FN Archimer Export Format
PT J
TI Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads
BT 
AF Ng, Hong Chin
   Hawkings, Jon R.
   Bertrand, Sebastien
   Summers, Brent A.
   Sieber, Matthias
   Conway, Tim M.
   Freitas, Felipe S.
   Ward, James P.J.
   Pryer, Helena V.
   Wadham, Jemma L.
   Arndt, Sandra
   Hendry, Katharine R.
AS 1:1,2;2:3;3:4;4:5;5:5;6:5;7:1,6;8:1;9:7,8;10:7,9;11:6;12:1,10;
FF 1:;2:;3:;4:;5:;6:;7:;8:;9:;10:;11:;12:;
C1 School of Earth Sciences University of Bristol Bristol, UK
   Ifremer, Université Bretagne Occidentale, CNRS, Geo‐Ocean 29280 Plouzané ,France
   Department of Earth and Environmental Science University of Pennsylvania Philadelphia ,USA
   Renard Centre of Marine Geology Ghent University Gent, Belgium
   College of Marine Science University of South Florida St Petersburg FL, USA
   BGeosys, Department of Geosciences Université libre de Bruxelles BrusselsCP160/03 1050, Belgium
   Bristol Glaciology Centre School of Geographical Sciences University of Bristol Bristol ,UK
   Department of Earth Sciences University of Cambridge Cambridge ,UK
   Centre for Arctic Gas Hydrate Environment and Climate (CAGE) Department of Geosciences UiT The Arctic University of Norway N‐9037 Tromsø, Norway
   Polar Oceans Team British Antarctic Survey Cambridge, UK
C2 UNIV BRISTOL, UK
   UBO, FRANCE
   UNIV PENNSYLVANIA, USA
   UNIV GHENT, BELGIUM
   UNIV S FLORIDA, USA
   UNIV LIBRE BRUXELLES, BELGIUM
   UNIV BRISTOL, UK
   UNIV CAMBRIDGE, UK
   UNIV ARCTIC UIT NORWAY, NORWAY
   BRITISH ANTARCTIC SURVEY (BAS), UK
UM GEO-OCEAN
IN WOS Cotutelle UMR
   copubli-europe
   copubli-int-hors-europe
IF 5.2
TC 2
UR https://archimer.ifremer.fr/doc/00805/91747/97707.pdf
   https://archimer.ifremer.fr/doc/00805/91747/97708.pdf
   https://archimer.ifremer.fr/doc/00805/91747/97709.xlsx
LA English
DT Article
DE ;fjord biogeochemistry;sediment nutrient cycling;silicon and iron;stable isotopes;early diagenesis;reaction transport modeling
AB Glacier meltwater supplies silicon (Si) and iron (Fe) sourced from weathered bedrock to downstream ecosystems. However, the extent to which these nutrients reach the ocean is regulated by the nature of the benthic cycling of dissolved Si and Fe within fjord systems, given the rapid deposition of reactive particulate fractions at fjord heads. Here, we examine the benthic cycling of the two nutrients at four Patagonian fjord heads through geochemical analyses of sediment pore waters, including Si and Fe isotopes (δ30Si and δ56Fe), and reaction-transport modeling for Si. A high diffusive flux of dissolved Fe from the fjord sediments (up to 0.02 mmol m-2 day-1) compared to open ocean sediments (typically <0.001 mmol m-2 day-1) is supported by both reductive and non-reductive dissolution of glaciallysourced reactive Fe phases, as reflected by the range of pore water δ56Fe (-2.7 to +0.8‰). In contrast, the diffusive flux of dissolved Si from the fjord sediments (0.02–0.05 mmol m-2 day- 1) is relatively low (typical ocean values are >0.1 mmol m-2 day-1). High pore water δ30Si (up to +3.3‰) observed near the Fe(II)-Fe(III) redox boundary is likely associated with the removal of dissolved Si by Fe(III) mineral phases, which, together with high sedimentation rates, contribute to the low diffusive flux of Si at the sampled sites. Our results suggest that early diagenesis promotes the release of dissolved Fe, yet suppresses the release of dissolved Si at glaciated fjord heads, which has significant implications for understanding the downstream transport of these nutrients along fjord systems. Plain Language Summary Through physical grinding and chemical reactions, glaciers are capable of releasing nutrients such as silicon and iron from the underlying rocks. In particular, there is a growing interest in the supply of these glacier-sourced nutrients to sustain the growth of marine life in highlatitude estuaries (fjords) and the adjacent coastal ocean. However, a substantial portion of the glacier-sourced nutrients may be removed by rapid settling of debris (sediments) at the heads of these fjords, before they can be used by marine life. This study analyzes the chemistry of fluids within sediments collected from Patagonian fjord near river and glacial inputs to investigate the fate of glacier-sourced nutrients (silicon and iron) that have been transferred to the fjord floor. Our laboratory analysis and calculations reveal that biological, chemical and geological processes in these sediments release significant amounts of iron back into the overlying fjord waters, but these high levels of iron chemically bind silicon, restricting its release into fjord waters. The disproportionate release of the two nutrients from fjord sediments found in this study advances our understanding of the modes of supply of glacier-sourced nutrients to fjords and the coastal ocean 
PY 2022
PD NOV
SO Global Biogeochemical Cycles
SN 0886-6236
PU American Geophysical Union (AGU)
VL 36
IS 11
UT 000934035100001
DI 10.1029/2022GB007493
ID 91747
ER

EF