Tonga volcano eruption caused a massive phytoplankton bloom after just 48 hours

Using satellite images of various kinds, such as true color, emission of red and infrared radiation, and light reflection at the sea surface, researchers saw a 10-fold increase in phytoplankton near the volcano.

How a volcanic eruption stimulated life?

Phytoplanktons are microscopic photosynthetic organisms that live suspended in water. Like land plants, they take up carbon dioxide, make carbohydrates using light energy, and release oxygen. They are what are known as primary producers of the ocean—the organisms that form the base of the food chain.

The growth of these microorganisms is often limited by the low concentrations of nutrients dissolved in the surface ocean, but phytoplankton can increase rapidly when nutrients become available.

According to the study, the Tonga eruption could have supplied nutrients to these microbes from both above, through atmospheric ash deposition, and from below, through the upwelling of seawater containing a volcanogenic component (hydrothermal fluids, water that came into contact with hot magmatic products, or condensed volcanic vapors emitted into seawater).

"Even though the Hunga Tonga-Hunga Haʻapai eruption was submarine, a large plume of ash reached a height of tens of kilometers into the atmosphere," said Benedetto Barone, lead author of the study and research oceanographer at the Center for Microbial Oceanography: Research and Education (C-MORE) in SOEST. "The ash fallout supplied nutrients that stimulated the growth of phytoplankton, which reached concentrations well beyond the typical values observed in the region."

Such a volcanic eruption has led to similar ocean fertilization events in the past, including the smaller phytoplankton bloom after the Kilauea eruption of 2018, highlighting the potential impacts of volcanic eruptions on ocean ecosystems.

Understanding ocean fertilization

Phytoplankton uses atmospheric carbon dioxide and generates about half of the oxygen in Earth's atmosphere. Even small changes in the growth of phytoplankton may affect atmospheric carbon dioxide concentrations, which would feed back to global surface temperatures.

The Hunga Tonga-Hunga Haʻapai volcano eruption was a natural fertilization event that revealed the capacity of these microscopic powerhouses to respond fast when the right conditions arise.

"The dynamics of this event can help us predict the behavior of pelagic environments, when nutrients are added to nutrient-impoverished regions of the ocean," said Barone. "This knowledge can prove useful in the discussion about the impacts of carbon dioxide removal technologies based on ocean fertilization."