Contributed by Julie Freydlin the 12th of November, 2013, on a Tuesday brain coral that has been bleached NOAA A coral reef in the United States Virgin Islands that is in good health. NOAA Coral reefs throughout the world have been threatened with extinction over the past few decades as a direct result of rising ocean temperatures.
- On the other hand, the results of a recent research show that corals might be able to adjust to some of the warming that will occur.
- According to records of temperatures, the warming of ocean waters is thought to have begun not long after the industrial revolution, around around the turn of the 20th century.
In years that are unusually warm, the algae that live in corals and provide them with food begin to produce poisons. Corals depend on these algae for their nutrition. Corals expel algae from their tissues in an effort to shield themselves from the poisons, but this results in the corals losing their primary food supply.
According to Cheryl Logan, an assistant professor in the Division of Science and Environmental Policy at California State University at Monterey Bay and the lead author of the new study in Global Change Biology, corals “are under more stress and are subject to mortality” when they are not provided with nourishment.
When temperatures reach extremely high levels, a phenomenon known as bleaching takes place in which corals lose their algae and begin to turn white. According to Mark Eakin, one of the authors of the study and the director of the NOAA Coral Reef Watch monitoring program in College Park, Maryland, widespread bleaching was observed for the first time in 1982 and was caused by a spike in average summer temperatures caused by the El Nio cycle that year.
- This was the first time widespread bleaching had been observed.
- Researchers have determined, with the use of satellite data that was not readily available until the late 1980s, that corals in various regions of the world bleach, or reach temperatures that are higher than their “bleaching threshold,” at varying temperatures.
For example, corals that are found in warmer regions across the world have greater bleaching thresholds than corals that are found in cooler regions. But as a general rule, corals will begin to bleach anywhere between one and two degrees Celsius higher than the typical high temperature for the hottest month of the year in a given site.
According to Eakin, the amount of coral bleaching that has been observed in various parts of the world is proof that this threshold has not grown by a significant amount over the course of the past several decades. However, according to Eakin, the fact that corals have various bleaching thresholds in different areas demonstrates that corals are capable of adjusting their bleaching thresholds, which suggests that potentially corals might also adapt to rising temperatures within the same site.
The NOAA/GFDL Earth System Model 2 was utilized by Logan, Eakin, and their colleagues in order to put this idea to the test. The researchers predicted what the bleaching threshold was for the years 1900 to 1910 based on water temperature measurements that were available at the beginning of the previous century.
- According to Eakin, widespread bleaching episodes would have happened earlier than 1982 and would have been more extreme if that threshold had been maintained at its previous level.
- However, prior to 1982, such extensive bleaching was not observed elsewhere in the world, which the research team interpreted to mean that corals had adapted to at least part of the warming that had taken place.
They pointed out that this finding demonstrates that corals are capable of adapting, even if only partially. The increase in bleaching thresholds that is part of the adaptation, however, is not keeping up with the rate at which the planet is warming. According to Eakin, “we are witnessing a rise in the frequency and severity of the warm events that are driving corals to bleach.” “We are seeing an increase in the frequency and intensity of the warm events.” Because of this, a large number of corals are unable to prevent bleaching as a result of the warming that is occurring right now.
- The capacity of the corals to partially adapt is attributed by the researchers to a number of different causes.
- To begin, more heat-resistant corals are able to repopulate regions that have been deserted when corals that are more susceptible to heat perish.
- In addition, the algae that are expelled by corals are being replaced with algae that are more resistant to the effects of heat.
The scientists hypothesize, on the basis of these considerations, that a significant number of corals may be able to last until the end of this century, provided that the pace of warming experienced today is slowed down. But some academics who study coral reefs argue that even if global warming does slow down, corals would still be in danger.
Ruben van Hooidonk, a postdoctoral associate at the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) at the University of Miami and NOAA’s Atlantic Oceanographic and Meteorological Laboratory in Miami, who was not involved with the study, said that he arrived at a different conclusion after using an ensemble of climate models.
“When I used an ensemble of climate models, I came to a different conclusion,” he said. Even if there is a reduction in the rate of warming, “I calculated that roughly 90 percent of reefs” will suffer bleaching conditions yearly by the year 2070, he adds.
According to Eakin, one intriguing point to keep in mind is that although though the adaptation may make it possible for the corals to survive in temperatures that are rising, the adjustment also has unfavorable side effects. When only corals that can withstand high temperatures continue to thrive, biodiversity suffers.
In addition, the heat-resistant algae that replace the algae that were expelled grow more slowly, which results in a reduction in the amount of food available for corals. As a direct consequence of this, corals mature at a slower rate. In the meantime, the carbon dioxide that is emitted into the atmosphere reacts rapidly with the carbonate that is present in the water to produce carbonic acid, which results in the acidification of the ocean. 
What adaptations do coral have to survive?
There are corals that have adapted in such a way that they can withstand the coral bleaching. That is to say, they are defended by the elements on their own. They create something that’s similar to sunscreen and it’s called a fluorescent pigment. These pigments come together to form a shield around the zooxanthellae, which protects them from the potentially damaging effects of sunlight and ultraviolet radiation when the temperature is high.
What are some adaptations of plants in the coral reef?
Seagrasses have specialized roots that grow horizontally and stretch out in order for them to be able to endure the powerful waves of the ocean. When there are strong currents in the water, the roots of seagrass, which are known as rhizomes, help to keep the plant rooted in place so that it does not become dislodged and float away.
What factors affect coral development?
Within the broad limitations given by water chemistry, temperature, and solar radiation (see above), environmental elements that impact coral development also vary substantially across scales of kilometers to tens of kilometers, including but not limited to the following: the type and depth of the substratum, the temperature (Figure 2c), the climate of the waves, the salt of the water, the transparency of the water, and the nutritional content
