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Longfin Batfish Sightings from the St. Anthony Wreck on Maui





One of the very best things about diving in the same area for years is learning about the lives of the individual animals who live there. To make this possible, the animal must have features or markings that make it identifiable as an individual, so that it can be recognized over and over again over time. These features can include a missing fin or tail, damaged part of the body, or a distinct color pattern.



A Longfin Batfish on the St. Anthony Wreck, Maui. Oct. 2016.

It also helps if the animal is rare, because that causes us to notice it in the first place! Last month one such rare fish appeared on the wreck of the St. Anthony off of Maui. A Longfin Batfish (Platax teira) was observed by Autum Hill swimming around inside the cabin on Sept. 7.


This species is not considered native to Hawaii, so initially this individual was thought to be an aquarium release (home aquarium keepers often buy fish as juveniles, but if the fish get too big for the tank, regrettably people sometimes release them into the ocean). However, according to at least two have been reported off Oahu, one off the Big Island and another off nearby Johnston Atoll (Kalama Atoll) only 860 miles to the southwest, so it is possible that an occasional larval individual drifts here naturally from elsewhere in the Pacific or arrives as a juvenile under floating debris.


What made last month’s sighting at the St. Anthony wreck of even more interest is that there have been several other sightings of a Longfin Batfish on the St. Anthony as far back as Dec. 2003. Here’s what we know about the 2003 individual:


On Dec. 15, 2003, Bo Lusher and Andy Schwanke were diving in 85 feet of water off Pu‘u ola‘i, Maui at a site called the 85 ft. Pinnacle, and saw the first Longfin Batfish we had ever seen in Hawaiian waters. INCREDIBLY, the next day a Longfin Batfish was seen on the St. Anthony wreck about 3.5 miles away. Because Andy had taken a photo of it on the 14th we were able to compare the color pattern and tears in the fins and, as you can see in the photos below, it was the same fish! He or she had swum a distance of over 3.5 miles in one day.


Left: Longfin Batfish (Platax teira) at the 85 ft. Pinnacle on Dec. 15, 2003. Right: Same Longfin Batfish seen the next day 3.5 miles away on the St. Anthony wreck on Dec. 16, 2003 (Photo taken Dec. 17, 2003 P. Fiene). Note identical tears in dorsal fin and tail fin.


Initially he stayed inside the cabin of the wreck, but after a couple days he began swimming around the wreck in the open. He stayed for a few weeks during which time our divers were treated to seeing a fish not normally found in Hawaii. But then one day he was no longer there.

Then in January of 2005 David Fleetham photographed a Longfin Batfish on the St. Anthony again! We were thrilled to be able to use his photos for comparison and to learn that this was the same fish – 1 year older! The cuts in the dorsal fin had healed, but the color pattern could still be used for identification. He resided there again for awhile and one day was gone.

Two other Longfin Batfish sightings and photos from the St. Anthony in March of 2011 and now in September of this year (2016) allow us to compare photos again. Is this the visiting batfish from previous years?


As you can see above, this is not easy to discern. At a glance, it hardly looks like the same individual. Every camera and lens renders a difference in color and aspect ratio, and the fish is almost never in exactly the same position in relation to the camera. However, if you have a few days to spend comparing the photos I think you will agree that it is the same individual! A 13-year visitor to the wreck.



Making identification potentially trickier is the fact that this species of fish apparently sometimes changes color in parts of his body. In the photo on the right, notice the large black areas on part of the dorsal fin, back of body, caudal peduncle and anal fin. David Fleetham was inside the cabin of the wreck and was within a foot of this fish when photographing him with a wide angle lens. Perhaps the fish was stressed in the confines of the cabin with a diver so close and was exhibiting stress coloration, because this black area does not appear in the photo that he took right before this or in any of the other photos of this individual from other sightings.



Judging by the tears and bites in the fins, life is not the easiest wherever he normally resides. In fact, Dr. Jack Randall says, “It is surprising that this species survives, because it is so exposed most of the time, far from shelter, and because it is not a fast swimmer.”


And now, as of Oct. 18, he is gone again, after being last sighted by Rachel Domingo on Oct. 16. His five week stay on the wreck went all too quickly. What other home(s) does this fish have? What makes him return to the St. Anthony? Surely there is an innate urge to find a mate – a hopeless exercise in Hawaii where they are not normally found. Could that be the impetus for his repeated visits to the wreck?


