or degradation the reef in size, viability, or level of SCTLD. This answers can be substantiated in a more controlled test with measures mentioned in the statement of method noted below.

This trial test suggests that there may be additional documentable methods for judging the reef system. These important questions need to be addressed. Should intervention of reef life be done? How do you know if interventions are effective?

These measures should be initiated:

  • Expanded use of communal data base
  • Expanded data collection to multiple data collectors.
  • Improved method;
    • Photo fluoro-microscopy of sectons of coral polyp growth
    • Differentiation of CieLab images of coral species
    • Inclusion of a photo standard B&W and Color into photos
    • Stabilization of position of UW camera
  • Further infrastructure development;
    • Capacity of shores and islands to continue development
    • Sustainability measures
      • Water supply, sewage treatment, electricity supply, 
  • What is the expectation for the future?
  • Can information of effectiveness of measures be transferred to other locations?

The motivations are critical to the stakeholders of the entire Caribbean:

  • Should further research be done? 
  • Will reef conditions effect resort business?
  • Should reef recreation and fishing business models be modified?

My hope is to continue to help in the management of this problem and that you, too, are willing to help. Please let me know of your interest and comments. Please look for the next post in this series to see plans for further work in marine biology.


  1. Applying new methods to diagnose coral disease.
  2. Fluorescence-Based Classification of Caribbean Coral Reef Organisms and Substrates David G.
  3. Fluorphotorgaphy Zawada , Charles H. Mazel
  4. SeaLife
  5. Three dimensional representation of CieLab space
  6. Epicollect5
  7. Fluorphotorgaphy
  8. Fluorescence-Based Classification of Caribbean Coral Reef Organisms and Substrates David G. Zawada , Charles H. Mazel

Important supporting references:

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#fluorophotography #green fluorescent protein #CieLab #color temperature #research #marine biology #Caribbean

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