Nitrogen isotope fractionation explains the 15N enrichment of Antarctic cryptogams by volatilized ammonia from penguin and seal colonies

Bokhorst, Stef; van Logtestijn, Richard; Convey, Peter ORCID: https://orcid.org/0000-0001-8497-9903; Aerts, Rien. 2019 Nitrogen isotope fractionation explains the 15N enrichment of Antarctic cryptogams by volatilized ammonia from penguin and seal colonies. Polar Research, 38, 3355. https://doi.org/10.33265/polar.v38.3355

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Abstract/Summary

Vegetation near bird and seal rookeries typically has high δ15N signatures and these high values are linked to the enriched δ15N values of rookery soils. However, Antarctic cryptogams are mostly dependent on atmospheric ammonia (NH3) and volatized NH3 from rookeries is severely depleted in δ15N-NH3. So there is an apparent discrepancy between the isotopically depleted source (NH3) and δ15N-enriched vegetation. In this article, we aim to resolve this discrepancy to better understand the mechanisms and processes involved in isotopic changes during nitrogen transfer between Antarctic marine and terrestrial ecosystems. Under laboratory conditions, we quantified whether volatized NH3 affects the isotopic signature of cryptogams. NH3 volatilizing from penguin guano and elephant seal dung was depleted (44–49‰) in δ15N when captured on acidified filters, compared to the source itself. Cryptogams exposed to the volatized NH3 were enriched (18.8–23.9‰) in δ15N. The moss Andreaea regularis gained more nitrogen (0.9%) than the lichen Usnea antarctica (0.4%) from volatilized NH3, indicating a potential difference in atmospheric NH3 acquisition that is consistent with existing field differences in nitrogen concentrations and δ15N between mosses and lichens in general. This study clarifies the δ15N enrichment of cryptogams resulting from one of the most important nitrogen pathways for Antarctic vegetation.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.33265/polar.v38.3355
ISSN:	0800-0395
Additional Keywords:	lichen, Moss, nitrogen pathway, nutrient transfer, ocean-land interaction
Date made live:	26 Nov 2019 13:17 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/519906

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.33265/polar.v38.3355

ISSN:

0800-0395

Additional Keywords:

lichen, Moss, nitrogen pathway, nutrient transfer, ocean-land interaction

Date made live:

26 Nov 2019 13:17 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/519906