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The Andaman Sea, in the northeastern corner of the Indian Ocean, is by all accounts too warm for coral to thrive. Yet, researchers have found an incredible diversity of coral in the warm murky waters. The discovery, they say, offers hope that at least some species may survive global warming, eventually repopulating reefs now threatened by increasing ocean temperatures."The existence of so many novel coral symbioses thriving in a place that is too warm for most corals," Todd LaJeunesse, an assistant professor of biology at Penn State, explained, "gives us hope that coral reefs and the ecosystems they support may persist—at least in some places—in the face of global warming."
Coral, which is formed via a symbiotic relationship between algae, is highly sensitive to changes in light and temperature. When the surface temperature of the ocean gets warmer or colder by even a few degrees, massive bleaching—a sign of coral death—can occur. Such events have already taken place at some of the world's most spectacular reefs.
One algae species, Symbiodinium trenchi, is a generalist—able to bond with a variety of hosts. Though the algae is typically present in small numbers throughout the reefs of the world, it's high tolerance to variable temperatures has allowed it to dominate in the warm Andaman Sea. LaJeunesse commented that he had seen the species proliferate once before: In Florida, after a warm-current bleaching event devastated the reefs there.
Symbiodinium trenchi, which normally occurs in very low numbers in the Caribbean, was able to take advantage of the warming event and become more prolific because of its apparent tolerance of high temperatures...the species appears to have saved certain colonies of coral from the damaging effects of unusually warm water.
However, even this resilient species is not immune to the effects of global warming. If the temperatures in the Andaman Sea—which is typically as much as four degrees warmer than the rest of the Indian Ocean—increase much more, Symbiodinium trenchi, too, will die off.
The hope, then, is that Symbiodinium trenchi will be able to migrate away from its current home to repopulate areas now dominated by more sensitive species. When asked about "seeding" threatened reefs with more resilient algae, LaJeunesse was cautionary. He commented that "you never know what the effects might be of introducing an organism into an ecosystem in which it is not well established."
In addition, he said, most symbiotes are too closely tied to the existing coral algae. Symbiodinium trenchi may be able to keep a reef alive, but the result would be a much different ecosystem then we know today.
Read more about coral:
Florida Cold Snap Devastating Coral and Marine Life
Coral Can Recover from Climate Change Damage... In Marine Reserves
Dying Coral Reefs to be Frozen, Preserved for the Future
Coral Bleaching Creates a Vicious Cycle of Further Bleaching and Disease
6 Steps to Saving the World's Coral Reefs