By: Hannah Kish
Did you know that corals can have an immune response to damage and disease? This is especially important when trying to understand how corals can recover in a degrading reef environment. Coral recovery from things as common as physical abrasions are currently being studied. In the past year, publications addressing certain stressors in connection with the biological process involved have been released.
The simplest healing process to address is also the most common, physical damage. This is caused by a variety of things: entangled fishing lines around coral, recreational boating and diving, storms, natural predation, etc. The mechanisms of physical damage recovery are the most well-studied and understood, however, the relationship between the molecular and immune response is less clear. When a coral gets wounded there is an immediate response from their immune system. It causes the new lesions to clot, which then activates cells from the immune cells to be dispatched to the area of the wound. These cells begin to kill any bacteria that could potentially cause a disease or infection. In the third phase, these immune cells multiply to reform the layer of tissue injured. This all occurs in the first 48 hours most of the time and it is very similar to more complex species. This process has been documented and known for a few years, most recently documented are the, particular hormones that are produced when a coral is injured. The study focused on a species of Acropora found in the Pacific Ocean. Effects of injuries, both human-caused and from natural predation, were studied for up to 10 days after the occurrence of an injury. The scientists found hormones called tranglutaminase, melanin, and AMP were produced as a response. These hormones helped in the coagulation process and prevented harmful cells that could induce disease. More importantly, the process worked in the same fashion as higher level species. This means that the immune response of corals may be a lot more intricate and complex than what the simplicity of the structure would suggest.
Physical damage is not the only variable in coral decline the past few decades however. Ocean temperatures have steadily increased in the last fifty years and pose major problems to the reef ecosystem. In regards to physical damage, the rising of ocean temperatures has a strange effect on the production of the hormones and so with the healing process of wounds. It was found that depending on the specific hormone, the level of production either increased or decreased. One can imagine what the changing of these levels could have on the overall healing process. It was found that if a coral was partially bleached, it healed at a slower rate than a healthy coral. For a coral that was fully bleached, the healing process was stopped all together and no recovery of tissue occurred. With both occurrences, the opportunity for other problems to arise increases, such as a decline in structural integrity, more disease, and less ability to reproduce.
Pinzon, J. H., B. Kamel, C. A. Burge, C. D. Harvell, M. Medina, E. Weil, and L. D. Mydlarz. “Whole Transcriptome Analysis Reveals Changes in Expression of Immune-related Genes during and after Bleaching in a Reef-building Coral.” Royal Society Open Science 2.4 (2015): 140214. The Royal Society Open Science. The Royal Society Publishing, 1 Apr. 2015. Aug. 22 Mar. 2016.
Van Der Water, Jeroen. “Elevated Seawater Temperatures Have a Limited Impact on the Coral Immune Response following Physical Damage.” KLN PASS User Login. Hydrobiologia, 17 Mar. 2015. Web. 23 Aug. 2016.
Van Der Water, Jeroen, Tracy D. Ainsworth, William Leggat, David G. Bourne, Bette L. Willis, and Madeleine J. H. Van Oppen. “The Coral Immune Response Facilitates Protection against Microbes during Tissue Regeneration.” Molecular Ecology Mol Ecol 24.13 (2015): 3390-404. 1 July 2015. Web. 22 Aug. 2016.