MEPS 488:81-88 (2013)  -  DOI: https://doi.org/10.3354/meps10403

Geochemical evidence of oceanic iron fertilization by the Kasatochi volcanic eruption in 2008 and the potential impacts on Pacific sockeye salmon

N. Olgun1,2,7,*, S. Duggen3, B. Langmann4, M. Hort4, C. F. Waythomas5, L. Hoffmann2, P. Croot

1Dynamics of the Ocean Floor Division, Helmholtz Centre for Ocean Research Kiel (GEOMAR), 24105 Kiel, Germany
2Marine Biogeochemistry Division, Helmholtz Centre for Ocean Research Kiel, (GEOMAR), 24148 Kiel, Germany
3A. P. Møller Skolen, Upper Secondary School and Sixth Form College of the Danish National Minority in Northern Germany,
24837 Schleswig, Germany
4Institute of Geophysics, University of Hamburg, Klima Campus, 20146 Hamburg, Germany
5US Geological Survey Alaska Volcano Observatory, Anchorage, Alaska 99508, USA
6Earth and Ocean Sciences Department, National University of Ireland, Galway, Ireland
7Present address: Eurasia Institute of Earth Sciences, Istanbul Technical University, 34469 Istanbul, Turkey

ABSTRACT: The Kasatochi volcanic eruption that occurred in the central Aleutian Islands in Alaska, USA, in August 2008 is thought to have induced a massive diatom bloom in the iron-limited waters of the Gulf of Alaska, which potentially affected the oceanic food web by increasing the abundance of zooplankton and sockeye salmon Oncorhynchus nerka in the northeast Pacific Ocean. We report the first seawater experiments involving volcanic ash ejected from the Kasatochi eruption, showing that the ash released 61 to 83 nmol Fe, 374 to 410 nmol NO3-, 5 to 6 nmol PO43- and 170 to 585 nmol SiO2 when it contacted seawater. Our study suggests that the amount of iron released from Kasatochi ash (an increase of 2.0 to 2.8 nM Fe) was indeed sufficient to cause the observed phytoplankton bloom in the northeastern Pacific Gyre, while the impact of macronutrient release was minimal. We further evaluated the multiple, interdependent processes in the oceanic food web related to the diatom bloom, involving the ocean survival of juvenile salmon that entered the northeast Pacific Ocean in the summer of 2008.


KEY WORDS: Kasatochi eruption · Volcanic ash · Fe limitation · Diatom bloom · Gulf of Alaska · Sockeye salmon


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Cite this article as: Olgun N, Duggen S, Langmann B, Hort M, Waythomas CF, Hoffmann L, Croot P (2013) Geochemical evidence of oceanic iron fertilization by the Kasatochi volcanic eruption in 2008 and the potential impacts on Pacific sockeye salmon. Mar Ecol Prog Ser 488:81-88. https://doi.org/10.3354/meps10403

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