ORCID

Abstract

Alkylamines, volatile organic nitrogen compounds with low molecular weight, are present in the surface ocean and participate in the marine biogeochemical nitrogen cycle, atmospheric chemistry and cloud formation. Alkylamines have been detected in polar regions, suggesting that these areas constitute emission hotspots of these compounds. However, knowledge of the sea surface distribution patterns and factors modulating alkylamines remain limited due to their high reactivity and low concentrations, which hamper accurate measurements. We investigated the presence and distribution of alkylamines in seawaters around the Antarctic Peninsula and the northern Weddell Sea during the late austral summer and explored their potential links to marine microbiota. Alkylamines were ubiquitous in all analysed samples, accounting for ∼ 2 % of the dissolved and particulate organic nitrogen pool. The only particulate form found was trimethylamine (TMA), detected for the first time in Antarctic waters at concentrations of 9.7 ± 4.6 nM. We efficiently measured dissolved trimethylamine (TMA, 20.9 ± 15.2 nM), dimethylamine (DMA, 32.3 ± 32.7 nM) and diethylamine (DEA, 7.2 ± 1.7 nM) across the surveyed area, while dissolved monomethylamine (MMA, 12.7 ± 0.1 nM) remained below the detection limit in most samples. Variations in alkylamine concentrations did not align with the overall phytoplankton biomass but with specific biological components. TMA was predominantly associated with, and released from, nanophytoplankton. DMA was likely produced by the degradation of TMA or trimethylamine oxide by nanophytoplankton cells or associated heterotrophic bacteria. The sources of DEA remain unclear but were suggestive of a distinct biogeochemical pathway from those of TMA and DMA. MMA is thought to primarily originate from bacterial degradation of nitrogen-based osmolytes or amino acids, but detection in too few samples precluded any robust association with microbiota. This study reveals that volatile alkylamines are widespread in Antarctic surface waters, where they are primarily sourced from nanophytoplankton cells and associated heterotrophic bacteria and protists.

Publication Date

2025-07-15

Publication Title

Biogeosciences

Volume

22

Issue

13

ISSN

1726-4170

Acceptance Date

2025-05-05

Deposit Date

2025-08-14

First Page

3429

Last Page

3448

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