Comparison between silicon and nitrogen isotopes in the upwelling area off Peru.

Grasse, Patricia , Ryabenko, Evgeniya, Ehlert, Claudia and Frank, Martin (2012) Comparison between silicon and nitrogen isotopes in the upwelling area off Peru. [Poster] In: 2012 Ocean Sciences Meeting, OSM. , 20.02.-24.02.2012, Salt Lake City, Utah, USA . 2012 Ocean Sciences Meeting : abstract book ; February 20-24. 2012 ; Salt Palace Convention Center, Salt Lake City, Utah, USA. ; ID 10946 .

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Abstract

Abstract ID: 10946
PosterID: B1569
In this study we present the first direct comparison between dissolved stable silicon (δ³⁰Si(OH)₄) and nitrogen (δ¹⁵NO₃-) isotopes in the upwelling area off Peru to investigate biogeochemical processes and nutrient cycling in one of the globally largest Oxygen Minimum Zones (OMZ). Silicon and nitrogen isotopes in the euphotic zone of the open ocean are mainly influenced by utilization in the way that diatoms preferentially incorporate the lighter isotopes, whereas in regions with prevailing anoxic waters the nitrate isotope composition is also altered by other processes. Silicic acid limitation offshore is indicated by high NO₃-:Si(OH)₄ ratios (~15) leading to the highest δ³⁰Si(OH)₄ values (3.7‰) accompanied by high δ¹⁵NO₃- values (16‰). Due to upwelling and intense recycling of silicic acid on the shelf, surface samples show low δ³⁰Si(OH)₄ values around 2‰. Nitrate isotope compositions in surface waters differ from values expected from δ³⁰Si(OH)₄ suggesting that either N-loss (denitrification and/or anammox) processes cause enrichment of heavy N-isotopes in the source waters of the upwelling, or the utilization of different N species derived from N₂-fixation or the utilization of ammonia occurs.

Document Type: Conference or Workshop Item (Poster)
Keywords: Oceanography; Biogeochemistry; Silicon; nitrogen; Pacific Ocean; Peru
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
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Date Deposited: 12 Apr 2012 12:02
Last Modified: 13 Apr 2012 04:05
URI: http://oceanrep.geomar.de/id/eprint/14197

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