Bloomin’ Quakes

It’s hard to think of anything good coming from earthquakes. But for life in part of the Southern Ocean, they could be crucial. A recent study found that underwater quakes could intensify “blooms” of phytoplankton.

These tiny plant-like organisms form the base of the marine food web. They also absorb carbon dioxide from the air, and release oxygen. So anything that bumps up their numbers a bit is good for life in the Southern Ocean and around the planet.

Every spring and summer, a big bloom develops between Antarctica and New Zealand and Australia. But three decades of satellite photos revealed a huge range in the size of the bloom. Some years, it covers an area the size of Delaware. In others, it can be dozens of times larger—as big as California.

The blooms are fed by iron—a key nutrient. But there’s not a lot of it in the Southern Ocean. And the location of the annual bloom isn’t near any of the most common sources of iron. So researchers looked for a “deeper” cause.

They found that the bloom occurs in a region with lots of underwater volcanoes. “Vents” pump hot, iron-rich fluids into the water—possibly feeding the bloom.

Records of volcanic activity in the region showed that, when the ocean floor was rocked by earthquakes of magnitude five or greater in the months before a bloom, the event was much bigger. The tremors might clear out blocked vents, or create new ones, boosting the amount of iron in the water—a positive impact for earthquakes.

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