Coral reef bleaching, which is the whitening of diverse invertebrate taxa. The cause of the whitening is “from the loss of symbiotic zooxanthellae and/or a reduction in photosynthetic pigment concentrations in zooxanthellae residing within the gastrodermal tissues of host animals. ” (P. W. Glynn) The reason why coral reef bleaching is such a concern is because the “consequences of bleaching large numbers of reef-building scleractinian corals and hydrocorals. “(P. W. Glynn)
Sunscreen causes coral bleaching by promoting viral infections. The goal of this experiment was to see how sunblock ingredients have an impact on hard coral and their symbiotic algae. The experiments were conducted in many different tropical regions for example the Atlantic, Red Sea, Indian, and Pacific oceans by supplementing coral branches with aliquots of sunscreens and common UV filters contained in sunblock formula. Zooxanthellae were checked for viral infection by transmission electron microscopy analyses and epifluorescence.
Sunblock does cause the rapid and complete bleaching of hard coral, even when it’s at extremely low concentrations. The effect of sunblock is due to organic UV filters, which are able to activate the lytic viral cycle in symbiotic zooxanthellae with latent infections. In the end sunblock, by promoting viral infection, it will most likely play an important role in coral bleaching in areas prone to high levels of recreational used by humans. Danovaro, Roberto, et al)Sunblock is not waterproof, even though it’s promoted as such. Massive amounts of people enter the ocean every year having the sunblock come off, which then travels through the water. Therefore the coral ends up poisoned.
Coral Reef Bleaching (stress) Bleaching or paling of zooxanthellate invertebrates occurs when either the densities of zooxanthellae decline and or the concentration of photosynthetic pigments within the zooxanthellae falls. Buchheim, Jason) So if the stress of the bleaching isn’t severe and it decreases as time goes on then the coral is more likely to gain back their symbiotic algae within several weeks or a few months before it’s back to normal. If the stress continues then the zooxanthellae populations will not recover and that ends with the coral host dying. Since the bleaching is occur by stress, it can be induced by many different factors, either alone or together.
With this being known it is difficult to clearly classify the cause for the bleaching that is happening to the coral. Buchheim, Jason) Some of the stressor that have been known for the coral reef bleaching are temperature, solar irradiance, subaerial exposure, sedimentation, freshwater dilution, inorganic nutrient, xenobiotic, and finally epizootics. Temperature is known for stressing the coral because the coral lives in a narrow temperature margin, so when the temperature of the water either drops or increases it will induce the coral bleaching. Solar irradiance is known for causing the stress during the summer months and in coral that lives in shallow water.
Both photosynthetically active radiation and ultraviolet radiation are known for causing the bleaching. Subaerial exposure causing bleaching by sudden exposure to the reef flat coral to the atmosphere for example when there are extremely low tides. The sea level dropping or tectonic uplift can induce the bleaching. With sedimentation there has been very few time that the bleaching is completely linked to sediment but it is possible, it has not been tested yet to actually see if sediment loading could make zooxanthellae species more likely to cause bleaching.
Freshwater dilution causings bleaching by the active dilution of reef water from storms and runoffs are known for the bleaching that is caused. Even though inorganic nutrients do not cause bleaching but the increase of the nutrients actually increases zooxanthellae densities two to three times, because of this it lowers the coral resistance and gives it a greater ability to adapt diseases then coral that do not have this.
Xeno results in bleaching because zooxanthellae loss happens when coral is exposed to elevated concentration of many different chemical contaminants. Epizootics are pathogens that induced the bleaching but in a different way, instead of patchy or whole colony death and sloughing of white tissues causing a white skeleton but some of these pathogens have been identified the cause of translucent white tissues, which is a protozoan.
All of these things have been identified of causing the bleaching or are responsible for it. Buchheim, Jason) Coral reef bleaching and global climate change: Can corals survive the next century? “Coral reef ecosystems are threatened on a worldwide basis, with overfishing, diseases, eutrophication, hurricanes, overpopulation, and global climate change all contributing to recent declines in reef-forming corals” (Michael P. Lesser) The principal region of the study was based in the eastern Caribbean which was found to have the highest stress level for the coral with the coral being bleached.
Donner et al conducted the research which showed the contribution of human induced climate change for causing the most coral reef bleaching event on record, the Caribbean coral bleaching in 2005. As the study went on it showed that in the 1970s it started to increase in sea surface temperature (SST). (Hoegh-Guldberg, Ove) Data has shown that there is no historical record of similar SST that goes with the warming of the caribbean and how much the coral were being bleached.
The highest DHM for the study in the caribbean was 3. 2 CO in 2005. Events similar to what happened in 2005 are very unlikely to happen again without anthropogenic forcing, but it also shows that with it is that the event in 2005 is a 50 to 500 year event or interannual climate variability can change how fast the occurrence of another 2005 event to happen in 10 to 70 years. (Hoegh-Guldberg, Ove) Donner et al also conducted the simulation under two different events and they both showed that the stress on the coral will go over the DHM values that happened in 2005 to happen in 2100.
It could also be as little as 20 to 30 years for bleaching to really take affect. Donner et al throws in another factor that the coral could have “the potential for the algal symbionts of corals to acclimatize or adapt by increasing their thermal tolerance by 1. 0-1. 5°C. If an increase of 1. 0°C in thermal tolerance is acquired, the occurrence of DHMs >2. 0°C-months every 5 years could be delayed until the 2040s or even 2050s, and an increase in thermal tolerance of 1. 5°C would further delay DHMs of >2. 0°C-months every 5 years until the 2050s or 2060s” (HoeghGuldberg, Ove).
Other factors that could change these prediction include both visible and UV portion of the solar spectrum that could affect the stress on the coral which will lead to the bleaching of the coral. Coral reef bleaching is caused by many things but for the most part it is because of humans. With the global climate changing so are the coral like many other things and sadly they are dying off because of the temperature changing. Which is causing coral reef bleaching which is when the whitening of diverse invertebrate taxa it is caused by when zooxanthellae decline and or the concentration of photosynthetic pigments within the zooxanthellae falls.
