Temperature instability is considered the chief reason for coral bleaching. In natural reef, global warming is raising the temperature and leading to bleaching of corals.
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Zooxanthellae, which is the agent contributing to the various colorations in corals is expelled by the corals when it is stressed due to intense temperature or changed water conditions. Sometimes it is completely expelled which results in complete bleaching of the coral and sometimes partially reduced which is witnessed by slight discoloration in corals usually faded color or pale with some pigmentation.
The same occurs in an artificial reef tank where temperature, water conditions or any another factor might stress the coral resulting in bleaching. If the zooxanthella is by any means not supplied with proper conditions under which it undergoes photosynthesis, it will soon be expelled from the coral and lead to whitening of the coral. In a reef tank, this may happen due to various reasons:
1.Increased or reduced water temperature. Always use a good thermometer to keep a check in water temperature especially during water change and in whether change.
2.Change in salinity of water. It is important that you regularly keep testing the ph level of water.
3.Change in intensity of lights. Some corals thrive only in high intensity lights and hose are mostly observed to show bleaching signs when lights go dim.
4.Algal or bacterial infection. For example, Endolithic fungi. If the coral gets covered by algae, it is concealed from lights and hence no photosynthesis can take place.
5.Lack of nutrition.
6.Conflict from tank mates. If there is a conflict for turf in tank, one of the corals may get deprived of its necessary factors resulting in bleaching.
7.Chemicals – pollutants, metals, pesticides, contaminants.
8.Low water motion or stagnant water can also stress the corals to larger extent.
Understanding the factor that might have led to coral bleaching in your tank makes it easier for you to work on the recovery process. Though some corals when bleached completely refuse to recover to normal and you might have to suffer some loss, yet you can save many of them if you know what could have led to bleaching. For instance, if you know that the factor is lack of nutrients, you can work on feeding them well and with the food that is best for their thriving.
Whatever might be the reason behind coral bleaching, remember that it has left the corals stressed and that’s where you have to concentrate on. If you know the factor that stressed the corals, try best to eradicate them or better still, give the specimen the conditions that are best suited for its thriving. Each specimen has different demands and various food requirements. Learn on the species that is undergoing the stress and give them the best treatment.
Also pay heed that you must give them the kind of food that help to make up for the lack of food produced by the zooxanthellae. Even if you never target feed them, do it frequently till the corals have recovered. Perfect nutrition is the best way to help them recover and get back to the healthy and attractive hue they once had.
It is very difficult to determine if coral tissues are still remaining or lost. If there is expansion, you can be assured that there are still tissues and chances or recovery is present. But in some cases the tissues do not expand or remain contracted; it becomes difficult to assess if tissues are lost or present. One of the best ways to evaluate this is to observe for the rapid colonization of diatoms and other algae. These algae will not settle on coral tissue, but readily populate exposed skeleton and should be visible to the eye within a day or so after skeletal exposure.
Whether or not a coral will recover is hard to decide. But you must try to help them recover and you might get lucky to see some of the coral regaining coloration. However, also note that the discoloration of coral might also result due to tissue recession, competition, predation, environmental stress, and disease. It might not be necessarily bleaching if coral causing it to turn pale, but the way to help the corals out of these predicament is also the same.
