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.
Why are coral reefs so important? For once, coral reef are said to be one of the most diverse ecosystem on the planet and provide shelter and habitat for many marine organisms. Furthermore coral reefs take an integral part in nitrogen and carbon fixing and are a source of essential nutrients for the marine food web. But not just marine organisms benefit from coral reefs, they also play a crucial role in protecting the coastline from wave action, tropical storms and coastal erosion. Economically coral reefs are important to foster healthy and abounded fishing grounds, tourism as well as the creation of soil and solid substrate for construction.
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.
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.
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
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 80%. 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.
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.
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.
Look at this piece of coral fragment on your frame taken a few weeks after construction. You will see how it have already accumulated some unwelcoming algae. When doing maintenance on the coral frames we are removing any means of competition such as this, in order to benefit corals and their healthy growth. This is an example of what we call coral-algae competition. The red filamentous algae (pictured) may prevent the coral growth by competing for the space. The algae growth is much faster than coral growth, as such the algae usually wins the space. However, it may also happen that the coral use defense weapons to gain its space! Part of our work consists in removing algae or other organisms that may compete with corals for the space.
As you can see from your first post, we have already done the first maintenance on your frame which is to remove the cable ties and move the frame with the other frames in order to create a coral garden. Some information about the fragments that we put on your frame, all the fragments were collected in our house reef lagoon, these were all broken from the “mother colony” by weather, fish or human activities. All the pieces on your frame belong to the genus Acropora which is one of the fastest growing corals and almost 149 species described. Over the next few months we will show you some more really close-up pictures of the fragments with some interesting facts and the creatures that now live on your frame. After 6 months we will show you once again the progress of your frame in a new post.
