Thursday, December 13, 2007

"Evolution in Reverse"

The decrease in ocean alkalinity is a biological concern. The oceans have become more acidic over the past couple of centuries (since the industrial revolution) then they have been in millions of years. Ph has dropped by .1 units already. This translates into an approximate 30% increase in hydrogen ions. This is dire news for the calcifying organisms of the ocean and because they make up a large percentage of the base of the food-chain, the rise in ph could be catastrophic for the entire ocean ecosystem.
Ph of the oceans has risen as a result of human activity. This is not debated, like climate change, this is a generally accepted fact. The burning of fossil fuels releases CO2 into the atmosphere which is 'absorbed' by the ocean where it forms carbonic acid which then dissociates to form hydrogen ions. Intensive study done in the ninteen-nineties indicates that the oceans have absorbed half of the anthropogenic CO2 emited since the beginning of the nineteenth century! This rise in acidity will primarily affect small calcifying organisms, which in turn could affect the rest of the ocean ecosystem.
"The Darkening Sea" is an excellent article on the relationship between calcifiers and ocean acidity it was published in the New Yorker in November of 2006. The article mentions a woman who studies Pteropods, a type of shell forming zooplankton. At one point while collecting samples she had to put several pteropods into the same container, the next day the shells of the pteropods had begun to dissolve. The CO2 that resulted from the metabolism of the pteropods had not been allowed to escape from the container, as a result it mixed with the surrounding water and increased the acidity in the sample jar. This was before concern had developed over ocean acidity and the dissolving shells were ignored. On a much larger scale fossil evidence reveals what happens when the entire atmosphere experiences a sudden increase in CO2 concentration.
At the end of the Paleocene epoch a great deal of CO2 showed up in the atmosphere over a matter of thousands of years. This is a relatively short amount of time in Earth history. According to fossil evidence many species (including many calcifying species and those above them on the food chain) went extinct at this time and new ones rose to dominance. The rate at which CO2 levels are increasing in the atmosphere now is on the scale of tens to hundreds of times more rapid than during the Paleocene. What will this mean for the future of ocean life?
Carol Turly, a scientist who worked on the Royal Society's report on ocean acidification believes there may be "a shortening of the food chain;" in other words a loss of Biodiversity with only one or two species at the top. Thomas Lovejoy, a prominant biologist who first used the term "biological diversity," suggests that the oceans will undergo a "de-evolution process" whereby invertebrates such as jelly fish could rise to dominance.
There will almost certainly be a catastrophic loss of biodiversity. For instanc, coral reefs are home to an estimated 25% of fish species. Coral reefs are made up of millions of polyps which build the non-living skeleton we know as coral by combining calcium and carbonate ions found in sea water. For the past few million years they have done this in an ocean with an aragonite concentration level between 4 and 5*. This level has now dropped to below 4 in all but a few regions of the world and is predicted to drop to 3 by 2100. Within our children's lifetime, it may become impossible for coral reefs to form at all.
Ocean acidification is a very serious and complex issue which has the scientific community in a general state of concern, if not panic. The consequences will be great and are already beginning to occur. The only hope of preserving some of our ocean's biodiversity is if we stop the burning of fossil fuels and find alternate sources of energy. I think it's worth hoping for.


*the concentration value is a result of a complex formula involving a ratio of the product of calcium and carbonate ions to something called the "stoichiometric solubility product."

References:
The Darkening Sea, By Elizabeth Kolbert, article appearing in the November 2006 issue of the New Yorker.
The Royal Society's report on Ocean acidity
available at http://royalsociety.org/document.asp?id=3249

1 comments:

Dominic B. said...

I never heard of de-evolution before...I will look into it...very interesting!