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.
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 fun looking creature is indeed a sea snail. You might wonder where its house is … it is hidden below its black/ dark blue velvety mantle that makes this nail look more like a slug or a nudibranch. Underwater the sea snail (Coriocell hibyae) is often difficult to spot and resembles more a sponge than a moving animal. This snail is known from the Maldives, but might be found throughout the Indian Ocean (not much is known about its true distribution).
This species can reach a maximum size of 10 cm in length and it has five digit-like protrusions on its dorsal side. The body coloration varies from slate-blue to dark brown, with some small round black spots which are part of what makes it look like a sponge. A fragile ear-shaped shell is hidden inside the fleshy mantle.
This little snail prefers water temperatures of (23°C – 27°C) and mainly feeds on sea squirts (Didendum molle) which can also be found on your frame.
Have you ever wondered how do corals grow bigger or how their branches are getting longer? Coral reefs are mainly built by stony or hard corals, together with their endosymbiotic algae (algae living in the corals), zooxanthellae. To give you some information on how the calcification process works. The main elements needed to build the skeleton are Ca2+ (Calcium ions) and DIC (Dissolved Inorganic Carbon). Both of these elements are transported into a specific area of the coral called the “calcifying region”, which is situated under each single polyp. Here, the calcium carbonate (CaCO3) is formed throughout a chemical reaction. Finally, the calcium carbonate (or technically crystals of aragonite) is deposited to form the skeleton. The process involves the polyp’s cells and the Zooxanthellae, and by the mutualistic work of these two counterparts the skeleton is formed. However, if for any reasons (i.e. high temperature) one of the two parts is not working properly the process stops and the coral may die.
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).
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.
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.
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 minor signs of bleaching of around 20%. 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, surface bleaching (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.
Relationships with beneficial consequences between different species such as mutualism or commensalism are common in the coral reefs. In this photo, we would like to show you an important association that has been recently discovered by the team of researchers from the University of Milan-Bicocca. It refers to tiny hairy-looking animals living on the surface of corals called Hydrozoans belonging to the genus Zanclea. Indeed, it seems that they have an important role for the protection of the corals since they also have powerful toxin that may represent a strong defense against predators.
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.
Humans get a sun tan – corals become more colourful.
Here we would like to give some information about this nice looking Pocillopora meandrina branches collected from a broken colony that is located on your coral frame. They are also known as the cauliflower coral and are quite common around the Maldives. Pocillopora meandrina occurs on shallow reefs and amongst coral communities on rocky reefs, at depth from 3-27 m and their radiating branches can reach up to 40 cm in diameter. In this species many or most of the branches are flattened on the ends and some may be curved and their colors may vary from cream, green or pink. Pocilloporid corals, not excluding P. meandrina, are generally amongst the strongest coral competitors with relatively high rates of calcification. However, coral species exhibiting high rates of calcification usually have relatively high mortality rates
As you know we use plastic cable ties to attach fragments of corals to the iron bar structure which is very important for stability is necessary for corals to grow. The branching Acropora living on your frame is slowly growing over the cable tie. You can see part of the light-brown skeleton partially covering the two cable ties. In fact, it will be part of its skeleton forever. Plastic cable ties are a good compromise for attaching corals to the structure, since material is cheap, resistant and the results are great. However, we are following the upcoming researches to improve our technique in order to reduce the use of plastic.
Here you will see the first view of your frame, you will notice that all the plastic ties used to attach the fragments have been cut off. Some information about the fragments on your frame, most of them belong to the genus Acropora, which is a large and diverse group of hard corals with nearly 149 species described. However, we also attached some fragments that belong to Pocillopora genus. Both, these are well known to have a fast growth rate, between 13 and 15 cm every year. Your coral frame is now grouped with other very new frames by the Watervilla Restaurant in order to create a nice coral nursery. We will keep monitoring the colonies and updating you on the status of your corals! Thank you for supporting this project!
