By Lina carolina 
The catastrophic eruption of Kīlauea Volcano on Hawaiʻi Island in May 2018, a geological event of immense power, unleashed an extraordinary consequence far from its fiery source: a colossal summertime phytoplankton bloom across the North Pacific Subtropical Gyre. For the first time, a landmark study published in JGR Oceans by an international consortium of researchers has definitively linked the volcanic ash, propelled skyward in a plume reaching nearly five miles high, to this rare and massive oceanic bloom. The ash, transported by prevailing winds for approximately 1,200 miles west of the volcano, acted as a vital nutrient source, triggering an explosion of microscopic marine life in an area typically characterized by nutrient-poor waters.
A Volcanic Fury Unleashes Oceanic Life
The 2018 Kīlauea eruption was not merely an isolated geological incident; it was one of the most significant volcanic events to occur in Hawaiʻi in over two centuries. The eruption commenced on May 3rd, 2018, with the dramatic fountaining of lava from the summit caldera and the subsequent fissures that opened in the Lower East Rift Zone. Over the ensuing months, millions of cubic feet of molten rock cascaded into the Pacific Ocean, creating new landmasses and altering the coastline of Hawaiʻi Island. Beyond the visible spectacle of lava flows and incandescent ash plumes, the eruption released staggering quantities of gases into the atmosphere. Estimates suggest that Kīlauea was spewing approximately 50 kilotons of sulfur dioxide and around 77 kilotons of carbon dioxide daily into the atmosphere during its most active phases.
However, it was the fine particulate matter – the volcanic ash – that traveled the farthest and had the most unexpected impact. This ash, laden with essential minerals, embarked on an atmospheric journey, carried by powerful jet streams and prevailing winds. While volcanic ash has been known to influence local ocean conditions near Hawaiʻi Island, its capacity to fertilize vast expanses of the open ocean thousands of miles away had remained largely theoretical. The 2018 Kīlauea eruption provided a dramatic, large-scale case study.
Unraveling the Link: Ash to Bloom
The research team, a collaboration of scientists from the University of Hawaiʻi at Mānoa, Universiti Malaya, and the National Taiwan Ocean University, meticulously pieced together the causal chain. Their investigation began with analyzing satellite imagery that tracks atmospheric aerosols, essentially measuring the “haze” or optical clarity of the sky. These observations confirmed the widespread dispersal of ash particles westward from Kīlauea.
"The trajectories of the ash were recorded by Earth-orbiting satellites that detect changes in the optical clarity of the atmosphere, the so-called aerosol optical depth," explained Wee Cheah, the study’s corresponding author and a Senior Lecturer at the Institute of Ocean and Earth Sciences at Universiti Malaya. "Depending on the density, size, and shape of the particulate matter and local atmospheric conditions, especially rainfall, the ash eventually falls out of the atmosphere and into the surface ocean."
Following the ash’s aerial journey, the scientists then turned their attention to the ocean’s surface. Satellite sensors that detect ocean color, a proxy for the presence and abundance of phytoplankton, revealed a startling phenomenon. In the summer of 2018, a vast and unusually persistent bloom of phytoplankton emerged in the North Pacific Subtropical Gyre, a region typically characterized by oligotrophic conditions – meaning it has very low concentrations of essential nutrients.
A Bloom of Unprecedented Scale
David Karl, a study co-author and the Director of the Center for Microbial Oceanography: Research and Education at the University of Hawaiʻi (UH) at Mānoa School of Ocean and Earth Science and Technology, described the bloom’s magnitude with awe. "The scale and duration of this bloom were both massive, and probably the largest ever reported for the North Pacific," he stated. "Our study shows the connection between the eruption of Kīlauea and bloom formation far from the volcano."
Phytoplankton, microscopic marine algae, form the base of the oceanic food web. Their growth is primarily limited by the availability of nutrients, such as nitrogen, phosphorus, and iron. The North Pacific Subtropical Gyre is known for its nutrient-depleted surface waters, a consequence of its location far from major terrestrial nutrient inputs and its stratified oceanographic structure, which prevents deep, nutrient-rich waters from reaching the sunlit surface.
The volcanic ash, however, introduced a critical influx of these limiting nutrients. "The waters in the open ocean of the Pacific are nutrient depleted and the addition of volcanic ash, especially iron in the ash, and to a lesser extent other trace elements and possibly phosphate, can stimulate the growth of marine phytoplankton, especially the so-called nitrogen-fixing microbes that can grow in the absence of additional nitrogen," Karl elaborated. Iron, in particular, is a key micronutrient that often limits phytoplankton growth in such oceanic regions. The ash provided a readily available source of this essential element, effectively fertilizing the vast expanse of the gyre.