We will never know why he returns, but thanks to observant divers and underwater photography we at least know who this fish is. Knowing that this is the same individual again and again is like knowing a little secret about the life of one fish in the sea.




Written by Pauline Fiene. Photos as credited. Thanks to Andy Schwanke, Benja Iglesis, David Fleetham and Rachel Domingo for photo usage.

Coral Bleaching Report on a 500-year-old lobe coral colony at Olowalu


This summer’s and fall’s high ocean temperatures and sunlight intensity have taken the lives of thousands of coral colonies in Hawaii. Some places have lost large amounts of colorful, vibrant coral reefs and in their place is a covering of dark brown algal turf. It has brought some people to tears.


Last Saturday morning DLNR held an event called Bleachapalooza which encouraged snorkelers and divers to go out and report on the status of their favorite reef; to take notice of the reef composition, percentage of bleached coral, which species were bleached, etc. Then they were asked to fill out a form on the Eyes of the Reef website to add to what is known about the extent of bleaching at this point in time – a sort of “State of the Bleach.”


So, to participate, I headed over to Maui’s cherished reef at Olowalu. I had been there the week before in a very shallow part of the reef and had come out of the water in tears. Although this had all been predicted, I had not been able to envision what it would look like if large areas of coral subsequently died after bleaching. I did not want to go back – at least not until months had passed and some recovery could be seen.


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Lobe coral colony (Porites lobata) at Olowalu estimated to be about 500 years old. As seen on Google Earth.

But in honor of the event I did go back for a very specific reason. I went to visit a particular coral colony that has special meaning to me. It is one of the oldest circular coral colonies at Olowalu. Measuring at about 25 feet in diameter, it has been estimated to be about 500 years old*, and is so large that it can be easily seen on Google Earth.


Hovering in the water in the presence of this coral elder is like visiting a museum and beholding an incredible sculpture from another age. This colony, and others in its age class, precedes Western contact! Just imagine everything that has taken place on land during this time, while this one particular colony quietly grew, partly died back during unfavorable conditions, then grew some more…


This is what it looked like from underwater in August of 2013. Even then there were areas of die-back among the living parts, but most of it was alive. It was an impressive sight.

Olowalu giant 500-year old colony

Estimated 500-year-old lobe coral colony (Porites lobata) at Olowalu photographed on Aug. 24, 2013. Photo by P. Fiene


From what I had seen the week before, I had very little hope for what I would find. The water was not the clearest and as I approached the dark silhouette in the distance I was expecting another wrenching sight. BUT – most of it is surviving! Yes, there are patches that have recently died and are covered by algal turf, and yes there are still several weeks ahead of higher than desirable water temperatures, but at this time it has not died as so many thousands of coral colonies here in Hawaii already have.


Olowalu 500 year old colony Oct. 3, 2015 for blog

Estimated 500-year-old lobe coral colony (Porites lobata) at Olowalu photographed on Oct. 3, 2015. Photo by P. Fiene


Should we be surprised? The saying that “old age isn’t for sissies” may hold true for corals too. For this colony to have survived hundreds of years it must have adapted to many different environmental conditions along the way, some of them unfavorable and challenging. It is suffering again now, to be sure, but as of Oct. 3 it is still alive!

We will keep you posted about this very special coral colony in the months ahead.


by Pauline Fiene


*Rough age calculated by dividing the 25 foot diameter in half = 12.5 feet. Converting to centimeters = 381 cm. Then dividing 381 cm by .71 cm (Edmondson’s mean linear growth rate per year for 10 Porites lobata colonies) = 537 years.

Edmonson, C.H. 1929. Growth of Hawaiian Corals. Bernice P. Bishop Museum, Bulletin 58, Honolulu, Hawaii.


Coral Bleaching – Is that white coral dead?


As scientists so accurately predicted, we are experiencing a historically high amount of coral bleaching this summer/fall in Hawaii. One of the questions that we are frequently asked is, “Is that white coral dead?”

Living corals in their healthiest state are shades of tan, yellow, brown, and green, among other colors. The color they exhibit comes mostly from microscopic single-celled algae called zooxanthellae that live in the coral’s tissue and provide the coral with most of its food.

