Research finds Tonga eruption spawned massive phytoplankton bloom: Big Island Now

Ocean chlorophyll maps from before (left) and after (right) the January Hunga Tonga-Hunga Ha’apai eruption in the Kingdom of Tonga. (Barone, et al., 2022)

Flowery, baby, flowery.

A new study by a team of scientists from the University of Hawai’i at Mānoa and Oregon State University revealed that the largest underwater volcanic eruption of the century led to a spectacular bloom of microscopic marine life that covered an area nearly 40 times the size of Oʻahu.

The burst of phytoplankton growth north of the island of Tongatapu in the Kingdom of Tonga occurred within 48 hours of the Hunga Tonga-Hunga Haʻapai eruption. Phytoplankton are tiny photosynthetic organisms that produce oxygen and serve as the basis of the marine food web. The growth of these microbes can increase rapidly when nutrients become available.

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“Even though the Hunga Tonga-Hunga Ha’apai eruption was underwater, a large ash plume reached a height of tens of kilometers into the atmosphere,” Benedetto Barone, lead study author and research oceanographer to Center for Microbial Oceanography: research and teaching at UH-Mānoa School of Ocean and Earth Science and Technology, said in a press release. “The ashfall provided nutrients that stimulated the growth of phytoplankton, which reached concentrations well beyond typical values ​​seen in the region.

Hunga Tonga-Hunga Haʻapai eruption seen from the GOES satellite. Credit: NASA/NOAA

Three of the study authors previously assessed and sampled a smaller phytoplankton bloom linked to the 2018 Kīlauea eruption on the Big Island.

“It was quite simple to modify the computer code I had written to analyze satellite measurements around Hawaii to determine the impact of the Tonga eruption on the nearby ocean ecosystem,” Barone said in the statement. Press. “From the first moment we saw the results of the analysis, it was clear that there had been a rapid phytoplankton response in a large area.”

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The research team was led by the School of Ocean and Earth Science and Technology. He analyzed satellite images, radiation emission and light reflection from the sea surface and determined that the deposition of volcanic ash after the Hunga Tonga-Hunga Ha’apai eruption was probably the most important source. important amount of nutrients responsible for the massive growth of phytoplankton.

“We were impressed to observe the vast region with elevated chlorophyll concentrations in such a short time after the eruption,” said Dave Karl, study co-author and director of the Center for Microbial Oceanography: Research and Education. “It shows how quickly the ecosystem can respond to nutrient fertilization.”

The eruption was a natural fertilization event that revealed the ability of phytoplankton to react quickly – when the right conditions present themselves.

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“A casual observer could see seemingly very different parts of the environment – in this case, a volcano producing a large eruption and a major shift in the ecology of nearby oceans,” said Ken Rubin, co-author of the report. ‘study and volcanologist at the School of Ocean and Land Sciences and Technologies Department of Earth Sciences. said in the press release. “However, our observations illustrate the broad interconnection and interdependence of different aspects of the environment, perhaps even indicating an underappreciated link between volcanism and shallow marine ecosystems on a global scale.”

Phytoplankton extract carbon dioxide, responsible for global warming, from the atmosphere. Barone said the dynamics of the huge phytoplankton bloom after the Tonga eruption can help predict the behavior of pelagic environments, when nutrients are added to nutrient-poor regions of the ocean.

“This knowledge may prove useful in the discussion of the impacts of carbon dioxide removal technologies based on ocean fertilization,” Barone said.

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