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Study: Kilauea lava triggered massive algae bloom

In the midst of the destruction during last year’s lower East Rift Zone eruption of Kilauea volcano, scientists from the University of Hawaii and the University of Southern California observed how one of nature’s most devastating forces can also create and sustain life.

Their study, published in Thursday’s edition of the journal Science, documents how millions of cubic tons of lava flowing into the ocean in lower Puna caused a cocktail of nutrients to rise to the surface — resulting in a massive algae bloom that could be seen from space. NASA satellite photos of the eruption showed water around the lava’s entry was turning green, signaling huge amounts of chlorophyll, the green pigment in algae and other plants responsible for photosynthesis, a process that converts light into energy.

A rapid-response scientific team on the UH research vessel Ka‘imikai-O-Kanaloa conducted round-the-clock operations in the vicinity of the lava entry to test water chemistry and the biological response to lava pouring into the ocean between July 13-17, 2018. What they discovered was a phytoplankton bloom more than 100 miles long and 20 miles wide caused by higher-than-normal nitrate levels, silicic acid, iron and phosphate in the water.

Since lava itself doesn’t contain nitrate, the massive bloom couldn’t have been predicted.

“One of the things that’s novel about this study is that we know that the lava was … heating up in deeper waters that have nutrients,” said Nick Hawko, co-lead author of the study and a postdoctoral researcher at USC who will join the UH-Manoa Oceanography Department in January 2010. “And because (the nutrients) were heating up, they became really buoyant and floated back to the surface.

“And that sort of mechanism wasn’t on our radar at all.”

Sam Wilson, a UH-Manoa microbial biogeochemist and the study’s other co-lead author, said the phytoplankton bloom was “very intimately tied to lava entering the ocean.”

“When the lava started entering the ocean … we started seeing the presence of this high abundance of phytoplankton,” Wilson said. “When you see something like that, the two processes, the growth of the phytoplankton and the entry of the lava into the ocean are intimately related. Then, it’s just figuring out the extent of this relationship.

“That started when the lava went into the ocean, and … the bloom dissipated after the lava stopped entering the ocean at such a large scale.”

“What we think happened is that the phytoplankton, the algae in the ocean, is constantly growing but is also constantly being eaten by grazers, like grass is being eaten by cows and goats and stuff,” added Hawko. “This new accumulation of nutrient being pushed up was enough for the phytoplankton to accumulate. But after a couple of days, it’s probably going to be eaten up.”

The authors suggest it’s possible this mechanism has led to similar ocean fertilization events in the past associated with the formation of the Hawaiian Islands and other significant volcanic eruptions.

Asked about changes in fish or marine mammals in the area because of the algae bloom, Hawko replied, “I think it’s hard to say at this point.”

“Unfortunately, we were not able to sample fish and figure out what ones were supported by lava and what ones were supported by other activities on the coastline,” he explained. “I’m not sure we can say anything definitively, but generally, algae is sort of the base of the marine food chain, so all other life that we see in the ocean, whether it’s fish or whales or giant squids, are … dependent upon this base of the marine food chain.”

In the future, the team hopes to sample the newly-formed pond at the bottom of Halema‘uma‘u crater at Kilauea’s summit and further investigate lava-seawater interactions in the laboratory. Wilson said the current study can be examined “on many scales.”

“The Kilauea 2018 eruption was devastating, with many homes, properties and items destroyed,” he said. “Yet at the same time, the lava going into the ocean fueled microscopic life, created new land and, while it was destructive, was also creative, as well. When you drill down to what we learned from a scientific perspective, we learned about what type of phytoplankton responded under these conditions. That’s very useful for us to know. When you add nutrients or add fertilizer … are we able to predict what types of plants grow? We can do that for land better than we can for the ocean. So when nature throws us a situation like this, it’s really a test for how well we know the ecosystem.

“It’s a great example of land-sea interactions. When you have these sort of boundary environments such as a land-sea interaction, you have the opportunity to create situations that don’t occur in either land or the ocean but at these boundaries.”

Email John Burnett at hawaiitribune-herald.com
Source: Hawaii Tribune Herald

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