Could some coral be less vulnerable to ocean warming than previously thought? In a new article published in Nature Climate Change, scientists studied how increasing seawater temperatures could affect the growth of coral reefs off the coast of Central America, and found that the reefs closest to the coast were affected much less by rising ocean temperatures than reefs further out in the ocean.
Corals and Coral Reefs
Corals are small animals, living in colonies in marine waters; each element of the colony is called a polyp. Polyps secrete calcium carbonate (CaCO3), a solid compound, which forms a skeleton normally referred to as a coral reef.
Coral reefs are essential to the lives of corals; in fact they protect the polyps from predator species in the sea. Moreover, reefs are the home for algal species such as zooxanthellae. These, while hosted by the corals, perform photosynthesis; in this way, they generate energy and/or nutrients for the corals themselves, which allows them to exist.
Possible Threats to Coral Reefs
The health of corals, and consequently coral reefs, can be affected by several parameters. It was reported, for instance, that an increase of the acidity level of oceans’ waters, due to higher carbon dioxide (CO2) concentration, can have an effect on the calcification process.
Another issue that may affect the corals is the temperature of the water; a temperature increase of only 1.2 oC can have a negative impact, because the higher temperatures may cause coral bleaching, in which both the coral pigment and the zooxanthellaeare released into the water. Considering that the algal species are responsible for the photosynthesis that supports the reef, excessive bleaching can have very harmful consequences for the corals.
Research has shown that the Sea Surface Temperature (SST) has increased in the last 35 years; the increase can vary between 0.3 and 1 oC, depending on the area. Such higher temperatures may have affected the reefs.
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