When the water becomes unusually warm and light intensity increases, the zooxanthellae increase their photosynthesis. As a result the concentration of free radicals, which are a byproduct of this process, exceeds what the coral can deal with, causing membrane damage to the coral. At the same time demand for nutrients by the zooxanthellae increases and exceeds what the coral can provide. Super simplified, it is believed that these two factors together trigger expulsion of the algae by the coral. It is a survival mechanism.

unbleached and bleached colonies

Two cauliflower coral colonies. The one on the left is healthier. The one on the right has expelled its microscopic algae and is referred to as “bleached.” Photo P. Fiene

Once the zooxanthellae are gone – a condition known as “bleaching” ­– the coral’s white skeleton is clearly visible through the transparent coral tissue and the coral appears dead! (colony on the right in the photo above)

One of the first species to bleach here in Hawaii is cauliflower coral (Pocillopora meandrina). During the third week of September a very high percentage of cauliflower coral colonies at Molokini bleached. Interestingly, the percentage of bleached cauliflower coral is less in water shallower than 30 feet (where presumably the corals or their zooxanthellae are more adapted/acclimatized to high light levels/temperatures and therefore are not experiencing as much “stress”) and deeper than about 90 feet where sunlight is not penetrating to such an extent and temperatures are lower. So at Molokini, the bleaching is greatest between 40-90 feet – the exact depths we are diving.


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Although these cauliflower coral colonies at Molokini have bleached, they are still alive in this photo from Sept. 23, 2015. Photo: P. Fiene


This leads to some of our divers asking if the bleached cauliflower coral is dead. And the answer is – not so far. Here’s how you can tell.


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Tentacles of cauliflower coral polyps indicate that the coral is still alive, despite being bleached. Photo P. Fiene

1. Take close-up photos. As a diver, it is not easy to determine if a bleached colony is alive by simply looking at it, but if you take close-up photos you will see the extended tentacles of the polyps. That indicates that the coral is still alive at this time. It does not mean that all is well, however.


Corals derive most (up to 90% in some cases!) of their nutrition from their microscopic algae, so during a bleaching event when the algae are absent, the corals are beginning to starve. They can acquire some energy by capturing food particles with their tentacles, but this is not enough to sustain them long-term. So the ability of bleached corals to survive depends largely on how healthy they were when bleaching occurred, how much lipid (fat) they had stored, how well they can acquire food particles from the water column and how long the temperature remains at a stressful level.


The sooner the corals are able to re-populate their tissue with algae and get back to normal, the better chance they have to survive. But for this to happen the water temperature and sunlight intensity have to drop below a certain threshold – something that is not predicted to occur for at least three more weeks according to this excellent NOAA bleaching forecast.


There may be a positive sign in the close-up photo of the coral’s tentacles above. Cauliflower corals store the lipid (fat) in the tips of the tentacles and perhaps elsewhere in their tissues. In the photo, you can see the opaque white tentacle tips indicating that this coral colony still possesses a store of energy. Will that be enough for this coral colony to survive several more weeks until the water temperature drops below the bleaching threshold?


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The presence of coral guard crabs (Trapezia spp.) indicates that the coral is probably still alive, despite being bleached. Photo P. Fiene

2. Look for coral guard crabs in branching species. 

If they are present, then the coral is probably still alive. This is because the crabs and the coral have a very close relationship. The coral provides the crabs with a home, nutrition in the form of mucus, and even more food in the form of lipid stored in the tips of the tentacles. The crabs in turn provide protection against predators such as the crown-of-thorns sea star, as well as increase water circulation among the coral’s branches, among other benefits.


These crabs are not easy to see however. At night they are actively moving about the colony. But during the day they are deep within the branches. Very close observation and a light are necessary.


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Part of this cauliflower coral colony has died and tan turf algae has colonized the dead branch tips. Photo P. Fiene.

3. Look for evidence of turf algae beginning to grow on the coral skeleton.

When the coral is alive the coral’s tissue produces mucus which prevents turf algae (tiny seaweed) from finding a place to grow on it. If a colony or part of a colony has died there is no longer tissue to prevent turf algae from colonizing the surface and beginning to grow. If you see a brownish or greenish coating on the white skeleton, then at least that part of the coral colony is no longer alive.



