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The Big Island’s lava-spewing volcano has torched neighborhoods, choked vegetation and desiccated a lake. But in the open ocean, scientists are finding surprising new evidence that Kilauea’s apocalyptic ooze is breathing new life into the sea.
Phytoplankton blooming off the coast of Puna has grown so dense since the onset of the Lower East Rift Zone eruption that it can be seen from outer space. Discovered by satellite, this floating algae plume is born of the swift rivers of mineral-rich lava draining into the ocean since May.
For the first time, scientists are studying the little-understood microbiology of lava mixing into the sea. As they pioneer this research, they’re learning that when volcanic ash and molten rock rush into the ocean, they enrich the water with iron and phosphorus — essential nutrients that help plants grow.
“Lava is ultimately a fertilizer for the plants that live in the ocean,” said David Karl, a microbial oceanographer at the University of Hawaii Manoa. “Not only is it causing plants to grow that produce oxygen that helps us breathe, but these plants are also important because they absorb carbon dioxide and serve as the foundation of the marine food web.”
Although thousands of underwater volcanoes inject lava onto the seafloor, a periodic phenomenon that is little-studied, there are few land volcanoes that send lava into the sea.
Scientists have examined the aftermath of lava ocean entries in the near-shore waters of Iceland, the Aleutian Islands and the Mariana Islands. But this postmortem research has depended on scientific measurements derived from space.
During Kilauea’s Pu‘u ‘O‘o-Kupaianaha eruption in 1986, UH scientists sampled the seawater near the lava’s ocean entry zone to study the chemistry of the interaction. But the microbiology of Kilauea’s lava when it gushes into the open ocean and spreads miles out to sea has not previously been tackled by the scientific community.
“What you have for the very first time here is scientists looking at lava entry at the ocean’s surface,” said Sam Wilson, a UH assistant researcher and the chief scientist of the expedition. “It has predominantly been geologists and geophysicists that get excited about such a rare occurrence, but now oceanographers and ocean biologists are also taking note. There’s a lot that we don’t know.”
The phytoplankton plume off Cape Kumukahi is approximately 100 miles long and a mile wide — but it cannot be seen with the naked eye. That’s because phytoplankton, which feed the zooplankton on which small fish dine, are microscopic in size.
When scientists sampled the plume over four days in mid-July, the phytoplankton was producing plant pigment concentrations nearly 10 times higher than normal, according to Wilson.
Unable to see this phenomenon with their own eyes, the 19-member team of scientists at sea located the plume by measuring variations in the ocean’s chlorophyll content. The results are forthcoming.
The lava, however, did produce one visible change: Rather than royal blue, the expanse of deep water skirting the lava’s ocean entry point appeared light turquoise, like a shallow swimming pool, to the human eye.
The lighter pigmentation, Wilson hypothesized, could be the result of a reaction between the seawater and the minerals in the lava. The cause of this color shift is still under study.
Water samples collected during the expedition are now being analyzed in labs around the world.
Scientists on the cruise also deployed surface and underwater drones to gather data on ocean temperature, salinity, color and oxygen level. Some of these drones are still active.
A researcher who joined the cruise from Western Washington University stationed a series of ocean bottom seismometers near the shoreline to collect motion data.
In late July, the U.S. National Science Foundation awarded Karl and another professor more than $180,000 in grant money to advance their work.
The July expedition cost about $200,000, with the 200-foot research vessel averaging $45,000 per day.
Karl said he hopes to send a research team back to Big Island waters for another round of data collection in October.
Algae plumes such as this one are rare, but not unheard of, in Hawaiian waters, according to Karl. Often they are the product of springtime dust storms that blow across the Pacific Ocean from the deserts of China.
“We see these plumes off Hawaii a couple times a year and we have always been perplexed,” Karl said. “How are they generated? How are they sustained? We don’t know that, and yet the turtles are following these plumes and the fish and the birds are following these plumes. This shows us how little we know about life in the sea.”
In the last week, the 3-month-old algae plume has been shrinking as the volcano enters a quiet phase and the lava pouring into the ocean subsides. When phytoplankton can’t access the nutrients it needs to grow, it can die in the course of a day.
It’s unclear how long the plume will persist without a stronger flow of lava.
“The volcano has ceased its major eruption at the summit and the ocean entry has almost stopped entirely, and sure enough the plankton bloom is dissipating,” Karl said. “We would like to be out there to see the demise.”
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