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Spatial patterns of benthic silica flux in the North Pacific reflect upper ocean production

Hou, Yi and Hammond, Douglas E. and Berelson, William M. and Kemnitz, Nathaniel and Adkins, Jess F. and Lunstrum, Abby (2019) Spatial patterns of benthic silica flux in the North Pacific reflect upper ocean production. Deep Sea Research Part 1, 148 . pp. 25-33. ISSN 0967-0637. doi:10.1016/j.dsr.2019.04.013.

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Diatoms are the dominant algal group that cycles dissolved silicic acid in the ocean; they also play an important role in the oceanic carbon cycle. It is therefore important to quantify the spatial distribution of silica cycling for defining global ocean biogeochemical cycles. On the research cruise CDisK-IV, water samples and sediment cores were collected at 5 stations along a North Pacific transect near 150ºW from 22ºN to 50ºN to evaluate benthic remineralization rates of biogenic silica (bSi). Two independent methods, core incubation and diffusive transport based on porewater profiles, were utilized to estimate benthic silicic acid fluxes, and these independent methods yield fluxes that agree within uncertainties. The benthic fluxes are reported as 0.04 ± 0.01, 0.04 ± 0.01, 0.05 ± 0.01, 0.67 ± 0.14, 0.40 ± 0.08 mmol Si m^(−2) day^(−1) for Stations 1 to 5, south to north, respectively. Burial fluxes were estimated using measurements of solid phase bSi in sediments and literature values of sediment accumulation rate. Burial efficiencies of bSi at all stations were <5% and show reasonable agreement with previous estimates. When burial rates were added to benthic fluxes to calculate rain rates, the rain observed under the subarctic gyre (Stations 4–5), was far larger than in the lower latitudes of the subtropics (Stations 1–3), corresponding to higher surface diatom productivity at higher latitudes. At the two northern stations, the bottom 500 m of the water column shows a near-bottom increase in silicic acid that is consistent with the measured benthic flux and the estimated vertical eddy diffusivity. Above this horizon, water column density stratification increases and vertical diffusivity decreases, but the silicic acid gradient decreases. This reduction in gradient indicates that above this horizon, horizontal transport by deep waters, rather than vertical diffusion, becomes the dominant process removing the silicic acid released by benthic remineralization.

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Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2019 Elsevier Ltd. Received 9 August 2018, Revised 12 April 2019, Accepted 22 April 2019, Available online 24 April 2019.
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Record Number:CaltechAUTHORS:20190424-111734892
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Official Citation:Yi Hou, Douglas E. Hammond, William M. Berelson, Nathaniel Kemnitz, Jess F. Adkins, Abby Lunstrum, Spatial patterns of benthic silica flux in the North Pacific reflect upper ocean production, Deep Sea Research Part I: Oceanographic Research Papers, Volume 148, 2019, Pages 25-33, ISSN 0967-0637, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94932
Deposited By: Tony Diaz
Deposited On:24 Apr 2019 18:22
Last Modified:16 Nov 2021 17:08

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