Right now we will have to wait and see what percentage of corals in Hawaii will be resistant to bleaching or will “survive” the bleached state by re-populating their tissue with microscopic algae. Molokini’s reefs are faring better so far compared to the high mortality in some places around Maui. However, even if most of the corals at Molokini survive this year’s bleaching, they may experience reduced reproductive ability, reduced growth or reduced immunity. For now, at the beginning of October, we are hoping the outcome will be one of survival rather than one of recovery from a severe die-off.


An excellent source to learn more than you ever wanted to know about coral bleaching can be found here:


by Pauline Fiene


“Birth” announcement from a Maui Reef – Can you identify this baby fish?


baby announcement new 2 crop with border



Spring is here!


Spring on Maui means that whale season comes to a close, the water starts to warm up, corals begin releasing their eggs and sperm into the water during their annual spawning events, and new baby fish begin to settle out of the plankton onto the reef.


The spring and summer months are prime months for baby fish settlement. These fish have spent weeks or months as larval fish developing up in the plankton, and when the time is right they leave the plankton and seek an appropriate reef to begin their life as juvenile fish.



Sometimes these settlements of fish number in the thousands or even – in historic years such as 2014 – in the millions of a single species. But the vast majority of fish species settle in smaller numbers with no fanfare, without our awareness. They are tiny, and they remain tucked into crevices in the reef until they are large enough to be less vulnerable to predators and until they are better able to defend themselves.


It is so rare to see these new arrivals – those that have literally just dropped out of the plankton the night before or two nights before – that it is almost like witnessing a birth when you see one!


baby puffer 2735IMG_2735 for blogI was in the “birthing room” today during a dive. As I reached out to pick up a stick on the sand, a tiny black thing darted a couple of inches. It was so tiny and so unremarkable that I hadn’t even noticed it. At first I thought it was a squid, but as I looked more closely, it appeared to be a tiny pufferfish.


At half-an-inch in length, this little guy already had the shape and proportions of an adult pufferfish. He had delicate fins in the right proportions and he even had an exquisite, tiny version of an adult pufferfish mouth. Any pufferfish parents would surely have said, “He’s perfect!”


He was so dark though, and appeared to have no distinguishing color or marks, that I never thought I would be able to identify the species of pufferfish he was.


baby puffer 2990IMG_2990 for blog

However, as I photographed him, over a few minutes, he turned lighter and lighter in color, revealing markings that gave away his identity! At less than the size of a dime he is an almost perfect miniature of an adult!


Can you identify which species of pufferfish this little guy is? Click here to find out if you’re right :-).



The Life and Times of a Humpback Whale Barnacle


whale barnacle on bottom for blog

Last week we were treated to an unusual find during one of our dives off of Maui. There on the sand was a strange, black, partially-circular object composed of radially symmetrical segments. Was it plastic? Metal? With that symmetry, surely it was man-made.

But no, we’d seen something like this a few years before – it was part of a whale barnacle! Ten feet away from it we found its other half.



Every winter we keep our eye out for these lucky finds. Sometimes we find them soon after they have fallen off. If that is the case, the underside of the barnacle is covered with black whale skin (this one even had the flesh of a different species of barnacle, a gooseneck barnacle, still attached to it). If we find one months later, it has been picked clean by marine organisms.

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Left: Whale barnacle found (in two pieces) soon after falling off a whale, showing black skin embedded in barnacle (60 mm). Right: Barnacle found months after falling off of whale, picked clean by marine organisms. Photo: P. Fiene.


Until this year, all the barnacles we’d found had been intact. This one was unusual in that it was broken into two pieces. We don’t know exactly why. But, it allowed us to see – and not just read about and imagine – one reason the barnacle’s white shell stays so firmly attached to whales during the thousands of miles of migration, during their spectacular breaching, and through all sorts of sometimes violent male-on-male aggression. More on that later.


A humpback whale can have up to a thousand pounds of these barnacles attached to it! This may sound like a lot, but when compared to how much a whale weighs (35-40 tons), hundreds of pounds of barnacles on a whale is comparable in weight to, say, an aloha shirt and slippers on a human. And these are not just your garden variety barnacle. They are Coronula diadema, a species of acorn barnacle that lives only on whales, primarily humpback whales.*


whale barnacles on tail-A.Schwanke

Barnacles live on many parts of a humpback whale, from the throat area to the pectoral fins to the tail as seen in this photo taken off of Maui by Andy Schwanke.


