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

  • Stef Bokhorst Department of Ecological Science, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
  • Richard van Logtestijn Department of Ecological Science, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
  • Peter Convey British Antarctic Survey, Natural Environment Research Council, High Cross, Cambridge, UK
  • Rien Aerts Department of Ecological Science, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
Keywords: lichen, Moss, nitrogen pathway, nutrient transfer, ocean-land interaction


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.


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How to Cite
Bokhorst S., van Logtestijn R., Convey P., & Aerts R. (2019). Nitrogen isotope fractionation explains the <sup>15</sup&gt;N enrichment of Antarctic cryptogams by volatilized ammonia from penguin and seal colonies. Polar Research, 38.
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