Coral reefs are important ocean ecosystems. The provide a number of important functions, including acting as nurseries for a great number of ocean species. However, the health and viability of the world’s coral reefs has become an issue of increasing concern among world scientists. It is known that when ocean waters in which corals live surpasses its summer mean by 0.5⁰ to 1.5⁰ C, due to either ocean acidification or global warming, the corals become stressed, a phenomena known as coral bleaching. When corals become bleached, they die, and this can lead to a degraded reef system that can take millennia to rebuild. At the current rate of deterioration, it is estimated that stony corals, the ones that take the longest time to grow, may not dominate the reefs by as early as 2100. As these are important components to the coral reef ecosystem, there is a great deal of concern as to how this will affect the reefs and the organisms they support. Since many commercially important fish begin life in coral reefs, the loss of these ecosystems could also have a very negative impact on commercial fisheries.
Scientists have been looking for solutions as to how to best preserve coral reef species in order to preserve the coral reef gene pool. One of the most viable solutions is to transplant coral species to reef refuges, or areas which are not affected by ocean acidification or global warming. The researchers for this article (Fine, Gilder and Gen In, 2013) believe that they have found a solution in the Red Sea.
The Red Sea is a part of the Gulf of Aqaba. Over the past 30 years, as coral bleaching has been documented throughout the world, this region has been only moderately affected and the Red Sea itself has remained relatively unaffected. Scientists believe this may be the case for several reasons, including its recent geological history as well as its oceanography, topography and latitudinal location. In their study, researchers Fine, Gilder and Gen In present their hypothesis as to why the coral reefs of the Gulf of Aqaba do not follow the bleaching rule. Their research has led them to believe that over the past few millennia a selection process has occurred at the straits of Bab el Mandeb (the southern Red Sea) and the southern Red Sea, leading to a favoring of thermally resistant coral genomes. When these thermally resistant corals migrate and disperse north into the cooler waters of the Gulf of Aqaba, they are living in water conditions that are much below their bleaching threshold.
To test their hypothesis, the researchers conducted a study at the Interuniversity Institute for Marine Science at the Red Sea in Israel. They chose five five common coral species that live in the Red Sea, all known to bleach in Indo-Pacific reefs: the branching Stylophora pistillata, Pocillopora damicornis, and Acropora eurystoma and the massive Favia favus and Porites sp. Their goal was to see if these specific organisms had evolved a lower sensitivity to high temperatures due to living in the warmer waters of the Red Sea.
The researchers conducted their study over the course of one year, treating the corals to waters of varying temperatures, reaching a maximum of 34⁰C, a full 7⁰ above the normal high mean. The studies revealed that the corals were extremely resilient; none of the species showed any visual signs of coral bleaching, even though mass bleaching conditions are generally formed at +1.5–2 °C above the average summer mean temperature.
From these results, the researchers found that the coral species inhabiting the Red Sea and indeed the Gulf of Aqaba do not follow the global bleaching rule as it is currently defined. They believe that these corals have developed some sort of genetic trait that allows them to live at temperature ranges well above the normal mean. However, this will need to be validated by future genetic research. This study provides vital information as to coral ecology and can be useful in creating management strategies that will help to preserve coral reefs into the future.
- Fine, Maoz, Gilder, Hezi, and Gen In, Amatz Ia. “A Coral Reef Refuge in the Red Sea” Global Change Biology 7 Aug. 2013 3640-3647.