Barnacle species that have evolved to live on whales are treated to a constant flow of water from which they can strain food particles. The barnacles position themselves in the places on the whale that experience the best water flow characteristics. It is believed that the barnacles are generally not harmful to the whale and might possibly even be beneficial in some cases as a defense or in competition between males.


Just how do these barnacles get on the whale to begin with? Adult whale barnacles are hermaphrodites. They fertilize the eggs of adjacent barnacles with a (proportionately) very long penis. The fertilized eggs develop into larvae which are then released into the water in the Hawaii wintering grounds. After further development as free-swimming larvae in the ocean, they are able to detect chemicals given off from the whale’s skin.** These chemicals cue the tiny larvae to settle on and attach to the whale’s skin, metamorphose into juveniles, grow, and secrete an incredibly sticky cement that tightly bonds them to the whale. Next, they begin to produce six vertical calcarious plates which will fuse to become the formidable circular shell that the animal will live within.


This shell is not solid material though. Cavities are built into the shell all around its circumference. These spike-shaped cavities pull the whale’s skin into them as the shell grows.*** The whale and the barnacle shell are then almost locked together. Because this barnacle was broken in two we were able (with the help of a Dremel tool) to actually see these cavities for the first time. And, as expected, they were filled with black whale skin! Skin also grows up around the base of the shell, leaving it firmly embedded and making it reportedly very difficult to dislodge.

barnacle crossxIMG_2299editwith arrpws

Arrows show where black whale skin has been “pulled” up into cavities in the barnacle’s shell. Photo: P. Fiene.


Given that the barnacle animal is cemented to the whale and given the interlocking-shell-and-skin configuration, it is a wonder that they ever come off. But they do!


Well-known researchers Mark Ferrari and Debbie Glockner-Ferrari have studied humpback whales in Hawaii for 39 years. They have first-hand knowledge of whales losing barnacles while in their Hawaii breeding grounds. Mark recalls that in 1987 they saw a yearling on separate occasions approximately a month apart. Because this individual was lethargic they were able to approach closely enough to actually see the barnacles and document their disappearance. He estimated that about 50% of the barnacles were lost during this time. And the reason they could tell that barnacles were being lost is because when a barnacle falls off, a perfectly circular scar is left, as you can see in this photo they provided below.

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Whale head showing adult barnacles and circular scars where barnacles have fallen off. Also showing many juvenile barnacles growing around the eye and all over the body. Maui, Hawaii. Photo ©Mark Ferrari, Center for Whale Studies, under Federal Permit #538.



Some of the reasons barnacles fall off have to do with male whales using their barnacle-encrusted pectoral fins as weapons in competitions with other male whales. They might also be knocked off when whales slash at tiger sharks or false killer whales in defense, something Mark and Debbie have witnessed themselves.


But most seem to fall off after about a year as part of a natural cycle. A French researcher reported that humpbacks taken by whalers soon after they had arrived in Madagascar for the winter season had large barnacles attached, but by late winter the whales had no barnacles. Instead the whales had barnacle larvae beginning to attach. By spring, the whales had small adult barnacles.* Photos taken in Hawaii seem to corroborate this approximate year-long life cycle. Scars show adult barnacle loss, while tiny new barnacles can be seen beginning to grow, as in the photos below and above.


Whether they are genetically programmed to die after about a year or whether some environmental factor in their breeding grounds causes them to die is, to my knowledge, not known. Could it be that Hawaii’s semi-tropical waters don’t supply the right (or enough) food, are too warm, harbor diseases (predators,  parasites?) or have insufficient available oxygen for the adult barnacles? Could UV radiation be too intense? Could the whale slough more skin or experience an altered immune response (in turn affecting the viability of the adult barnacles)? Perhaps some of these factors have been examined already but I could not find such studies in my search.


2-21-06, 38 Barnacles CU color, (c) MJF-CWSfor blog

Adult barnacles and juvenile barnacles growing on a whale fluke. Maui, Hawaii. (Long, fleshy gooseneck barnacles can be seen growing on the sides of the white whale barnacles. Photo ©Mark Ferrari, Center for Whale Studies, under Federal Permit #393-1772-01.


