海洋铁施肥：气候救星还是生态赌博？
Iron, paradoxically, is the limiting nutrient in roughly a third of the world’s ocean, where its scarcity starves phytoplankton of the means to photosynthesize. The idea of deliberately sprinkling iron sulfate across these marine deserts — to trigger colossal algal blooms that might sequester atmospheric carbon — has hovered at the frayed edge of climate science for over three decades. It is a proposition that marries the audacity of geoengineering with the humility of a gardener: fertilize the sea, and hope the carbon sinks.
The hypothesis emerged from the late John Martin, the marine biogeochemist whose wry maxim — “Give me half a tanker of iron, and I’ll give you an ice age” — crystallized both its promise and its hubris. Early field trials, notably IronEx I and II in the equatorial Pacific and the Indo-German LOHAFEX experiment in the Southern Ocean, confirmed that iron addition indeed triggers rapid phytoplankton blooms, visible from space as green swirls. Yet the carbon that was supposed to sink into the abyss often stayed in the surface layer, recycled by zooplankton or decomposed back into CO₂, leaving the net drawdown disappointingly modest.
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