Fluorescent Photography Highlights Coral Health Issues

Introduction

This section presents a structured account of observations made in the reef system surrounding Roatan, Honduras. This is not unique to this location but the conditions are consistent with other findings in the reef systems of the Gulf. These findings and identifications are based on personal experience and the efforts of amateur naturalists. These observations extend a continuing investigation into coral reef health, previously initiated in the post titled “Death in Paradise.” See past posts. This is presented is made to support my application to the Water School at Florida Gulf Coast University to study for a Master’s in Environmental Sciences. The goal is to learn more about coral reefs, coal polyps, and polyp disease.

These observations are findings revealed by white light flash photography during the day and ultra blue illumination lighting with amber filtration to show fluorescence at night. It was not possible to superimpose photos of identical structures due to instability caused by rough sea conditions.  

IMAGES WITH FLUORESCENT LIGHT

Figure 1: Fluorescent Green Goniopora Coral

Photographed using an ultra-blue light source and an amber filter, this image depicts a fluorescent green Goniopora coral, also known as the flowerpot coral. Under white light, these corals appear dull brown, but under blue or UV light, their fluorescent pigments—produced by dinoflagellate algae within the polyp—create a vivid green glow. This species is a Large Polyp Stony (LPS) coral, notable for long, fleshy polyps resembling a bouquet of flowers. The coral may belong to either the Goniopora or Alveopora genus, which can be differentiated by tentacle count—Goniopora polyps have 24 tentacles, while Alveopora have 12. 

A vibrant underwater scene showcasing colorful coral formations illuminated by blue and green light.
Figure 1. Photo with ultra blue light source and amber filter on camera

Figure 2: Tubastraea faulkneri (Orange Cup Coral)

This image, also captured with ultra blue lighting and an amber filter, shows a coral likely to be Tubastraea faulkneri, the orange cup coral. Typically orange, this species may display green or yellow variations under specific lighting. Tubastraea faulkneri is a non-reef building LPS coral, often inhabiting cryptic environments such as caves, overhangs, and shipwrecks. Notably, it is a zooxanthellate carnivore, lacking symbiotic algae and feeding by extending its polyps at night to capture plankton. Its distribution spans the Atlantic Ocean and Caribbean Sea with origins in the Indo-Pacific.

Close-up view of a vibrant coral formation with green and blue hues, surrounded by underwater vegetation.
Figure 2. Photo with ultra blue light source and amber filter on camera

Figure 3. Montastraea cavernosa (Great Star Coral)

This photograph features a coral with a bright green base and purple-rimmed polyps or tips, possibly a Neon Green Cyphastrea, Montastraea cavernosa (Great Star Coral), Goniopora, or Fimbriaphyllia (Frogspawn/Hammer coral).

Close-up of vibrant green coral polyps with a dark background, showcasing intricate textures and shapes.
Figure 3: Neon Green Cyphastrea or Similar Species

Figure 4.

An image taken with blue light and an amber filter shows a central region of dead coral polyps highlighting loss within the colony.

Close-up view of a vibrant green coral with glowing features, showing intricate patterns and textures against a dark background.
Figure 4: Central Area of Dead Coral Polyps

Figure 5: Montipora Coral (“Shamrock Monti” or “Rainbow Montipora”)

This photo reveals a Montipora coral, recognized for vibrant green polyps on a purple or blue base under actinic lighting. As an SPS coral, it displays a bumpy, encrusting growth form and is valued by reef keepers for its resilience and fast growth. The coloration varies with lighting conditions, often intensifying under different spectrums.

Close-up of vibrant green and purple coral with intricate details, dated 2026 1.1.
Figure 5. Photo with ultra blue light source and amber filter on camera

Figures 6–8: Disease Progression in Montipora Coral

Figure 6 shows a Montipora coral under blue light. Figure 7, an enlargement, illustrates zones of normal tissue, dysfunction, and tissue loss, suggesting the possible progression of Stony Coral Tissue Loss Disease (SCTLD). Figure 8 highlights an encrusting Montipora structure glowing green under blue/UV light, with blue/purple areas indicating disease and tissue death.

Close-up view of vibrant green and purple coral formations under UV light, with a date overlay of '2026 1.19'.
Figure 6. Photo with ultra blue light source and amber filter on camera
An underwater image showing coral with zones labeled 'Tissue Loss Zone', 'Transition Zone', and 'Normal', illustrating coral health variations.
Figure 7. This enlargement of the Figure 6 image shows the possible progress of SCTLD on the surface of the coral reef. Indicated are the various zones of normal, dysfunctional and tissue loss zone.
Close-up view of a vibrant, textured coral surface illuminated with green and purple hues, showcasing intricate patterns and details underwater.
Figure 8. Photo with ultra blue light source and amber filter on camera

Figure 9: Surviving Fluorescent Polyp Coral

This image depicts a fluorescent polyp coral barely surviving amidst lifeless surfaces devoid of reflective polyps.

