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.

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.

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

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. 3b. False UB light enhanced to show the context of the site.

CieLab:

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

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?

Method:

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 )

Materials:

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.

Variables:

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

Findings:

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

GPS

Time

Date

Tempe C

Source

Photo #

Pic Area

Observer

18:45

27.2

DSCI12795

-48

-33

Knapp

18:45

27.2

DSCI12795