How A Volcanic Eruption In Hawaii Triggered A Massive Algae Bloom

The algae 'superbloom' caused by the eruption of Hawaii's Mount Kilauea in 2018.

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Last year’s eruption of Hawaii’s Mount Kilauea released over 4 billion cubic feet of lava onto the island and surrounding ocean. To put this in perspective, that’s enough lava to fill 45,400 Olympic-sized swimming pools - assuming the lava does not melt through the bottom of the pool, of course.

Just three days after the eruption began, massive blooms of phytoplankton, or tiny light-absorbing algae, were in full swing.

The reason Mount Kilauea’s hot lava triggered phytoplankton populations to boom was initially a mystery to scientists. Hawaii, like most tropical places, is surrounded by waters lacking in nutrients like phosphorus and nitrogen. Given this, most tropical algae blooms are triggered when phosphorous and nitrate, a form of nitrogen, are added to the nutrient-deprived water. But this bloom was different.

Lava entering Hawaii's Kapoho Bay during the eruption of Mount Kilauea in June of 2018.

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“There was no reason for us to expect that an algae bloom like this would happen,” said Dr. Seth John, geologist at USC Dornsife and co-author on a new study of the algae bloom. “Lava doesn’t contain any nitrate.”

During the eruption, the seawater surrounding Hawaii’s algae bloom was chocked full of nitrate - but where was it all coming from?

Now, new research published by John and collaborators in Science may explain why Mount Kilauea’s eruption is linked to this massive algae bloom.

Instead of adding nutrients to the water, scientists now suspect the shear heat of the lava caused the water near the seafloor to heat up, creating an underwater pressure-gradient known as ‘upwelling’. This upwelling may have then caused deep-sea nutrients, which are normally inaccessible to light-dependent algae at the ocean’s surface, to plume up and release a ‘pandora’s box’ of algae-fertilizing nitrate, fueling their rapid overgrowth.

“All along the coast of California, there is regular upwelling,” said John. “All the kelp beds and marine creatures that inhabit those ecosystems are basically driven by those currents that draw fertilizing nutrients up from deep water to the surface. That is essentially the same process that we saw in Hawaii, but faster.”

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