Monday, October 15, 2012

The Antarctic Paradox

A phytoplankton bloom off the
coast of Argentina.

Recently I wrote about how the population of Antarctic krill has dropped by 80% over the last 40 years. I have to admit, I was feeling a bit depressed after writing that column. It seems that the natural world is forever being drop-kicked at the expense of progress. But are the two competing worlds forever destined to be in conflict? Maybe not.
   Let’s look a little closer at the problem of declining krill numbers. It’s paradoxical that there are vast areas of the Southern Ocean that contain plenty of nutrients to support phytoplankton growth, the primary food source for krill, yet we don’t see the growth that would normally be expected. These low-plankton regions near Antarctica are called HNLC areas because the have High Nutrient yet Low Chlorophyll.
   The main reason for this is a lack if iron in the water. Iron is an element that is required in trace amounts for photosynthesis to take place, but it is insoluble in sea water, making it a limiting nutrient for plankton growth.
   Over the last 20 years, there has been considerable research into the problem and it has been shown that phytoplankton growth can be stimulated by adding iron. Usually such iron fertilization occurs naturally by ocean current upwellings, wind-born dust being deposited over the ocean’s surface or iron-rich minerals being carried to the ocean by glaciers or icebergs. 
   And there is another potential benefit beyond boosting the bottom of the food chain. When Mount Pinatubo erupted in 1991, it deposited about 40,000 tons of iron-rich dust into the world’s oceans. What happened as a result was remarkable: over the next few years, phytoplankton blooms increased substantially, causing planetary carbon dioxide levels to drop and oxygen levels to increase. It was estimated that over a billion tons of CO2 was removed from the atmosphere.
   There are now plans underway to do this on a large-scale, commercial basis. However, there is considerable uncertainty and disagreement as to whether it will do more harm than good on a large scale. Some scientists remain skeptical about whether the process would remove carbon dioxide for the long term and what the ecological impact will be. Further experimentation is needed and one thing is for certain: future policies and carbon-offset markets will emerge, and possibly without a sound scientific basis. Iron fertilization should be considered along with any other geoengineering solution. And if it feeds a few more whales in the process, all the better.

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