Genesis, mineralogy and ecological significance of ornithogenic soils from a semi-desert polar landscape at Hope Bay, Antarctic Peninsula

Large amounts of organic matter of marine origin are seasonally deposited on ice-free soils by birds and mammals, especially penguins, in some restricted Antarctic terrestrial ecosystems. The incorporation of this material into the mineral soil matrix becomes the main pathway for the widespread formation of phosphate minerals and ornithogenic soils, enhancing local biodiversity and complexity. These soils have been well-studied in Maritime Antarctica, and comparatively neglected in the cold, dry polar Antarctica. Hence, we studied the influence of penguins on soil and landscape formation at Hope Bay, a transition climatic zone in Antarctic Peninsula, where no previous pedological study has been undertaken with regards to soil phosphatization. Ten pedons, nine of which are ornithogenic, were described, sampled, and analyzed for physical, chemical and mineralogical properties. Results indicate that the slow mineralization of bird guano, coupled with high levels of organic matter and reduced leaching, notably Ca, contribute to reduced soil acidification and low exchangeable Al3+ content, unlike ornithogenic soils from Maritime Antarctica. Phosphate minerals typical of the phosphatization process, such as taranakite, minyulite, leucophosphite, struvite, and fluorapatite, were detected. In Hope Bay, they are subjected to very slow rates of dissolution, neoformation of secondary phosphatic minerals, and mineralogical transformation and leaching processes. Ornithogenesis is viewed as a mechanism of sea-land nutrient transfer, enriching the latter, since the parent rocks are chemically poor sedimentary materials. On the other hand, the presence of kaolinite indicates wetter climate conditions in the past, with periods with greater moisture and weathering, compared with the current semi-polar desert environment. We conclude that the phosphatization process overprints previously weathered sedimentary materials. (C) 2013 Elsevier B.V. All rights reserved.