A close-up image of colorful coral under ultraviolet light, showcasing vibrant hues of blue and purple against a dark background.
Figure 9. Photo with ultra blue light source and amber filter on camera 

Figure 10: WWC Electric Daisy (Stylocoeniella armata)

This specimen is a small polyp stony (SPS) coral, forming a dense, textured mat and known to compete with other corals upon contact. (often called a “thorn coral”).

Close-up of a colorful coral with bright green and pink dotted patterns in an underwater setting.
Figure 10. Photo with ultra blue light source and amber filter on camera

Figure 11: Maze Brain or Worm Brain Coral

Likely a Platygyra or Favia species, these coral display neon green and purple fluorescence due to specialized proteins. It forms dome-shaped colonies with maze-like channels and can be semi-aggressive, extending sweeper tentacles at night. Nutrition is primarily derived from symbiotic algae.

Close-up of vibrant green coral with purple patterns under blue lighting, showcasing underwater marine life.
11. Photo with ultra blue light source and amber filter on camera Figure 

Figure 12: Encrusting Montipora or Cyphastrea

This image shows an encrusting coral, possibly Montipora or Cyphastrea, with green and purple fluorescence. The coral spreads as a thick mat, but species identification requires microscopic skeleton examination.

Close-up of vibrant coral formations illuminated with blue and green hues under ultraviolet light.
Figure 12. Photo with ultra blue light source and amber filter on camera

images WITH White light with photoFlash

Figure 13: Mustard Hill Coral or Related Species

Using white light flash, this photo captures a yellow, bumpy stony coral, likely a mustard hill coral (Porites astreoides), star coral (Orbicella spp.), or brain coral. The coral features a massive, uneven surface covered in small polyps. An encrusting goup of organism is growing in the cavity of the stony skeleton devoid of polyps. These corals are native to shallow, warm Caribbean reefs and play a critical role in reef-building.

A close-up view of a textured yellow coral formation with green algae growth visible in its center, set against a blurred underwater backdrop.
Figure 13. Photo illuminated by white light flash.

Figure 14: Diseased Brain Coral

This image shows a brain coral suffering from disease with evident demineralization and erosion.

Close-up of a large coral formation on the ocean floor, surrounded by diverse marine life and coral reefs.
Figure 14. Photo illuminated by white light flash.

Figure 15: Boulder Brain Coral (Colpophyllia natans)

This photograph shows Colpophyllia natans, a common and large brain coral in the Caribbean. The coral displays wide, meandering ridges and valleys with contrasting colors. Fine, narrow lines (septa) running from ridges to valleys help distinguish this species. Boulder brain coral forms massive colonies and is a dominant reef-builder in shallow environments. It is currently considered vulnerable due to climate change, acidification, and disease. The central area in the image shows disease-related polyp loss.

A close-up of a brain coral showcasing its textured surface, with an area of orange and red coloration and some algae growth, set against a sandy ocean floor.
Figure 15. Photo illuminated by white light flash

Figure 16: Symmetrical Brain Coral (Pseudodiploria strigosa)

This image likely features a Symmetrical Brain Coral, forming a dome-shaped colony with convoluted valleys and rounded ridges. The coral is yellowish-tan with darker areas, lacking the groove found in some related species. Pseudodiploria strigosa is widespread in Caribbean shallow waters, slow-growing, and foundational to reef habitats, supporting symbiotic algae (zooxanthellae) for photosynthesis.

Note the irregular loss of polyp growth on the surface of central and right side of the specimen. This is consistent with the result of spreading SCTL disease. Additionally, the adjacent coral is completely overrun by the opportunistic algae.

Close-up of a coral formation covered in algae on a reef, with a date stamp in the corner.
Figure 16. Photo illuminated by white light flash

Figure 17: Lettuce Coral (Agaricia spp.) and Codium Macroalgae

The image features a ruffled lettuce coral (Agaricia spp.) (Agaricia agaricites or Agaricia tenuifolia} and green branching macroalgae (Codium). The coral forms undulating plates or branches, often yellow-green or brown. 

Substantial polyp loss and algal overgrowth are evident. The accompanying Chlorophyta Codium macroalgae, known as green sea fingers, have a distinctive branching structure absorb nutrients like nitrates and phosphates from the water. 

Close-up of green coral and marine plants on a rocky substrate, showcasing intricate textures and vibrant colors.
Figure 17. Photo illuminated by white light flash

Figure 18: Field of Broken Coral

White light photography reveals an expanse of broken, lifeless coral, a few healthy finger corals, and one small fish.

