This is a guest post by Nature Middle East writer Louise Sarant.
Some 70 million years ago, Africa and Arabia parted to give birth to the Red Sea valley – a thriving, yet highly stressful environment for the thousands species of corals, fish and macrophytes which inhabit its waters.
The Red Sea’s salinity is currently at 40 parts per thousand; in simple terms, that’s 40 Kg of salt for every 1000 litres of water, substantially higher than the Mediterranean Sea’s 35 parts per thousand.
The water temperature of the Red Sea also ranks among the highest in the world and is believed to warm faster than the world average, according to a study by the King Abdullah University of Science and Technology (KAUST) in 2011. The researchers found that the Red Sea waters have warmed by up by to 0.7°C since 1994, in contrast to the global ocean temperatures which rose by 0.5°C.
The water’s high salinity and temperature have created a difficult environment for its biota, particularly for its plentiful coral reefs. But against all odds, they seem to be faring better in light of climate change than other corals worldwide. They continue to build extensive reef systems up and down the Red Sea’s coasts, somehow adapting to those harsh conditions.
“If you were to take a coral from the Great Barrier Reef today and drop it into the Red Sea, I would be surprised if that coral lasted a month,” says Michael Berumen, a marine biologist at KAUST.
This does not mean that the Red Sea corals are and will be immune to the various expected climate change impacts.
“While there is no such thing as an unimpacted ecosystem today, the Red Sea is still considered a thriving ecosystem,” says Gustav Paulay, marine invertebrate curator at the Florida Museum of Nature History. “There is bleaching and there is mortality, but when you dive in the Red Sea you don’t lament not being there a couple decades ago.”
Berumen is convinced the Red Sea will eventually bear the brunt of climate change, but it has a remarkable advantage. “What matters here is the starting point, the relative difference between the Red Sea and other reefs living in different conditions.”
Right now, marine biologists are trying to figure out what are the ecological or genetic mechanisms that allow Red Sea corals to survive in harsh conditions that corals in Australia, the Maldives or the Seychelles cannot withstand.
“Because the Red Sea is already so much warmer, it is possible that what we are looking at now are the conditions in which reefs in other parts of the world will have to deal with in the not too distant future,” says Berumen.
Understanding the adaptation mechanisms and higher tolerance of the Red Sea corals could change conservation mechanisms of corals worldwide.
Scientists have identified a few conditions which partly explain the resilience of Red Sea corals. “There are very little runoffs, coupled with a very low population density,” says Paulay, who adds that with the very few service runoffs, the pollution does not get very far into the sea.
Since the Red Sea is already warm, a small rise in temperature would be significant but manageable. The Red Sea is low on nutrients and offers little to sustain life. This has forced Red Sea species to find survival strategies, so they end up being sturdier and more resistant. Paulay also views the complex political situation in most coastal countries around the Red Sea as a protective measure. “If people are not letting other people go there, then nature is protected,” he says.
According to Paulay, corals can adapt to gradual change in temperature, but the problem with global warming is that the change is too fast.
Deep-sea corals in the Red Sea, which live in depths between 200 and 800 m, have adapted to warmer waters by reducing their living surface area which in turn limits their metabolic requirements.
Berumen explains that you can occasionally see similar responses with shallow water corals, which can sacrifice 90% of their colony and focus on a single small area, hoping to survive.
“These animals are far more complex and capable than most people give them credit for, and we have a lot left to learn,” concludes Berumen.
Check out Nature Middle East‘s special series on the curious case of Middle East’s coral reefs here.
Image credit: Tane Sinclair-Taylor/ Red Sea Research Center/ KAUST