Thursday, February 02, 2006

Coral Bleaching



Many of us know and understand that corals are animals, they grow, feed, metabolize, etc. And they also have a symbiosis with microalgae, known as zooxanthellae. This algae undergoes photosynthesis and its byproducts (sugars, etc) are used by the corals. While there are species of corals without endosymbionts, many species cannot survive without these zooxanthellae. This is problematic because many reefs around the world experience patches of what is known as bleaching. This is when the coral expels the zooxanthellae from its body due to a number of anthropogenic or natural causes. Some events are not very severe and the coral can regains its zooxanthellae population, but some events are so severe that the corals die off and cannot come back.

There are numerous causes for bleaching events, including rising sea temperatures, increased solar irradiance, increases sedimentation, freshwater inputs, etc. Many human induced impacts include overexploitation and disturbance, increased sedimentation, nutrient overloading and global warming. Natural events include those such as ENSO (El Nino Southern oscillation), violent storms, and predation. Whatever the cause, corals bleaching creates major problems. If the event is severe and the corals cannot regrow, it can have devastating impacts on the ecosystem.

Some researchers believe that bleaching is an adaptive measure. If corals can expel the zooxanthellae that can't survive in the new conditions, perhaps they can obtain zooxanthellae that can (since there are multiple species of zooanthellae). Since different zooxanthellae have different tolerances to temperature, light and salinity, corals that expel one type during an event may be colonized by a new type, allowing the symbiosis to continue. While I know there has been work with this in a laboratory setting (although of course I cannot find the paper right now), how it plays out in the real world is another question.

Can we allow coral bleaching to continue in hopes it is just an adaptive measure? No. Major events are occurring every day. A devastating event is happening in Australia right now, off of the Queensland coast. Researchers are saying that the readings they are getting right now are similar to those experienced in 2001-2002 when the last major event took place, bleaching approximately 70% of the Great Barrier Reef. They think that this event can be similar. The article goes on to say that credible predictions for the entire GBR to be wiped out is 30 years, with the most optimistic predictions at 70 years.

It is absolutely incredible that so much information is out there, attributing so much devastation to global warming and yet our government does not seem to care. They are running on the platform that the end is near, the apocalypse is approaching so we might as well use all the resources we can (that was actually Reagan's position, his secretary of the interior stated almost those exact words, and I am quite sure Bush agrees whole heartedly). This can't all fall on the Republicans, afterall, Clinton was the one who failed to sign the Kyoto treaty to try to cut greenhouse gases by the year 2012. It is truly unfortunate that my kids may never be able to dive on a live coral reef and that apparently half the nation at least doesn't care. We can only hope that the more research that is conducted, like the new Census on Marine Life, a massive research initiative with over 70 participating nations, can generate enough data and awareness that people have to pay attention. Otherwise, I am moving to the moon.

1 comment:

Tait said...

actually, as far as I am aware, the Clinton administration, against congress' wishes, signed the Kyoto treaty on Nov 12, 1998 (At the behest of Al Gore who wanted to use environmental policy as his main stance in his upcoming run for office)...Bush backed the US out of the treaty as one his first initiatives as President...so I think its safe to put most of the blame on Republican shoulders...Democrats are not blameless for sure....but as far as tendancies towards environmental reform, the Democrats are light years ahead of the "religiuos right" republicans