The
suggestion to use the
ocean to soak up the excess carbon dioxide in the
atmosphere (see point
2. Biology: Seeding above in
The Alchemist's writeup) stems from a
discovery made by John H. Martin. There are zones of significant size which have been called
HNLC areas (for
High
Nutrient Low Chlorophyll), in which there is sufficient
phosphorus,
nitrogen and
silica to permit good
algal growth, but little such growth occurs. Martin determined that, while there was an abundance of the normally limiting nutrients in these zones, there was a significant lack of
iron in the water. While it is not normally limiting to plants, a certain amount of iron is require for cell construction and
cell division.
Martin suggested that this hypothesis could be verified on a large scale by seeding parts of the ocean with iron, and observing the reaction of the algal community. Despite a firestorm of controversy over the proposed experiment, funding was acquired. In October, 1993, the research vessel Columbus Iselin left Miami and headed towards the Galapagos Islands in the Pacific, one of the well known HNLC zones. This expedition took place without Martin, as he had passed away from prostate cancer earlier that year.
The team deployed, in a single day, nearly a thousand pounds of iron, and began to note the progress. Very quickly (overnight, in fact), a response was observed. One scientist has since stated that he was able to smell the algae growing. For the next nine days the crew followed the algal bloom, and determined that overall productivity was increased three-fold by a relatively minor ion addition.
After this experiment was published and similar work was conducted in other areas to verify the global nature of the phenomenon, it was suggested that these regions be used to soak up some of the excess C02 that has been building in the atmosphere for a century. Now, it must be stressed that Martin stated, prior to his death, that he would never advocate large scale iron fertilization of the ocean until the consequences and mechanisms were fully understood. Nonetheless, it became such a popular idea amongst a certain circle (*cough* the oil industry *cough*) and their attendant engineering colleagues that three (there may be more now) patents on ocean fertilization technologies were requested (and granted, in the infinite wisdom of the U.S. Patent Office).
There is significant scientific concern over the proposal to fertilize the ocean in order to reduce the CO2 load in the atmosphere. Let alone the escaping of responsiblity and the forgoing of the concept of sustainable development that is inherent in the very idea, there are serious worries about what such a fertilization might do. First, we know it will change the composition (taxonomic) of the algal community in the region affected, which will have impacts on the invertebrates and vertebrates in the food web (this will, undoubtably, affect the fishing industry). Second, it is at best a temporary solution, as fertilization's effects are relatively short lived (on the scale of days to weeks). Finally, and perhaps most worrisome, is the fact that all of that carbon, trapped in algal cells, has to go somewhere. The original experiments showed that the grazers in the ocean were not able to consume all of the algae produced by fertilization, and that this algae died and sank. Upon sinking through the thermocline, the algal cells (with the now absorbed carbon) passed from an oxic to anoxic zone, and began to decay on the ocean floor. When algae decays in an anoxic environment, two products result: hydrogen sulfate (H2S) and methane (CH4). These two gasses are far more effective at trapping solar energy in our atmosphere, and thus iron fertilization may well result in a worsening of the global warming problem.
This is not to say that there aren't still certain people pushing for this solution. At times, it seems, the appearance of positive behaviour is more important that the consequences of our actions ...