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.
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.
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.
A fresh scar from a broken branch, the white indicate the calcium skeleton underneath that is produced by the tiny polys above year after year. Since collected fragments are picked up rather than broken down from existing colonies they often have dead sections covered with overgrowing algae and dead or damaged polyps, as such these sections are removed for faster recovery. You can already see the new polyps starting to grow along the bottom of the scar, soon the branch will regrow into its former state.
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.
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.
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.
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 moderate signs of bleaching of around 40%. 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 between minor bleaching on the branching tips, surface bleaching (those directly exposed to the sun’s rays) and intermediate bleaching (still some symbiotic algae present but corals are pale in color).
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.
Coral growth is a process that takes a very long time since corals invest a lot of energy in building their calcium carbonate skeleton. Stony corals (or scleractinians) are the corals primarily responsible for laying the foundations of, and building up, the reef structures. Massive reef structures are formed when each individual stony coral organism—or polyp—secretes a skeleton of calcium carbonate. In this photo you can appreciate the growth of this Acropora digitifera, which after 18 months is beginning to fuse onto the metal frame.
Despite your frame growing so well there is sometimes some fragments that is not doing so well. As you can see from, some fragments such as this one pictured have some damage and as a result they can day of die off partially or in some cases completely. This happens from time to time that fragments might receive very high stress levels due to increased water temperatures and they lose the symbiotic algae Zooxanthellae that they need to survive. Sometimes corals also need to compete with invasive algae that grow over the polyps and 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 that many of the surrounding branches are still alive, they still have some nice color and even beautiful purple colors but if you look closely to the center where the branches attach, you will see that the skeleton have completely died and that the algae are now starting to cover it.
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.
The Coral Conservation Project main purpose is to educate and to show people what is a coral and how easy it is to help our coral reefs. We usually build the coral frames with our donors to make them an active part of this project. Unfortunately, for logistic reasons, we have to build the frame in the shoreline exposing the corals to the air. Usually corals can handle periods of air exposure pretty well, however some colonies might been already exposed to others stressors before the collection, for this reason more sensitive and they might not recover. Your frame has been done in November 2017 and unfortunately the colony on the top of the frame did not survived, for this reason we decided to remove the dead colony and to add some Acropora colonies.
