Subduction zone volcanic ash can fertilize the surface ocean and stimulate phytoplankton growth: Evidence from biogeochemical experiments and satellite data

Abstract

[1] Volcanoes confront Earth scientists with new fundamental questions: Can airborne volcanic ash release nutrients on contact with seawater, thereby excite the marine primary productivity (MPP); and, most notably, can volcanoes through oceanic fertilization affect the global climate in a way that is so far poorly understood? Here we present results from biogeochemical experiments showing that 1) volcanic ash from subduction zone volcanoes rapidly release an array of nutrients (co-)limiting algal growth in vast oceanic areas, 2) at a speed much faster (minute-scale) than hitherto known and that marine phytoplankton from low-iron oceanic areas can swiftly, within days, utilize iron from volcanic sources. We further present satellite data possibly indicating an increase of the MPP due to the seaward deposition of volcanic particulate matter. Our study supports the hypothesis that oceanic (iron) fertilization with volcanic ash may play a vital role for the development of the global climate. Citation: Duggen, S., P. Croot, U. Schacht, and L. Hoffmann (2007), Subduction zone volcanic ash can fertilize the surface ocean and stimulate phytoplankton growth: Evidence from biogeochemical experiments and satellite data,

Origin and significance of ice‐rafted detritus in the Atlantic sector of the Southern Ocean

“…Tephra is an especially efficient source of nutrients, as soluble coatings on the glass grains from the erupted gasses are released quickly into the water column upon settling [Frogner et al, 2001;Duggen et al, 2007]. During the last glacial period when sea ice was more extensive sea, the deposition of dust and Ferich volcanic sediment on sea ice may have facilitated high primary production [Moore et al, 2000].…”

Volcano impacts on climate and biogeochemistry in a coupled carbon–climate model

“…Some authors argue that the additional nutrients and trace elements added to the ocean may be responsible for additional carbon uptake (e.g., Watson, 1997;Frogner et al, 2001;Duggen et al, 2007Duggen et al, , 2010, but a quantitative assessment of this effect on global carbon or ocean productivity has not yet been performed. The strength at which land and ocean sinks reduce atmospheric CO 2 is not increasing at the same rate as anthropogenic emissions are increasing (Le Quéré et al, 2009;Sarmiento et al, 2010), as evidenced by an increase in atmospheric CO 2 levels.…”

Early response of the northeast subarctic Pacific plankton assemblage to volcanic ash fertilization

“…Volcanic ash also represents a potential source of Fe for the ocean (Spirakis 1991), but very few studies have been conducted to determine its significance (Olgun et al 2011). Recent investigations have shown a rapid (within minutes) release of Fe following the contact of volcanic ash with water, a release comparable to that of terrestrially derived dust (Duggen et al 2007;Jones and Gislason 2008;Olgun et al 2011). Calculations made by Olgun et al (2011) suggest that since the last glacial maximum and on time scales approaching 1000 yr, ash flux to the Pacific Ocean is comparable to the atmospheric flux of dust from the continents.…”

“…However, the response of phytoplankton to ash deposition remains largely unconstrained. The few laboratory studies conducted so far have shown a variety of responses, from a stimulation of phytoplankton growth to a toxic effect (Duggen et al 2007;Hoffmann et al 2012).…”