By Lina carolina 
The colossal eruption of Hawaiʻi’s Kīlauea volcano in May 2018, a spectacle that unleashed an estimated 1.3 billion cubic meters of lava and sent an ash plume nearly five miles into the stratosphere, has been definitively linked to a rare and extraordinarily large summertime phytoplankton bloom in the North Pacific Subtropical Gyre. This unprecedented event, occurring approximately 1,200 miles west of the volcano, was triggered by the deposition of volcanic ash particles onto the ocean’s surface, according to a groundbreaking new study published in the esteemed scientific journal JGR Oceans. The international research team’s findings illuminate a previously underappreciated connection between terrestrial volcanic activity and oceanic productivity, with significant implications for our understanding of marine ecosystems and the global carbon cycle.
A Cascade of Ash and Life in the Open Ocean
The North Pacific Subtropical Gyre, a vast expanse of the ocean characterized by its oligotrophic (nutrient-poor) conditions, is not typically known for supporting massive biological events. However, the summer of 2018 witnessed an anomaly of immense proportions. The study reveals that the fine particulate matter ejected by Kīlauea, carried by prevailing atmospheric currents, settled upon this remote oceanic region, acting as a potent fertilizer for the microscopic marine algae known as phytoplankton.
"The scale and duration of this bloom were both massive, and probably the largest ever reported for the North Pacific," stated David Karl, a co-author of the study and Director of the Center for Microbial Oceanography: Research and Education at the University of Hawaiʻi at Mānoa’s School of Ocean and Earth Science and Technology. "Our study shows the connection between the eruption of Kīlauea and bloom formation far from the volcano. This can be used to refine our understanding of phytoplankton bloom dynamics and to improve our understanding of the ocean’s carbon cycle."
The Unfolding of an Unprecedented Event: A Chronology
The Kīlauea eruption commenced with a series of explosive events in May 2018, following months of increased seismic activity and summit collapses. The initial phase of the eruption was particularly vigorous, characterized by lava fountaining and the rapid effusion of lava flows that ultimately consumed large areas of the Puna district on Hawaiʻi Island. During this period, the volcano released an estimated 50 kilotons of sulfur dioxide and about 77 kilotons of carbon dioxide into the atmosphere daily, alongside vast quantities of volcanic ash.
While Kīlauea is one of the world’s most active volcanoes, with numerous eruptions in the past four decades, the direct link between its ashfall and widespread open-ocean phytoplankton blooms had not been previously established. The 2018 eruption, however, was of exceptional magnitude, described as one of the largest in over 200 years. This scale of explosive activity was crucial for propelling ash particles to high altitudes, enabling their long-range atmospheric transport.
May 2018: Kīlauea volcano erupts explosively, injecting significant amounts of ash and gases into the atmosphere.
Weeks and Months Following: Prevailing winds transport ash particles westward across the Pacific Ocean. Satellite imagery begins to detect changes in atmospheric optical clarity due to the presence of these aerosols.
Summer 2018: Volcanic ash settles onto the surface of the North Pacific Subtropical Gyre, approximately 1,200 miles west of Hawaiʻi.
Throughout Summer 2018: The deposited ash, rich in essential nutrients like iron, stimulates unprecedented phytoplankton growth, creating a massive bloom detectable by satellite sensors.
Post-Bloom Period: As the phytoplankton die, a significant portion of their organic matter sinks to the deep ocean, sequestering carbon.
Present Day: A new study published in JGR Oceans confirms the causal link between the Kīlauea eruption and the North Pacific bloom, providing critical insights into oceanographic processes.
Unraveling the Mechanism: From Ashfall to Algal Bloom
The research meticulously details the pathway from volcanic eruption to oceanic bloom. Wee Cheah, the study’s corresponding author and Senior Lecturer at the Institute of Ocean and Earth Sciences at Universiti Malaya, explained the atmospheric transport mechanism. "After the 2018 eruption, the prevailing winds transported ash particles to the west," Cheah stated. "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. 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."
