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.
What is biodiversity? Biodiversity is the variety of living species that can be found in a particular place, for instance the number of coral species on your coral frame. Coral reefs are said to have the highest biodiversity of any ecosystem on the planet—even more than a tropical rainforest. In this particular image you can see two species of the Acropora genus, one of the fastest growing species of coral. Since we collect broken fragments from the bottom and not original colonies, the biodiversity on the frames is often between 1 and 4 species of corals, depending on location of collection. You will see that these small pieces have already grown quite a bit in the one year since construction. Of course we always try to keep the diversity high between all of the frames and during maintenance we often add new pieces onto the frame. Hopefully soon we will see lots of different marine species occupying your frame, which is the goal of our Coral Conservation Project.
Look what we found hiding in one of the corals on your frame. This is a red coral crab (Trapezia cymodoce), a small and necessary symbiont of living branching hard corals such as Acropora corals (Acropora sp.) and Cauliflower corals (Pocillopora sp.). They are well hidden and quick, and thus hard to spot and photograph. They have a small flat body, no wider than 1cm with pointed pincers in the front and can vary from red to dark orange. Within these corals, they receive needed protection from predation and also feed on the mucus that is produced by hard coral; this they gather with minute comb-like structures on the tips of their feet. In return, the coral gets a cleaner of excess sediment and also a guardian to fend of coral predators such as Crown-of-Thorns starfish by nipping the sensitive tube feet of the starfish. Usually in one coral colony you can find a pair of male and female with the latter being larger and the males having claws that are proportionally larger. These crabs are definitely worth having around on your frame
Just look at this amazing creature that lives on your frame, there are actually two of them is you look closely. These are Christmas tree worms (Spirobranchus giganteus), a species that belongs to the tube-building polychaete worms. Its name refers to the two chromatically hued spiral structures that we can see here in the image. These multicolored spirals are highly modified structures for feeding and respiration and can also be various colors. They are known to occur throughout tropical oceans and commonly found embedded entirely in heads of massive corals, such as stony and brain corals but not unusual to find them in Acropora corals such as these. Similar to other members of this family, they secrete a calcareous tube around its body which serves as protection. When danger is close, they will retract into these tubes and only come out again after a few minutes. These worms luckily didn’t seem to mind that I was taking this beautiful picture of them
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 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 through 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 reason (i.e. high temperature) one of the two parts is not working properly the process stops and the coral may die.
This is your 6 month frame progress update. Your frame is doing fantastic!
Looking at your frame, we can see lots of new growth, especially of the acropora corals (the branching & fast growing corals). We can see some of the corals are competing for space, which is a good problem to have, it means your frame is thriving. We can also see that your frame is contributing to the overall health of the coral ecosystem. We see lots of life such as little fish, crabs, worms and mollusks around your frame. Overall your frame has survived the warm months of March, April and May just fine, unfortunately some of the other frames in our colony weren’t so lucky.
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 ….
Here, we are excited to tell you about this nice colony living on your frame, the species is Pocillopora verrucosa, also known as cauliflower corals. They are usually cream, brown or pink, sometimes blue in color and have a widespread distribution within the Indo-West Pacific and Eastern Tropical Pacific regions. Colonies may grow up to 30 cm in diameter, their branches are medium sized and are covered with uniform verrucae (little bumps). This species is typically found in shallow water from exposed reef fronts to protected fringing reefs. They are also home to species of smaller fish that finds refuge within the healthy branches of these corals. You will also see some small fish hiding inside the coral, they are known as humbug damselfish and can often be found hiding inside the branches of these coral species
Look between the bars of your frame and you will spot a very bright and yellow visitor, common around the reef and also around the frames. This is known as a Black Saddled Butterflyfish (Chaetodon falcula). The name of the genus comes from the Greek “chaite” = hair and “odous” = tooth, referring to their “bristle-shaped teeth” and their species name “falcula” means “falcetto” in Latin and refers to the pointed dorsal spots that have the profile of a small sickle. This is a medium-sized perciforme which belongs to the Chaetodontidae family; it is endemic throughout the Indian Ocean and here in the Maldives. In nature it is an almost exclusively carnivorous fish and feeds mainly on small crustaceans, polychaetes worms, annelids and tunicates. We can see these fish moving around the frames quite often and they help keep them clean from harmful predators. They really are a beautiful addition to the frames and also nice to see them coming back to see what they can find around.
Just look at this amazing creature that lives on your frame, there are actually two of them is you look closely. These are Christmas tree worms (Spirobranchus giganteus), a species that belongs to the tube-building polychaete worms. Its name refers to the two chromatically hued spiral structures that we can see here in the image. These multicolored spirals are highly modified structures for feeding and respiration and can also be various colors. They are known to occur throughout tropical oceans and commonly found embedded entirely in heads of massive corals, such as stony and brain corals but not unusual to find them in Acropora corals such as these. Similar to other members of this family, they secrete a calcareous tube around its body which serves as protection. When danger is close, they will retract into these tubes and only come out again after a few minutes. These worms luckily didn’t seem to mind that I was taking this beautiful picture of them
As you can see from the picture, this particular dead fragments 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.), it is very common in the Indo-Pacific area; but don’t worry, it’s not a threat for corals, they can live together in peace, however when they increase their biodiversity on the frames they are removed to minimize competition with corals. Ascidia is a filter-feeder, this means that it filters water looking for plankton to feed itself. The green color is given by some little green 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. In this particular case the fragment below may have died due to some high temperatures or other stress factors and algae started to cover the surface. On the plus side, look in the middle you will see a new addition to your frame, a baby coral which have settled on your frame. We will continue to monitor your frame, and remove the unnecessary and competing algae that competes with corals
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.
Do you know that even under the water we can found cobwebs? The responsible invertebrate responsible for this mesh is not a spider, but rather a gastropod mollusk called Ceraesignum maximum. As all Vermeidae, this mollusk species is sessile and houses themselves within tubular shells. They are common dwellers of shallow water in coral reefs and rocky shores. These nets are called mucus nets that can be expand around the individual up to 10 cm in diameter. Under wave action and currents allow suspended particles to be trapped in these sticky nets that are withdrawn at regular intervals for consumption.
