Seabirds enrich Antarctic soil with trace metals in organic fractions.

Coastal areas of Antarctica are subjected to anthropic contamination from around the world by trace metals biotransported and accumulated by seabird excrements. To explore this hypothesis, this study investigated the influence of seabirds on the contents of trace metals in soil organic fractions from Antarctica under different climatic conditions and from different parent materials. For this, soil profiles from the Maritime Antarctica region were selected based on the criteria of ornithogenesis, parent material, and climate. The contents of C, N, and selected metals (Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn) were analysed in the organic matter associated with minerals (MAOM), the particulate fraction (POM), and in the total soil (MAOM + POM). The ornithogenic soils presented the highest amounts of C and N in the soil, MAOM, and POM as compared to nonornithogenic soils. Seabird activity resulted in an enrichment of Pb, Zn, and Cu. Among these biotransported metals, Cu and Zn seem to originate from natural biogenic processes in marine food chains, unlike Pb, which seems to come from anthropogenic sources. The soils developed from igneous rocks presented higher amounts of Ba, Co, Cu, Fe, Mn, and Sr in the soil, MAOM, and POM than soils from sedimentary rocks. The climate had no clear effect on most metals. Hence, seabirds enrich soils, MAOM, and POM with Cu, Zn, and Pb, whereas the amounts of Ba, Co, Cr, Fe, Mn, Ni, and Sr are mainly lithogenic, associated with the parent material. Monitoring biotransported trace metals in ornithogenic soils is of great importance, since they can create environmental toxicity to terrestrial plants and animals and can influence the food chain in the coastal areas of Antarctica.