What Would Be the Side Effects of Iron Fertilization?

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Image courtesy of NASA

Amidst all the hullabaloo over the supposed upsides and downsides of iron fertilization, it's been hard to find a single story explaining what potential ramifications its use could incur. This latest article - part of a longer series investigating the consequences of manipulating ecosystems - provides one of the best overviews on this tricky subject. As Andrew Watson, an oceanographer from the University of East Anglia, made clear at a conference on iron fertilization held at WHOI last September, "there's quite a range of things that are going to happen when you do that," suggesting that drawing down atmospheric carbon dioxide and sequestering it in the deep sea - the desired effects - could be only two of many possible consequences. The potential ways through which iron fertilization could harm the ocean - a lengthy list compiled by the Scientific Group of the London Convention - include the side effects from the added iron; the effects from plankton growing and dying; the indirect effects of nutrients cycling through the oceans; and the physical effects of having more plankton in the same amount of space.

For one thing, scientists are worried by the changes in species composition the added iron could effect; past studies have demonstrated that the addition of iron sparked higher levels of interspecific competition, inevitably benefiting some species over the others. While there is the chance that more frequent phytoplankton blooms could provide a larger, constant food supply - particularly for dwindling fish stocks - scientists point out that iron addition could just as easily support less beneficial processes in the oceans, increasing harmful algal blooms and dead zones.

There is also the concern that the changes in water chemistry caused by iron fertilization could lead to higher emissions of both nitrous oxide, two highly potent GHGs produced when organic matter decomposes in deep waters. Some have tried to downplay these concerns by proposing alternate solutions - fertilizing low-nutrient regions instead of high-nutrient ones to offset nutrient depletion, for example - or by arguing that not all side-effects need be undesired. Because many phytoplankton release dimethylsulfide (DMS) into the atmosphere, they believe bigger blooms could create a larger aerosol effect, helping to block incoming sunlight and cooling the planet.

It is a complicated situation, to be sure, but one that - as many have have long argued - can and needs to be resolved within the scientific community before drastic action is taken.

Via ::Oceanus: What Are the Possible Side Effects?