Thwarted By Planktivores

I’ve never been a fan of the proposed iron fertilization experiments used in open ocean systems to encourage phytoplankton growth in an attempt to sequester carbon. Why not? The ocean is a big complex place. That sort of logic might make you think that a little bit of iron supplementation here and there couldn’t hurt. Certainly, there have been arguments that we’re just synthetically simulating the natural dust (and subsequent iron) fallout into the eastern Atlantic from Saharan sand, for instance. However, the complexity of the ocean and its vastness means that the connected webs that drive ocean systems are incredibly variable, volatile, and that outcomes are undeniably hard to predict.

One of the most recent iron experiments received coverage in New Scientist last week (I love that the magazine posts appear online as well). The Lohafex experiment in the Southern Ocean was thwarted when phytoplankton other than diatoms bloomed and failed to fall out to the ocean floor and sequester carbon. Instead the bloom did what most blooms do near the Antarctic; it attracted swarms of copepods, krill, and subsequent predators and fed into the larger foodweb.

While that certainly cleans up the iron-addled plankton, it doesnt precisely sequester carbon into the deep ocean sink that researchers predicted. The carbon is now “sunk” into the bodymass of the predators in the system and the waste produced by the animals as they were consuming through the trophic levels all the way up. Of course the waste might fall out itself as marine snow. So I suppose that could be helpful towards the intended goal of the iron fertilization protocol.

It all makes you wonder how we came to believe that purposefully altering incompletely understood systems would be a good idea. We dont know enough about ocean systems to attempt to bridle them into serving our needs and goals on such a highly variable scale as carbon sequestration. Even if there had been enough diatom growth and more of the plankton had reached the ocean floor who’s to say it would remain there for very long? Is it really possible to predict, with any accuracy, the lifecycle of a carbon atom as it moves from the atmosphere, into the ocean, into the plankton bloom, into the biomass, down as marine snow, and towards the ocean floor? Would it even make it that far before a snow-consumer came along and gobbled it up?

Maybe I’m working too hard off that precautionary principle. Is it just me, or doesn’t it seem unwise to tinker with a system just to see what happens when we poke it?

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