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Volcanic ash as a nutrient source: the impact of the Hunga Tonga eruption on the South Pacific ecosystem

GEOTRACES GP21 cruise track and Hunga Tonga Hunga Ha’apai (HTHH) volcanic eruption scattering volcanic ash. Credit: Nature Communications (2024). DOI: 10.1038/s41467-024-52904-3

The January 2022 eruption of Hunga Tonga Hunga Ha’apai (HTHH) released approximately 2.9 billion tons of volcanic material into the atmosphere and across the South Pacific. In early 2022, a scientific expedition (GEOTRACES GP21) investigated the impact of this monumental event on the biogeochemistry of South Pacific Gyre (SPG) surface waters.

The scientists specifically focused on changes in trace element concentrations in the ocean and their effects on marine life. The findings are now published in the journal Nature Communications.

By computer and ship: Evidence of volcanic influence in the South Pacific

To comprehensively analyze the effects of the eruption, researchers used a combination of advanced computer simulations and precise sample analysis. To simulate the spread of volcanic ash after an eruption, they used the HYSPLIT computer model from the US federal agency National Oceanic and Atmospheric Administration (NOAA).

This model simulates the transport of substances in the atmosphere. This was used to calculate the dispersion of volcanic ash at different altitudes over a 72-hour period and the trajectory of the volcanic ash over a period of up to 315 hours.

During the SONNE expedition SO289 as part of the international GEOTRACES program, which took place from February to April 2022, researchers collected water samples along a designated route to determine the distribution of trace elements and their biogeochemical properties. The impact was analyzed. During the expedition, large quantities of floating tephra, mainly pumice, were observed and collected by Western SPGs.

Using radioactive neodymium isotopes and rare earth element concentrations, researchers were able to identify evidence of significant volcanic input into the western SPG region. This area has been identified as a major site of post-eruption deposition based on volcanic ash scattering models. Additionally, we used seawater analysis of neodymium isotopes and rare earth elements to track volcanic input and chlorophyll a as an indicator of phytoplankton.

Phytoplankton benefit from trace elements in volcanic material

In the Western SPG, researchers identified large amounts of trace elements such as iron and neodymium, which typically enter the ocean in very small amounts through atmospheric dust. The volcanic eruption released an additional 32,000 tons of iron and 160 tons of neodymium. The amount of iron is equivalent to what the region normally receives in one year, and the amount of neodymium is equivalent to one year’s worth of global input.

“At the same time, we measured an increase in the concentration of chlorophyll-a in surface water, which indicates an increase in phytoplankton proliferation and therefore biological activity,” said Dr. said author Dr. Zhouling Zhang.

Long-term climate impacts

The research team was able to show that trace elements released by volcanic eruptions play an important role for marine life. These elements, especially the micronutrient iron, act as nutrients that stimulate phytoplankton growth in the ocean.

Phytoplankton play an important role in the global carbon cycle by absorbing COâ‚‚ from the atmosphere through photosynthesis and storing it in the ocean. Improving biological productivity could therefore also improve the ocean’s ability to absorb COâ‚‚ from the atmosphere, and this process could have long-term effects on the climate.

The researchers estimate that the micronutrient iron release from the HTHH eruption is comparable to the iron fertilization caused by the June 1991 eruption of Mount Pinatubo in the Philippines. Approximately 40,000 tons of volcanic material was released during this time, slowing volcanic activity by 1.5 ppm. The rise in atmospheric COâ‚‚ was measured approximately two years after the eruption.

“We think that a Hunga Tonga eruption could have a similar effect,” Chan said.

Further information: Zhouling Zhang et al., 2022 Hunga Tonga-Hunga Ha’apai eruption injects large amounts of trace metals into the South Pacific, Nature Communications (2024). DOI: 10.1038/s41467-024-52904-3

Provided by Helmholtz German Research Center Association

Citation: Volcanic ash as a nutrient source: How the Hunga Tonga eruption affected the South Pacific ecosystem (November 6, 2024) https://phys.org/news/2024-11-volcanic-ash- Retrieved November 6, 2024 from source-nutrients-hunga.html

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