Considering the millions of pounds of barnacles that travel to Hawaii on the bodies of the humpback whales, and that many of them are falling off here, it seems surprising that to find one while diving is so rare. But when a barnacle falls off, the odds of it occurring in water visited by divers is small. Divers dive in such a tiny fraction of ocean waters, and usually in water shallower than most whales frequent. When you add the small size of the barnacles to the equation, it begins to make sense why such a find is considered a treasure.


barnacle eating


If we do find one, it is always fun to have our divers guess what it is when we get back on the boat and can talk about it. It isn’t often that they guess correctly. They are faced with what looks like a radially symmetrical white shell with a hole in the center. Most people, if they have to guess, think it is a seashell (a mollusk) of some kind. In fact, even scientists thought they were mollusks until 1830. But a barnacle is actually a type of crustacean – a relative of crabs and lobsters. In fact, if you look at the diagram to the left, you can see that the animal looks somewhat shrimp-like.




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This confusion is artistically captured in the form of the almost life-sized whale statue in Kalama Park in Kihei.





opihi on whale statue

If you look closely at the belly of the whale in the photo to the right, the artist has sculpted not barnacles, but opihi (limpets) attached to the whale! My mind had to do a little flip-flop the first time I saw this. But it’s understandable. Whale barnacles are a strange life form – and few people will ever have the opportunity to find one on the bottom of the ocean, much less see one attached to a humpback whale in the sea.




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Whale barnacles as viewed from above. Broken barnacle on left was found soon after falling off of whale and still has some animal tissue (opercular membrane) visible in the center. Barnacle on the right was found long after falling off of whale. Photo by P. Fiene.


Finding a whale barnacle is the closest some of us will ever come to “touching” a whale. We can’t help but view such a find as good luck. Knowing that this barnacle has traveled thousands of miles on a humpback whale and has fallen off in the exact spot where we are crossing its path is nothing short of spine-tingling.





Written by Pauline Fiene. Photos as credited. Mahalo to Mark Ferrari and Debbie Glockner-Ferrari for sharing their first-hand accounts and documented sightings, as well as wonderfully illustrative photos. Thanks also to Andy Schwanke for use of his whale tail photo and to Cory Pittman for his helpful comments.


*Scarf, James, E. Occurrence of the barnacles Coronula diadema, C. Reginae and Cetopirus complanatus (Cirripedia) on right whales. Sci. Rep. Whales Res. Inst., No. 37, 1986.
**Nagota, Yasuyuki and Matsumura, Kiyotaka. “Larval development and settlement of a whale barnacle” Biol. Lett. 2(2006): 92-93. Print.
***Newman, W. A. and D. P. Abbott 1980. Cirripedia. Stanford, CA, Stanford University Press. Intertidal Invertebrates of the Central California Coast: 504-535. 

Coralline Algae Target Phenomena – What makes those bull’s-eye patterns underwater?


This being National Archery Day (in addition to the much more significant Martin Luther King Day), I decided to finally look into and try to understand something that we see regularly underwater, but that has puzzled me my whole diving career. That is: patterns that look like archery targets which grow on shaded vertical rock walls underwater.

Coralline Target cropped 640 Makena Landing

A Coralline Algae Target with thin rings. Approximately 12 inches in diameter. Makena, Maui. Photo: P. Fiene


I guess I knew early-on that these concentric circles were a type of seaweed called crustose coralline algae. What are coralline algae? They are a group of red algae composed of fused plant filaments that have calcareous deposits within and between the cell walls. The crustose coralline algae look like a thin crispy layer, usually pink or purple, covering the surface of a rock.


In my mind all these years, the striking white concentric circles were the crustose coralline algae, and I paid no attention to the uninteresting background. My eyes saw only the white rings.


But I had it all wrong! The living part is the purple-pink background! The white rings, it turns out, are where the coralline algae has been killed. To finally learn this is poetic justice because I have always been amused when my divers think that bright white coral colonies are extra beautiful, when in reality they have just been killed and the white is the bare coral skeleton.

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Coralline Algae Target with thicker rings. About 12 inches in diameter. Makena, Maui. Photo by P. Fiene


This white ring disease (or complex of diseases?) was named “Coralline Target Phenomena” by Smithsonian coral reef scientists Mark Littler, Diane Littler, and Barrett Brooks in a short paper they wrote for Reef Encounters in 2007*. In the paper they proposed that the white rings are caused by an unknown agent (a bacterium, group of bacteria or other pathogen) that kills the pink coralline algae filaments in discrete concentric strips leaving just the white calcareous part exposed.


