The coral on your frame is thriving. The fragments attached at the beginning are growing very well. All the fragments of this digitate Acropora are now fusing together. We applied the micro-fusion technique that has been described by the Mote Marine Laboratory in Florida. In particular, when putting fragments of the same genotype close to each other they can stimulate the fusion of these fragments, speeding up their growth rate. When doing coral frame restoration or maintenance we usually apply this technique when we find a huge broken colony. We cut off small branches and then we attach them very close to each other as you can see here.
The Chromis viridis , known commonly as green puller, has found in your coral frame its home. This particular fish is known also as green damselfish. They only reach an adult size of 3-4 inches (7.6-10 cm).There are several contestants for the title of most important reef fish family, but the Damselfish are certainly one of the front-runners. Not only are there numerous species, but also many of these species are present on Maldivian reefs in prodigious numbers. The green damselfish that you can see in the picture is associated with isolated coral heads in sheltered inshore habitats. Like all damselfish, they can be territorial and aggressive, especially as they get older.
Coral reefs are built and made up of thousands of tiny animals called coral “polyps” that can live individually (like many mushroom corals do) or in large colonies that comprise an entire reef structure. A polyp has a sac-like body and an opening, or mouth, encircled by stinging tentacles called nematocysts or cnidae (imagine an upside down jellyfish). The polyp extracts calcium and carbonate ions from seawater to build itself a hard, cup-shaped skeleton made of calcium carbonate (limestone). This limestone skeleton protects the soft, delicate body of the polyp. Coral polyps are usually nocturnal, meaning that they stay inside their skeletons during the day. At night, polyps extend their tentacles to feed. Most coral polyps have clear bodies whereas their skeletons are completely white, like human bones. Generally, their brilliant color comes from the zooxanthellae (tiny algae) living inside their tissues. Several million zooxanthellae live and produce pigments in just one square inch of coral. These pigments are visible through the clear body of the polyp and are what gives coral its beautiful color.
Meet Toby …
The Black Saddled Sharp Nose Pufferfish (Canthigaster Valentini) also known as the Saddled Toby, is a very common sight in Maldivian waters, being found on reefs, rocky outcrops, lagoons and grass beds. Tobies swim using their pectoral fins, although they can make surprisingly fast bursts, they are not strong or fast swimmers. Perhaps to make up for their relative lack of mobility, they have a symbiotic relationship with bacteria such as Pseudoalteromonas tetraodonis. This bacteria produces tetradotoxin which is a powerful neurotoxin. These tetradoxin’s are found in their skin and internal organs. Tetradoxin is extremely poisonous and is approximately 100 times more toxic than cyanide. This gives them protection against predators.
Despite the protection given by the frames, everyone and everything is exposed to predators eventually! Jackfish or trevallies are among the most common predators patrolling the reef. They feed on reef fish and crustaceans. The juveniles inhabit sandy inshore protected areas while adults may be found in lagoons or protected and exposed reefs. Although the increasing pressure from fishing and recreational fishing activities persists, there is no sign of decline of the population according to the International Union of Conservation of Nature (IUCN). Unfortunately, the photo is a little out of focus since we were focused on the maintenance of the frame and not ready to capture this encounter, but we still think that this is a nice shot!
This is your 6 month frame progress update. Unfortunately your frame is struggling!
Looking at your frame, we can notice lots of bleached corals as well as dead coral fragments. Unfortunately the warm months of March, April and May have been really rough on your frame. We are trying our best to keep the damage to a minimum by cleaning harmful algae off bleached corals. We also started moving extremely bleached frames under the Water Villa Restaurant to protect them from further damage through UV radiation. We hope to see some of your bleached corals recover over the next couple of months, but it will be a slow process. Now that the water temperatures are slightly decreasing the next step of action will be to replace dead coral fragments with new healthy fragments.
Over the following months we will continue with maintenance to keep harmful algae and predators off your frame and to give your frame the best chance for successful growth.
We’ve had another very warm spring this year; March, April and May have been consistently warm and lead to a lot of coral bleaching on many of our frames as well as the house reef. Because your frame has been showing extreme signs of bleaching, we decided to move it into the shade. Your coral frame will be under the Water Villa Restaurant until we see your corals recover.
Research shows that corals can display bleaching from high temperatures but also that UV light can damage already stressed corals. This is one of the reasons we moved your frame out of the direct sun light and into the shade. Furthermore the temperatures in the shade are a little lower than the exposed sunny spot your frame used to call home.
