Journal Article

Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean

Moffett, James W., Resing, Joseph A., German, Christopher R., Jenkins, William J., Tagliabue, Alessandro, Sedwick, Peter N., Sohst, Bettina M.

2015

Overview

Hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise is transported several thousand kilometres westward across the South Pacific Ocean; global hydrothermal dissolved iron input is estimated to be more than four times what was previously thought and modelling suggests it must be physically or chemically stabilized in solution. Trans-Pacific transport of hydrothermal metals Deep-sea hydrothermal vents are an important source of iron, an essential trace element that can limit marine productivity. Recent studies have questioned the long-standing view that most of the iron discharged from such vents is removed from seawater close to its source, and is therefore of limited importance for ocean biogeochemistry. Joseph Resing et al . report on the lateral transport of hydrothermal dissolved iron and other trace metals from the southern East Pacific Rise more than 4,000 km across the South Pacific Ocean. Using data from samples collected from 35 hydrographic stations between Manta, Ecuador and Papeete, Tahiti, the authors estimate an input of global hydrothermal dissolved iron to the ocean at least four times greater than previously reported. With the help of a model study, they suggest that physicochemical stabilization of iron enables hydrothermal activity to significantly affect the carbon cycle by supporting phytoplankton growth in the Southern Ocean. Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean 1 , 2 , 3 . Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle 4 . It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources 2 , 5 and is thus of limited importance for ocean biogeochemistry 6 . This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport 7 , 8 , 9 , 10 . Such transport has been subsequently inferred from spatially limited oceanographic observations 11 , 12 , 13 . Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed 6 , 14 . Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates 7 , 11 , 14 . Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 704/106/829/827 / 704/172/169/827 / Aluminum / Biogeochemistry / Chemical oceanography / Chemical properties / Environmental aspects / Humanities and Social Sciences / Hydrothermal Vents - chemistry / Iron / letter / Manganese / Metallic elements / Metals - chemistry / Models, Theoretical / multidisciplinary / Oceans / Pacific Ocean / Primary production / Science / Seawater / Seawater - chemistry / Trace elements / Water Movements