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).
Do you know that even under the water we can find cobwebs? The 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 expand around the individual up to 10 cm in diameter. Waves and currents fill the net with tiny particles. After a few hours the mollusk will inhale the net with all of its yummy goods caught inside.
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
The Chevron Butterflyfish Chaetodon trifascialis is a handsome fish known and named for its beautiful diagonal chevron design. It is one of the more elongate butterflyfish in the genus. Yet it is moderate in size, reaching a total length of only about 7 inches (18 cm). This is a striking species with its elegant form, graceful swimming movement, and alluring colors.
This fish is quite active and will swim freely in the open water, but it also spends time hiding in cracks and crevices where it will lie motionless. The butterflyfish likes table corals where it can hide, it is also fond of coral polyps, considered to be a delicatessen in the fish world. This species is a somewhat aggressive fish, it is territorial and can be aggressive towards other members of its own kind, and sometimes other butterflyfish.
Have you ever wondered how corals are eating and defending themself… here you will see some small extensions/tentacles protruding from each of the polyp housings. They are referred to as the defensive/offensive stinging mechanisms similar to sweeper tentacles and are often linked to their feeding and defending. Inside each of the polyps are the small animal that look similar to an upside-down jellyfish with tentacles that surrounds the mouth part, depending on the coral species, the amount of tentacles may vary. They will move around to collect anything that passes around in the water, usually small plankton where after they will maneuver it towards their mouth where the food will digested and passed down. These tentacles are also used for defending themselves against predators such as the coral eating snail, Drupella sp or the invasive Crown of Thorns Starfish. They also keep the smaller predators such as crabs or invertebrates away. These tentacles are seldom seen but do come out when they are feeling threatened or when they are feeding.
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.
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.
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 70%. 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 range 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.
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.
Looking at this species of Acropora on your frame, you will notice the white tips on the branches. When corals are stressed by changes in water conditions such as temperature, light intensity, or nutrients, they expel the symbiotic algae called Zooxanthellae, living inside their tissues, causing them to turn completely white, this is also known as coral bleaching. When a coral bleaches, it is not dead yet, but may soon starve if conditions persist, since the animals inside rely on this algae for its energy. If their stress levels are not severe, corals may recover. If the algae loss is prolonged and the stress continues, coral eventually dies. Here in the Maldives, the peak temperature is around March – June, when we also see some of the corals turn white, usually their colors return soon after if conditions don’t persist.
Coral reefs for the most part appear to be static environments, despite the presence of ever busy fish, this 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 which may try to steal space and light! Here you will see one species of Acropora on the side of the frame and in the top corner another species, these will soon start growing over into other space and only the winner will have the right of growing freely
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 into 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 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.
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.
Corals are marine animals with many surprises. In this photo you can appreciate two types of ecological relationships. The first is made by corals and a small simple organism called Hydrozoan (white hairy organism on the surface of the corals). Hydrozoans, belong to the genus Zanclea, and have powerful toxins that defend corals from predators. The other example is made by the commensal Hermit crab (in the background) that are opportunistic crustaceans living in any kind of ‘shell’ it would fit in, mostly mollusk shells. They are scavengers and may feed on whatever they find, helping the corals to stay clean from small organic particles and small algae.