Here you will see the partial shape of the cable tie that we used to stabilize this particular fragment to the iron frame. In one month we can already see that this Acropora have started to overgrow this plastic tie and will soon be part of the skeleton forever. Plastic cable ties are a good compromise for attaching corals to the structure, since the material is cheap, resistant and the results are great, however we are looking into using different materials to improve our techniques of reducing plastics in the ocean. When this colony have reached the minimum size for spawning it will release its gametes in the water that ultimately leads to the formation of new colonies elsewhere on the reef
We would like to give some information about this colony of Acropora digitifera that lives on your coral frame. This species forms digitate colonies; the branches may be 1 cm in diameter and up to 10 cm long. This species strongly prefers shallow water. It is usually cream or light brown in color with blue branch tips, but can also be brown with purple tips. It is common near reef crests’ as it prefers strong water movement and it is very common in the Maldives. The most important known threat is the reduction of coral reef habitat due to bleaching, disease and predation. However, it seems to be strong enough to resist to habitat loss more than other species of corals. However, since the current situation with multiple stresses (mainly rising temperature of the ocean) acting simultaneously the species is considered Near Threatened by the International Union for Conservation of Nature (IUCN).
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.
The Dascyllus aruanus, known commonly as humbug damselfish, has found in your coral frame its home. This particular fish is known by multiple common names, such as three stripe damselfish, humbug dascyllus, or black and white damselfish. They only reach an adult size of 3-4 inches (7.6-10 cm). Sporting three broad black stripes on a white body, the humbug damselfish has a zebra like appearance. The stripes run slightly off vertical through the eyes and mouth, midbody and bisecting the caudal peduncle, making it half black and half white. 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 humbug 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.
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.
Coral reefs for the most part appear to be static environments, despite the presence of ever busy fish life, that is because most of the activities happening within corals are invisible to our eyes. In fact, coral reefs are a dynamic environment where every cm2 may hide beauty or a fight for survival! Among the invisible, corals are surely the most active, by building the amazing structure which allow us to see paradise tropical islands! However, they are continuously fighting for the survival, against predators, disease and environmental changes, and even between them. They are supplied with microscopic needles and venomous tentacles to kill any other corals and ejecting their stomach to digest them. The battle-zones when two different corals are easy to spot, there is often a cleared band between the two where they’ve killed each other off. They use similar tactics when they are fighting off invading algae. On healthy reefs, corals can maintain their territory, often beating back and even killing various types of algae. Here you will notice the two types ….
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 90%. 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.
Corals have many “enemies” in nature, one of them is a mollusk and its name is Drupella cornus. This is a species of snail with small shells (no more than 5 cm) covered by tiny bumps. The shells can sometimes be brown or pinkish; depending on the algae that are growing on it. This species is usually common in living corals of the Indo-Pacific, where is frequently found hiding from predators in the crevices during the day. Drupella is considered a threat for corals since it eat live coral tissue by stripping the soft body from the coral skeleton. This species prefer to feed on fast-growing coral species such as Acropora or Pocillopora, but it can feed on massive coral species, such as Porites in absence of their favorite preys.
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.
Have you ever wondered why some corals are more colorful than others… That is because some corals increase the production of colourful protein pigments (such as these purple tips) when they are exposed to more intense sunlight and this colony, of a branching Acropora, is simply amazing. Scientist have found that these pink, blue and/or purple proteins act as sunscreens for the corals by removing substantial light components that might otherwise become harmful to the algae hosted in their tissue. Corals rely on these light-dependent miniature plants, the so-called zooxanthellae, since they provide a substantial amount of food. Furthermore, these tips consist of a particular polyp called an “apical polyp”. It is responsible of the growth of the particular branch. For instance, it will reproduce asexually by cloning itself, potentially an infinite number of times throughout its lifetime. Here and there, one of the “radial polyps” will differentiate becoming a new apical polyp with its distinguished purple color, driving the growth of a new branch.
Looking at your frame, you will see that it is doing great and the corals are doing fantastic and survived the heated months and some stormy weather with minor damage. We have done some recent maintenance on all the frames which include cleaning them, removing the invasive algae and coral predators to maximize growth. We also noticed a few dead and loose fragments, they have been removed and reattached to improve the growth of the fragments. 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.
One of our goals of this project is to increase the local biodiversity. Underwater artificial structures such as coral frames are usually colonized by different species of fish everyday. They may use the structures for shelter from predators or to feed. This orange-striped triggerfish, visiting your frame is an expert swimmer and are able to move horizontally, diagonally and even drift over the reef. Growing to about 30 cm (1 ft) in length, triggerfish have an unusual defense mechanism, they make pig-like grunting sounds when danger is near, they also have a strong spine on their back that erect if they feel threatened . Their strong teeth also allow them to eat tough food like mollusks and sea urchins.