An underwater scene featuring colorful coral reefs and a fish partially hidden among the coral.
Figure 18. Photo illuminated by white light flash.

Figure 19: Pillar Coral Disease Progression

This image of one of the pillar coral species shows a pattern of disease spread from the bottom to the top where the top appears relatively healthy in this daylight exposed photograph. The lower two thirds are bare of polyps. This area has been overrun by algae. 

Underwater image of a brownish coral formation surrounded by green and colorful marine plants.
Figure 19. Photo illuminated by white light flash

Figure 20:

This image of a collective variety of stony corals in various states of disease progress.  A patch of polyp covered coral is on the lower left. Exposed stone is seen in the central area. The remainder is covered by several opportunistic algae species. The images in the distance are overrun by SCTLD and covered with algae.

Underwater coral reef with various textures and green plants, captured in natural lighting.
Figure 20. Photo illuminated by white light flash

Figure 21: Snakelocks Anemone (Anemonia sulcata/viridis)

The organism shown in Figure 21 is likely a Snakelocks anemone. This finding is new to me. It is an invasive species out of its eastern Atlantic / Mediterranean range. Its tentacles are long and flowing, colored green, grey, or light brown, and tipped with violet or pink. Symbiotic algae embedded in its tissues supply nutrients through photosynthesis. Predatory by nature, it uses stinging cells to immobilize prey, although its sting is mild for humans. There were no observable mutualistic anemone fish. This supports the suggestion that these are indeed invasive.

A vibrant underwater scene featuring a green sea anemone with long, flowing tentacles, surrounded by colorful coral and marine plants.
Figure 21. Photo illuminated by white light flash

Figure 22: Chocolate Brittle Star (Ophiuroidea cinereum)

The organism in this image is likely a brittle star, endemic to the Gulf of Mexico and known as the Chocolate Brittle Star.

A close-up view of an octopus on the ocean floor, surrounded by rocks and marine vegetation.
Figure 22. Photo illuminated by white light flash.

Figure 23 – 24: Finger Coral (Porites spp.)

This image displays a branching finger coral, common in the Caribbean, with short, blunt, finger-like lobes. Porites typically have thicker branches, while Porites furcata features thinner, rounded tips. Both can appear green, yellow, or greyish, with color and growth form influenced by habitat conditions.

Close-up view of colorful coral formations underwater, showcasing green and yellow hues and various textures.
Figure 23. Photo illuminated by white light flash

This enlarged view of Figure 23 depicts relatively healthy coral with no signs of Stony Coral Tissue Loss Disease (SCTLD).

Close-up view of colorful coral formations under the sea, featuring vibrant green and yellow hues.
Figure 24  This enlargement image of Figure 23 shows relatively healthy coral without signs of SCTLD

Conclusion:

All stony coral varietals seem to be subject to the same disease. The progress of the disease is unchecked and is advancing. The algae may be flourishing because of increased nutrients in the areas resulting from decomposing polyps and because they are optimizing an echo-niche left vacant by the polyps. The algae are not rebuilding the reefs. The fish population is also in great decline probably secondary to the degradation of the reefs.

Personal Commentary and Reef Health Summary

After thirteen dives across six reef sites in Roatan, Honduras, the overall impression was a declining reef system. Notably absent were turtles, large fish, sharks, lobsters, tunicates, and nudibranchs. The reef, once vibrant, now stretches for miles as broken, gray-brown expanses covered by algae. Invasive species observed included lionfish, a single anemone, Tubastraea faulkneri coral, and two spiny urchins. Only small fragments of some coral species persist, with no Elkhorn, Pillar, or Staghorn forms present and much of the previously widespread fluorescence now largely gone. While some sponges and fans remain, the images presented here document the few surviving patches of live coral polyps amid non-fluorescent, algae-covered stone skeletons.

Plan for remediation:

Problem Statement

The Stony Coral Tissue Loss Disease is relentlessly advancing and destroying the vital surface of the stony reefs. The cause of this disease is not yet discovered. This is a continuing catastrophic event. Work is in progress and includes maping, determining the progress rate and direction of spread. The causality and cure are not yet determined.

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4 responses to “Fluorescent Photography Highlights Coral Health Issues”

  1. Cindy Avatar
    Cindy

    You examined so many varities of coral. It is very disheartening to learn how badly the disease is treating the reef. If you can determine the primary cause that will be wonderful, and a first step to treatment.
    Cindy

    1. John Knapp Avatar

      There is so much unknown about diseases in the ocean. This one is devistating and the cause is unknown. Hopefully the project that I planned will make some difference.