The study leveraged advanced satellite remote sensing techniques. Chun Hoe Chow, the lead author and Associate Professor in the Department of Marine Environmental Informatics at the National Taiwan Ocean University, along with his co-authors, analyzed satellite data that measures ocean color. This indirect indicator of phytoplankton abundance revealed a massive bloom situated near the dateline. Their comprehensive analysis also investigated the physical conditions of the ocean, aiming to explain both the unusual timing and location of this significant surface bloom, which is atypical for this nutrient-starved region.
The key to the bloom’s initiation lies in the composition of volcanic ash. "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," explained Professor Karl. Iron is a crucial micronutrient for phytoplankton, often limiting their growth in the open ocean. Volcanic ash, rich in bioavailable iron, effectively provides the missing ingredient needed to unlock the photosynthetic potential of these microscopic organisms.
A Natural Carbon Sequestration Event
The implications of this phytoplankton bloom extend beyond its sheer size and ecological significance. The rapid proliferation of phytoplankton led to the production of a substantial amount of organic matter. As these organisms complete their life cycles and sink to the deep ocean, they effectively remove organic carbon from the surface waters and atmosphere, a process known as carbon export. This natural mechanism plays a vital role in the ocean’s carbon cycle.
"Our estimates are that export of organic carbon may be equivalent to about half of the carbon dioxide initially released from the eruption," Professor Karl elaborated. "This marine carbon dioxide sequestration is a natural process that probably occurs whenever volcanic eruptions inject ash into the atmosphere and carry that particulate matter out to sea. The combination of ash deposition and the nutrient-starved conditions in our study area aligned to create a massive bloom that was easily seen by satellite remote sensing and Argo floats that had been previously deployed in that region."
The study’s findings suggest that such ash-induced phytoplankton blooms could represent a significant, albeit intermittent, natural carbon sink. The magnitude of this sequestration, potentially offsetting a substantial portion of the volcano’s carbon dioxide emissions, underscores the complex interplay between geological events and the Earth’s climate system.
Broader Implications for Oceanography and Climate Science
This research provides a critical empirical demonstration of how distant volcanic events can exert a profound influence on remote oceanic ecosystems. It highlights the interconnectedness of Earth’s systems and the potential for seemingly localized phenomena to have far-reaching global consequences.
The findings have several key implications:
- Refining Phytoplankton Bloom Models: The study offers valuable data for improving predictive models of phytoplankton bloom dynamics, particularly in nutrient-limited oceanic regions. Understanding the triggers and drivers of such large-scale blooms is crucial for accurately assessing primary productivity and its impact on marine food webs.
- Enhancing Carbon Cycle Understanding: The research provides concrete evidence of a natural carbon sequestration pathway linked to volcanic activity. This contributes to a more comprehensive understanding of the ocean’s role in regulating atmospheric carbon dioxide levels, a critical factor in climate change research.
- Monitoring Volcanic Impacts: The study demonstrates the utility of satellite remote sensing in tracking the environmental impacts of volcanic eruptions, even at vast distances. This can inform future monitoring strategies and disaster response efforts.
- Assessing Ecosystem Resilience: The ability of the North Pacific Subtropical Gyre to host such a massive bloom, albeit triggered by external inputs, offers insights into the resilience and adaptive capacity of marine ecosystems.
Future Research and Monitoring
The research team is keen to build upon these findings. The experience gained from studying the 2018 Kīlauea event has prepared them to monitor future volcanic eruptions and their subsequent effects on phytoplankton blooms. The possibility of another major eruption of this magnitude is a catalyst for enhanced preparedness.
"If another major eruption occurs, they plan to deploy a research vessel to study the bloom’s development and response in real-time," stated Professor Karl. Such direct in-situ observations would provide invaluable ground-truth data to complement satellite measurements, allowing for a more detailed and nuanced understanding of the bloom’s progression, its ecological impacts, and its efficiency in sequestering carbon.
This collaborative effort, spanning institutions across Hawaiʻi, Malaysia, and Taiwan, exemplifies the power of international scientific cooperation in tackling complex global challenges. The study’s publication in JGR Oceans marks a significant step forward in our understanding of the intricate relationships that govern our planet’s oceans and atmosphere, revealing how even the most dramatic geological events can trigger unexpected and vital biological responses in the vast, blue expanse. The legacy of Kīlauea’s 2018 eruption, therefore, extends far beyond the immediate terrestrial impact, reaching into the very heart of the ocean’s biological engine.