Phosphatization under birds’ activity : ornithogenesis at different scales on Antarctic Soilscapes.

Abstract

Extensive areas of penguins’ nesting (Pygoscelis sp.), on ice-free areas, account for vast deposits of organic matter- rich guano in maritime Antarctica. One such area, at Harmony Point, currently houses different penguin colonies

with extensive and unique ornithogenic soils, where phosphatization is the key soil-forming process. We sought

to enhance the knowledge of phosphatization process, products, cycles, and phosphorus (P) forms in these un- usual soils. We compared ornithogenic and non-ornithogenic soils, based on advanced chemical, micromor- phological and mineralogical analyses of samples of guano and phosphate biocrusts, complete with P and OM

fractionation. Ornithogenic soils have the organic P-pool as the largest phosphorous compartment, followed by varying P-Ca forms. In contrast, soils unaffected by phosphatization showed a high inorganic P-pool. Penguin

guano is enriched with P, Ca, K, Cu, Zn, C and N. The phosphatic biocrusts are composed of struvite and hy- droxyapatite, forming a gradient of phosphate forms. We recognized three different phosphatization environ- ments, namely (i) present-day marine birds’ rookeries, (ii) adjacent zone of rookeries and (iii) abandoned

rookeries. Geomorphological evolution of the coastal areas, by Holocene glacier retreat, resulted in the changing location of penguin colonies, resulting in a larger area and varying ages of phosphatization, forming ornithogenic soils with contrasting evolution degrees. Abandoned areas have greater vegetation growth, with higher diversity.