The warming seas are cooking the coral (well actually, bleaching it)
|Healthy coral reefs support a mind-boggling variety of marine life.|
California’s rugged and scenic, wave-tossed coastline boasts extensive kelp beds and other riches, but is too far north to be blessed with coral reefs. However, they do flourish not far to the south along the Baja Peninsula in Mexico. And they also grace the Florida Keys, Hawaii and the U.S. Virgin islands.
But the world’s coral reef systems really come into their own in the Caribbean Sea and especially the South Pacific and Indian oceans. Australia’s 1,400 mile-long Great Barrier Reef is one of the natural wonders of the world; it can be seen from space and is the world’s largest single structure built by living organisms.
In terms of the wealth of abundant life and biodiversity they support – estimated at more than 1 million species – coral reefs have been dubbed the “rain forests” of the oceans.
Now all of that is under threat.
In a recent article, “The Oceans Are Becoming Too Hot for Coral, and Sooner than We Expected,” Ove Hoegh-Guldberg, Director of the Global Change Institute at the University of Queensland in Australia, writes that a massive, global “bleaching” event is now underway.|
The colorful, rigid and complex structures we think of as corals are actually the homes of the primitive, ancient animals (coral polyps, related taxonomically to jellyfish and sea anemones) that construct them with the assistance of algae called zooxanthellae, with which the corals enjoy a mutually beneficial or “symbiotic” relationship.
Coral polyps provide shelter, and the zooxanthellae provide food. Corals become bleached when they are stressed by changes in environmental conditions such as temperature, light or nutrients; then, they expel the symbiotic algae living in their tissues, causing them to lose color and turn completely white.
Corals can survive an individual bleaching event, but they are under greater stress (because they are slowly starving) and more vulnerable to mortality.
|Bleached coral is a ghostly, ghastly white.|
In 2005, the United States lost fully half of its coral reefs in the Caribbean in a single year due to a massive bleaching event. This was the same year that excessively warm surface temperatures in the Caribbean and Gulf of Mexico generated Hurricanes Katrina, Rita and Wilma, the last of which was the most intense tropical cyclone ever recorded in the Atlantic basin.
I snorkeled among the dead, skeletal elkhorn coral reefs of Buck Island Reef National Monument in the U.S. Virginia Islands a couple of years later. It was like visiting an underwater graveyard.
Soaring ocean surface temperatures associated with a major El Niño event in 1998 caused the first recorded global mass bleaching event. By the end of that year, up to 16 percent of the corals on the world’s tropical reefs had died.
Now, Hoegh-Guldberg writes that, in recent weeks, scientists have expressed concern that:
…super-warm conditions are building to a point where corals are severely threatened across the tropical Indian, Pacific and Atlantic oceans. They did so after seeing corals lose color across the three major ocean basins – a sign of a truly momentous global change.
This is only the third global bleaching event in recorded history.
Why the current bout of bleaching? Well, we are once again in an El Niño year, so much of the Pacific especially is abnormally warm. El Niño is a variable, periodic and naturally occurring phenomenon, formally known as the El Niño Southern Oscillation (ENSO), but like another entirely unrelated natural phenomenon – soil erosion – it is apparently being aggravated by human influences. Climate change has been pushing up average sea temperatures, and ENSO itself may be changing because of this.
It is quite plausible that in just several decades’ time the oceans will have simply gotten too hot – and too acidic – to support corals, and the million species and 500 million humans whose livelihoods depend on them.
Years ago, with a mask and snorkel, I first explored a coral reef on the Baja Peninsula, teeming with fish and dazzling with colors and shapes. It was otherworldly. I vividly remember feeling a sense of wonder, and also one of elation, that here was an ecosystem, unlike terrestrial ones, that was beyond the reach of man to muck with.
Alas, how wrong I was.