Determination of picomolar dissolved free amino acids along a South Atlantic transect using reversed-phase high-performance liquid chromatography.

Sabadel, A. J. M., Browning, Thomas J., Kruimer, D., Airs, R. L., Woodward, E. M. S., Van Hale, R. and Frew, R. D. (2017) Determination of picomolar dissolved free amino acids along a South Atlantic transect using reversed-phase high-performance liquid chromatography. Marine Chemistry, 196 . pp. 173-180. DOI 10.1016/j.marchem.2017.09.008.

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Abstract

Dissolved free amino acids (DFAA) in seawater are a form of nitrogen (N) available for marine microbes. In oligotrophic environments where N-containing nutrients are the limiting factor for microbial growth, N nutrition from DFAA could be crucial, but as yet it is poorly resolved. Measurements of individual DFAA are challenging as concentrations are typically in the low nmol L− 1 range. Here we report modifications to methodology using o-phthaldialdehyde (OPA) derivatization and reversed phase high performance liquid chromatography (HPLC) that provide a 30-fold improvement in sensitivity enabling the detection of 15 amino acids in seawater with a limit of detection as low as 10 pmol L− 1 with accuracy and precision of better than 10%. This analytical methodology is now suitable for the challenging quantitation of DFAA in oligotrophic seawaters. The method was successfully applied to a suite of seawater samples collected on a cruise crossing the South Atlantic Ocean, where concentrations of DFAAs were generally low (sub nmol L− 1), revealing basin-scale features in the oceanographic distributions of DFAA. This unique dataset implies that DFAAs are an important component of the N cycle in both near-coastal and open oceans. Further calculations suggest that the proportions of organic N originating from DFAA sources were significant, contributing between 0.2 and 200% that of NH4 + and up to 77% that of total inorganic nitrogen in the upper 400 m in some regions of the transect.

Document Type: Article
Keywords: amino aciddissolved matterlimiting factorliquid chromatography, marine environment, nutrient dynamics, oligotrophic environment, open ocean, performance assessment, seawater, transect, South Atlantic Ocean
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.marchem.2017.09.008
ISSN: 0304-4203
Projects: UK-GEOTRACES
Date Deposited: 20 Nov 2017 10:04
Last Modified: 01 Feb 2019 15:03
URI: http://oceanrep.geomar.de/id/eprint/40169

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