Over the next couple of months it is one of our priorities to clean your frame frequently to minimize harmful algae from smothering your coral frame.
We have some unfortunate news this month as we are starting to see some evidence of bleaching around the coral frames. Coral bleaching can be ascribed to warming ocean waters for extended periods of time where the symbiotic algae (Zooxanthellae) living inside the tissue coral is expelled by their host and in turn leave behind a bleaching white skeleton. This algae shares a mutualistic relationship with the corals; the coral provides shelter to the algae and in turn the algae can provide as much as 90% of the nutrients produced by photosynthesis which is used towards their growth. Corals can survive bleaching events such as this, but if they are subject to more stress or prolonged heated waters, they will surely die. Unfortunately, your frame is also showing major signs of bleaching of around 60%. This is a rough estimate based on the amount of bleaching fragments of the entire frame. As you can see from the images, their white skeletons are not something anyone can miss, especially in the water. The degree of bleaching on your frame varies from fragment to fragment and ranges anything between minor bleaching on the branching tips, those bleached on the surface (those directly exposed to the sun’s rays), intermediate bleaching (still some symbiotic algae present) and/or completely bleached. We have also noticed that there is some “glowing corals” on your frame. Corals produce a fluorescent chemical which act like sunscreen to protect them against increasing heated waters caused by climate change and as a result produce the most vivid colors, although spectacular to look at, this is the ultimate warning that our oceans are in trouble.
Unfortunately, there is not much we can do at this stage, but wait to see whether they recover or not in the next months. Should they not recover and they are completely dead, they will be removed from the frame and replaced with new live ones. This is of course a major setback for our coral conservation project, but it is also the reality we are dealing with today.
As you can see from the picture, your coral frame are colonized by some little, brown and green organisms called Ascidia. The species is called Didemnum molle (also known as the green barrel sea squirt or the green reef sea-squirt.) and is very common in the Indo-Pacific area. Ascidia is a filter-feeder, feeding on suspended plankton and detritus and its green color is given by the algae living in symbiosis with them, in this way the algae is protected by the predation and the Ascidia can receive energy from its little hosts. Luckily they don’t possess any threat to the corals when they are few in numbers, however they can colonize quite quickly on the frames through asexual budding, as such they are regularly removed to minimize competition with growing corals.
Corals are subject to predation by many organisms such as mollusks, crustaceans or echinoderms. Among those, coral eating fish are also included such as the Parrotfish or the Titan Triggerfish. In this picture, you will notice that many of the tips of the branches have been removed or damaged, possibly by a parrotfish. Parrotfish species are herbivores that spend much of their time eating algae that is covering rocks and dead corals, or the unicellular algae contained in the coral tissue. Thus, in this case they may have removed part of this digitate Acropora because of its high content in unicellular algae. The damage is not disastrous and the white scars will soon recover as you can see from the tips where small polyps already forming
In some unfortunate cases, much like we can see in nature, there are some dead fragments on your frame such as this one pictured. This is often the result when corals undergoes very high level of stress where they cannot seem to recover. This is not because your frame isn’t suitable, but since all the fragments were collected from the sand they already received lots of stress before attached onto your frame, so it happens from time to time that fragments might receive further high stress levels due to increased water temperatures and they lose the symbiotic algae Zooxanthellae that they need to survive. They will turn bleach white and if stress conditions persist they will die completely since they have no more animals for feeding or defending the corals and then they are often competing with invasive algae that grow over the polyps when this happens they will also die off. During the maintenance these pieces of dead coral is usually removed while the live part remains attached.
Looking at your frame, you will see that it is doing amazing and the corals are really growing well since the last update, even after the heated months and some stormy weather. We have done some recent maintenance on all the frames which include cleaning them, removing the invasive algae and coral predators to maximize growth. In the upcoming post we will show you close-ups of your frame and the coral fragments, with some interesting facts and findings about those that are on your frame. After 6 months you will see a similar post showing once again the progress of your frame.
Acropora corals are among the most common genera of corlas in tropical reefs. Corals are composed of tiny individual polyps each that resembles an upside-down jellyfish with the mouth in the middle, surrounded by the tentacles. Here you can appreciate the tiny polyps in this picture. Furthermore, Acropora corals are called hexacorallia since each polyp has six, or multiples of six, tentacles. Such structures are used for hunting prey, microorganisms, but also used for defence. These tentacles are armed with unicellular weapon needle-like composed with a strong mix of toxins. Humans are not harmed by these toxins but it may cause inflammation along with some itching if touched.