They did not have the opportunity to observe a target over time, so they made an educated guess at an explanation hoping that it would elicit information from colleagues. Whatever the agent causing the disease, they hypothesized that the pathogen kills a strip and then “leap frogs” over living tissue to infect ever-larger bands as the circle increases in diameter.


I contacted one of the authors, Barrett Brooks in the Botany Dept. of the Smithsonian, to find out if he knew of any new studies or information on the subject. He replied, “The phenomenon is still entirely open for study. No one, to my knowledge, has focused additional study into the matter.”


He also offered some additional comments to clarify what is known and not known: “Although bacteria were found present in the targets, they could be a result of some lethal activity, and maybe not the cause. How microbes work on reefs is a huge hole in our knowledge. I’m not entirely sure of the cause proposed, nor am I sure that there is only one cause. There is a range of “targets” from small diameter/thin bands, others large with thicker bands. It certainly looks like the bands travel/radiate outward, but who knows… The full answer is still out there.”

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A Coralline Algae Target with thick rings. Makena, Maui. Photo: P. Fiene


Next in my search for a possible explanation I asked marine biologist Cory Pittman and he offered this tentative hypothesis for how the bands might form:


“Assuming the cause is microbial (not necessarily bacterial – the bacteria could be secondary to an initial infection by something else), I wonder if the pattern might result from an interaction between a microbe and a defensive response by the algae? Assume, for the moment, that the agent colonizes a new patch of its host algae (cyst landing, contact with a vector…) establishing an initial point of infection. A colony spreads out from that point killing the underlying algae. The algae around the colony respond by ramping up production of a defensive chemical until it reaches a high enough concentration to suppress the growth of the microbes. The microbes respond by entering a migratory phase and “crawling” forward until they arrive at algae that hasn’t built up enough of the defensive chemical to resist them. Then, they start to consume tissue, again, until the next band of algae builds up resistance. With repetition this forms the target pattern. Meanwhile, the older, resistant bands of algae may begin to slowly overgrow the dead portions..


That would be analogous to how some terrestrial plants respond to attacks by insects. Neighboring plants sense chemicals released by the attacking insects (or the infected plant) and respond by producing defensive compounds that would be too metabolically expensive to produce all the time, but serve to check the spread of the insects ‘when needed’.”


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Photo taken at Makena, Maui by P. Fiene

The photos taken in Hawaii provide some clues regarding the progression of the disease over time. First, at the center of the target the coralline algae shows some re-growth over the dead white rings (yellow arrows) indicating that those rings have been there longer and the coralline algae has had time to recover.


Both green micro-algae and young starts of foliose brown (or red?) algae that colonize the dead surfaces are more prominent on the inner rings (black arrows) than on the outer rings, mirroring the progression of the disease and also suggesting that it takes some time (perhaps a matter of weeks?) for the “targets” to reach their full size.


Coralline Algae Target close-up-Makena Landing copy

Photo taken at Makena, Maui by P. Fiene.



In our Hawaii photos, the coralline algae surrounding the inner rings is often starting to regrow as indicated by the fine white edges (green arrows). The coralline algae around the outer rings shows no such white edge/active growth.






Coralline Algae Target with pink arrows- CP

Photo taken at Hekili Point, Maui by Cory Pittman


Also, some portions of the dead surface in the outer rings still retain faint pink pigmentation (pink arrows) suggesting that those patches have recently died. Again, this emphasizes the progressive formation of the “targets.”







In addition to determining the cause of the “targets,” there are many other intriguing questions to address, such as exactly how quickly the bands are formed, what keeps the targets from expanding to more than about a foot in diameter (in Hawaii), do the other species of algae that colonize the dead surface have any influence on the process, does anything relevant happen at night (just in case something else but a microbe is involved)…

With our curiosity now piqued, we will be keeping our eye out for “targets” to monitor and photograph over time.


by Pauline Fiene


*Mark M. Littler, Diane S. Littler, & Barrett L. Brooks. 2007. Target phenomena on south Pacific reef: strip harvesting by prudent pathogens? Reef Encounter 34:23-24.