  2. Manuela Klopper Avatar

    It is devastating seeing the reefs dying and nearly everything else with them. I stopped scuba diving some years ago and I am happy to have seen beautiful reefs in many parts of the world.

    1. John Knapp Avatar

      Yes. Caribbean diving was my first salt water experience now I am reluctant to return. I am so anxious to see some reversal of marine life there.

Stony Coral Tissue Loss Disease: Threatening Caribbean Reefs, Wildlife and Ecosystems

This is a follow-up publication on Stony Coral Tissue Loss Disease. It describes the findings in the coral reefs in the Cayman Islands during a week in mid April, 2024. The travel to the island was reasonably easy and the accommodations onboard the live-aboard cruise were good. The conditions of the reef life and tropical fish however was disheartening. We have a big problem.

The featured image was made from a view of the sunset from the port on Grand Cayman island. The sunset may be symbolic of the future diving in the Caribbean. I hope that there is a recovery in the future.

As reported in four previous posts (Death in Paradise), there is a continuance of even greater proportions seen during this trip. I reported on the findings on the reefs around Roatan Island off the coast of Honduras two years ago. The condition of the reefs showed considerable loss of the polyp life because of Stony Coral Tissue Loss Disease (SCTLD). It was quite extensive and showed nearly 70% loss of life. At night the coral showed a significant loss of fluorescence because of the large dead areas of coral polyps. During the day one could see the areas of exposed stony skeleton of the reef.

The reef at multiple sites of the Cayman Islands including Grand, Little and Brack, has been devastated by the disease. The population of the reef fish is also significantly diminished. I did not make a count of the fish or of the areas of dead coral. Because of the extent of the dead coral there was no reasonable way for me to make an accurate comparison. It was very distressing. With the option to make 20 dives I made only 12. There was nothing worthwhile to see. I would estimate more than 80% to 90% loss of polyp life. 

In conversation with other experienced divers on board the ship they said that they saw similar conditions across many of the Caribbean islands from Bonaire to the Mayan coast. Generally, they were unaware of the cause of the polyp depletion but said that it looked the same as in the Caymans. The less experienced divers were unaware of the problem and were happy to be in the warm water (85.5 degrees F). There was still some interesting wildlife but is was very reduced when compared to the concentration I had seen as little as 5 years ago. 

50% of central coral head is dead. All of the surrounding coral is dead.
Coral completely over run by SCTLD.
70% of brain coral is dead. Surrounding coral is lifeless.
nderwaterOther areas typical of the reefs showing the discruction of the polyps.
Lion fish (Invasive)
Caribbean Spiny Lobster (Panulirus argus) It was good to see a lobster but formerly there were dozens.
Mating Flamingo Tongues (Cyphoma gibbosum)
Lettuce Nudibrank (Elysia crispata)
Hawksbill turtle (Eretmochelys imbricata) Critically endangered.
Rough file clam (Ctenoides scaber). Similar to the disco-clam seen in the Palau reefs.

There was still life in the Caribbean but it may be below the 100-foot depth accessible for divers and also for much of the live that requires light. The life forms that were readily apparent were mostly bottom feeding animals. Sponges and soft fans were still alive and did not seem to be affected by the SCTLD.

The effects upon the economy that are a result of reef polyp loss are not readily available, however, many of the recreational hospitality workers are questioning their future employment opportunities. I suspect that there may be some resistance in these businesses to make these issues more public.

There has been some publication of the research into the cause of the disease and it seems that researchers have identified an infection. “Results suggest that the bacterial community may be involved in SCTLD, but other members of the holobiont (i.e., viruses and Symbiodiniaceae) may contribute to lesion progression”.1, 2

Vectors and process of viral action is not yet publicized 3. One should not expect a recommended solution for a cure until much further research will be done. I anticipate that it may take decades and that the reef corals will not survive at the current rate of disease progress. This has a direct impact on the southwest coast of Florida.

If you have observed the effects of SCTLD in other areas of the Caribbean or other places in the world please engage in the SCTLD dialogue in the discussion board.

References: Where 2. and 3. are specifically related to work done in Florida reefs.

1. A meta-analysis of the stony coral tissue loss disease microbiome finds key bacteria in unaffected and lesion tissue in diseased colonies

2. Microbial Community Shifts Associated With the Ongoing Stony Coral Tissue Loss Disease Outbreak on the Florida Reef Tract

3. Viral-Like Particles Are Associated With Endosymbiont Pathology in Florida Corals Affected by Stony Coral Tissue Loss Disease

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#SCTLD #Stony coral tissue loss disease #coral #turtle #nudibrank # Flamingo tongue #coral polyp #file clam

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