Chronology of a Volcanic Fertilization Event
The chain of events, reconstructed by the research team, paints a clear chronological picture:
- May 3, 2018: Kīlauea Volcano erupts, launching an immense plume of ash and gases high into the atmosphere.
- May – July 2018: Prevailing winds transport volcanic ash particles westward across the Pacific Ocean. Satellite observations of aerosol optical depth confirm the widespread dispersal.
- June – August 2018: The ash particles, gradually settling out of the atmosphere, deposit onto the surface of the North Pacific Subtropical Gyre, approximately 1,200 miles west of Hawaiʻi.
- July – September 2018: The deposited ash, rich in essential nutrients like iron, fertilizes the nutrient-poor surface waters. This triggers a massive and prolonged bloom of phytoplankton.
- July – October 2018: Satellite ocean color data detects the extensive phytoplankton bloom, a feature unprecedented in its scale and duration for this region. The bloom is also corroborated by data from autonomous Argo floats deployed in the area.
- Publication: The findings are published in the peer-reviewed journal JGR Oceans, formally establishing the link between the Kīlauea eruption and the oceanic bloom.
Broader Implications for Oceanography and Climate Science
The implications of this research extend far beyond understanding a single volcanic event. It provides crucial insights into the complex interplay between terrestrial geological processes and marine ecosystems, with significant consequences for the global carbon cycle.
Carbon Sequestration: A Natural Carbon Sink
One of the most compelling findings of the study is the role of the phytoplankton bloom in sequestering atmospheric carbon dioxide. As the phytoplankton flourish, they absorb carbon dioxide from the atmosphere through photosynthesis. When these microscopic organisms eventually die, their organic matter sinks to the deep ocean, effectively removing carbon from the upper ocean and atmosphere for extended periods.
"The growth of these specialized phytoplankton produced a lot of organic matter. When the organisms die and sink to the deep ocean, a large amount of organic carbon is exported from the surface, essentially removing carbon from the upper ocean and atmosphere," the study explains.
The researchers have estimated the magnitude of this carbon sequestration. "Our estimates are that export of organic carbon may be equivalent to about half of the carbon dioxide initially released from the eruption," stated Karl. This suggests that natural events, such as large volcanic eruptions, can act as significant, albeit temporary, carbon sinks, partially offsetting the greenhouse gas emissions.
This discovery has profound implications for our understanding of the ocean’s role in regulating Earth’s climate. It highlights that the ocean is not a passive recipient of atmospheric carbon but an active participant in carbon cycling, influenced by both natural and anthropogenic factors.
Refining Phytoplankton Bloom Dynamics
The study also promises to refine our understanding of phytoplankton bloom dynamics, particularly in the context of nutrient limitation in the open ocean. Previously, the North Pacific Subtropical Gyre was not considered a prime candidate for such massive blooms. This research demonstrates that external nutrient inputs, even from distant volcanic events, can override typical oceanic conditions and trigger significant biological responses.
"This can be used to refine our understanding of phytoplankton bloom dynamics and to improve our understanding of the ocean’s carbon cycle," Karl emphasized. This improved understanding is critical for developing more accurate climate models and predicting the future behavior of marine ecosystems in a changing world.
Future Monitoring and Research
The research team is now poised to leverage this groundbreaking discovery for future monitoring and research. They are prepared to track future volcanic eruptions and their potential impacts on phytoplankton blooms. The success of this study, which relied heavily on satellite remote sensing and data from autonomous floats, underscores the power of these technologies for oceanographic research.
"If another major eruption occurs, they plan to deploy a research vessel to study the bloom’s development and response in real-time," the article states. Such dedicated fieldwork would provide invaluable ground-truth data, allowing scientists to observe the bloom’s progression firsthand, collect samples, and further elucidate the intricate biological and chemical processes at play. This proactive approach could lead to even more precise measurements and a deeper comprehension of the complex relationships between volcanism, oceanography, and climate.
The 2018 Kīlauea eruption, a powerful reminder of Earth’s dynamic geological forces, has unexpectedly illuminated a crucial connection between the planet’s fiery interior and the vast, life-sustaining oceans, offering new perspectives on our planet’s intricate systems.
