Volcano-stimulated marine photosynthesis

Marine phytoplankton, microscopic unicellular algae, are responsible for about half of the photosynthesis on Earth (1). Photosynthesis, on land and sea, maintains atmospheric oxygen and CO2 levels, governing the habitability of the planet. This ocean photosynthesis (called primary production) is supported by opposing physical oceanographic mechanisms. Vertical stability, or buoyancy, of the ocean surface layer maintains the photosynthesizing biomass in the solar-irradiated euphotic zone, whereas vertical mixing or upwelling supplies deepwater nutrients, such as nitrogen, phosphorus, and silicon, which are required for phytoplankton growth. On page 1040 of this issue, Wilson et al. (2) report a heretofore unknown mechanism that enhances primary production of organic matter off Hawai’i. They found that lava discharged into the ocean by the erupting Kīlauea volcano created a plume of increased nutrient concentrations, enhanced phytoplankton growth, increased plankton abundance, and altered plankton species composition. Any of these responses could alter the local carbon cycle.

By Hugh Ducklow, et al.

Sep 6th, 2019

Kīlauea lava fuels phytoplankton bloom in the North Pacific Ocean

From June to August 2018, the eruption of Kīlauea volcano triggered a diatom-dominated phytoplankton bloom. Wilson et al. set sail to sample the plume, deploying subsea gliders and using satellite monitoring to measure the dynamics of this rare event in the nutrient-poor Pacific (see the Perspective by Ducklow and Plank). They found subsurface chlorophyll maxima not visible by remote sensing, performed transcriptome and N isotope marker analysis, and measured nutrients, partitioning of biomass into different organisms, and primary production. Much of the data are corroborated by physical modeling of the ocean dynamics. The authors conclude that the plume was fed by the lava heating subsurface water and triggering upwelling of deepwater nutrients to the surface rather than by direct injection of micronutrients from lava.

By Stephanie Dutkiewicz, et al.

Sep 6th, 2019