By Lina carolina 
The explosive May 2018 eruption of Kīlauea Volcano on Hawaiʻi Island, one of the most significant in over two centuries, not only reshaped the island’s landscape but also triggered a colossal, unprecedented phytoplankton bloom in the North Pacific Subtropical Gyre. This massive bloom, stretching across an area of oceanic expanse and lasting for an extended period, was directly linked to volcanic ash deposited approximately 1,200 miles west of the eruption site. The groundbreaking findings, published recently in the esteemed journal JGR Oceans, reveal a profound and previously underestimated connection between terrestrial volcanic activity and distant marine ecosystems, offering critical insights into oceanographic processes and the global carbon cycle.
A Cascade of Ash and Algae
The Kīlauea eruption, which commenced in early May 2018 and continued for several months, was characterized by its immense scale. The volcano spewed an enormous quantity of ash into the atmosphere, forming a plume that soared nearly five miles high. This ash, rich in essential nutrients like iron, became the unlikely catalyst for a significant biological event thousands of miles away.
"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 a distinguished professor at the University of Hawaiʻi (UH) at Mānoa’s Center for Microbial Oceanography: Research and Education. "Our study unequivocally demonstrates the connection between the eruption of Kīlauea and bloom formation far from the volcano. This has profound implications for refining our understanding of phytoplankton bloom dynamics and enhancing our comprehension of the ocean’s carbon cycle."
While Kīlauea is recognized as one of the world’s most active volcanoes, with a history of multiple eruptions over the past four decades, its volcanic ash had not previously been definitively linked to large-scale open ocean phytoplankton blooms. The 2018 eruption, however, was exceptional in its magnitude, releasing millions of cubic feet of molten lava into the Pacific waters off the Big Island and injecting an estimated 50 kilotons of sulfur dioxide and approximately 77 kilotons of carbon dioxide into the atmosphere daily.
Tracing the Ash’s Journey
The journey of the volcanic ash from Kīlauea to the distant North Pacific is a testament to the power of atmospheric circulation. Prevailing winds, a constant force in the region, efficiently transported the fine ash particles westward across the vast expanse of the Pacific Ocean.
"After the 2018 eruption, the prevailing winds transported ash particles to the west," explained Wee Cheah, the study’s corresponding author and Senior Lecturer at Universiti Malaya’s Institute of Ocean and Earth Sciences. "The trajectories of the ash were meticulously recorded by Earth-orbiting satellites that are capable of detecting changes in the optical clarity of the atmosphere, a phenomenon known as aerosol optical depth. The eventual fallout of this ash into the surface ocean was dictated by factors such as the density, size, and shape of the particulate matter, as well as prevailing atmospheric conditions, particularly rainfall, which can accelerate deposition."
The research team, led by Chun Hoe Chow, Associate Professor in the Department of Marine Environmental Informatics at the National Taiwan Ocean University, employed a multifaceted approach to reconstruct this remarkable event. They not only tracked the atmospheric transport of ash using satellite data but also utilized remote sensing of ocean color. Ocean color, a proxy for phytoplankton concentration, revealed the emergence of a massive bloom near the International Date Line, a region not typically associated with such extensive algal growth, especially during the summer months.
A Nutrient-Rich Anomaly in the Ocean Desert
The North Pacific Subtropical Gyre, where the bloom occurred, is often described as an oceanic desert. Its surface waters are characteristically nutrient-depleted, making it challenging for phytoplankton to thrive. However, the arrival of volcanic ash introduced a critical missing ingredient.
"The waters in the open ocean of the Pacific are nutrient depleted, and the addition of volcanic ash, particularly iron contained within it, and to a lesser extent other trace elements and possibly phosphate, can stimulate the growth of marine phytoplankton," Professor Karl elaborated. "This is especially true for the so-called nitrogen-fixing microbes, which can proliferate even in the absence of additional nitrogen."
Iron is a vital micronutrient for marine life, playing a crucial role in photosynthesis and nitrogen fixation. Volcanic ash, a complex mixture of minerals, is a natural source of iron. The sheer volume of ash deposited in 2018 provided a substantial nutrient boost to the otherwise oligotrophic waters, triggering a cascade of biological activity.
The Carbon Cycle Connection: From Bloom to Sequestration
The proliferation of phytoplankton in the North Pacific led to the creation of a vast amount of organic matter. As these microscopic organisms lived out their life cycles, they eventually died and began to sink to the deeper ocean. This process, known as export production, plays a critical role in the ocean’s carbon cycle by effectively removing organic carbon from the surface layer and sequestering it in the deep sea.
"Our estimates suggest that the export of organic carbon may be equivalent to about half of the carbon dioxide initially released from the eruption," Professor Karl revealed. "This marine carbon dioxide sequestration is a natural process that likely occurs whenever volcanic eruptions inject ash into the atmosphere and transport that particulate matter out to sea. The confluence of ash deposition and the nutrient-starved conditions in our study area created a perfect storm for a massive bloom that was readily detectable by satellite remote sensing and Argo floats previously deployed in that region."
The implications of this natural carbon sequestration are significant. Volcanic eruptions, while destructive in their immediate vicinity, can also trigger natural processes that help mitigate some of the greenhouse gas emissions they release. This study highlights the complex feedback loops within Earth’s systems and underscores the need for comprehensive monitoring of volcanic impacts on ocean ecosystems.
A Chronology of the Event
May 2018: The Kīlauea Volcano on Hawaiʻi Island erupts explosively, sending a massive plume of ash and gases into the atmosphere.
May – August 2018: Prevailing winds carry volcanic ash westward across the Pacific Ocean. Satellite imagery tracks the dispersal of atmospheric aerosols.
Summer 2018: A significant phytoplankton bloom begins to form in the North Pacific Subtropical Gyre, approximately 1,200 miles west of Kīlauea. This bloom is detected through satellite observations of ocean color.
Ongoing: Researchers from an international team, including institutions in the United States, Malaysia, and Taiwan, begin analyzing satellite data and oceanographic information to understand the cause of the bloom.
Recent Publication: A study detailing the connection between the Kīlauea eruption ash and the North Pacific phytoplankton bloom is published in JGR Oceans.
Broader Implications and Future Research
This research offers crucial insights into the interconnectedness of Earth’s systems and the far-reaching consequences of major geological events. The findings have several important implications:
- Understanding Phytoplankton Dynamics: The study refines our understanding of the factors that trigger and sustain phytoplankton blooms, particularly in nutrient-limited oceanic regions. It highlights the potential role of volcanic ash as a significant nutrient source.
- Ocean Carbon Cycle: The research quantifies the amount of carbon sequestered through this volcanically-induced bloom, providing valuable data for global carbon cycle models. This natural process of carbon removal from the atmosphere and upper ocean could be a significant, albeit unpredictable, component of Earth’s carbon budget.
- Remote Sensing Applications: The study validates the effectiveness of satellite remote sensing in detecting and monitoring large-scale oceanographic events, even those triggered by distant terrestrial phenomena.
- Predictive Capabilities: By understanding the mechanisms at play, scientists may be able to better predict the potential ecological impacts of future volcanic eruptions.
The research team is already looking ahead. They are prepared to monitor future volcanic eruptions and their potential effects on phytoplankton blooms. Should another major eruption occur, they are planning to deploy a research vessel to study the bloom’s development and ecological response in real-time, providing unprecedented in-situ data to complement satellite observations. This proactive approach will further enhance our ability to unravel the intricate relationships between volcanic activity, ocean ecosystems, and the global climate. The legacy of the 2018 Kīlauea eruption extends far beyond the shores of Hawaiʻi, reminding us of the dynamic and interconnected nature of our planet.
