Occurrence and sources of pollutants in the soils of penguin colonies in the South Shetland Islands, North-West coast of the Antarctic Peninsula

Seabirds are considered to be biological pumps that transfer large quantities of nutrients and pollutants from the marine environment to land. This study assessed the concentrations and sources of potentially toxic trace metals and polycyclic aromatic hydrocarbons (PAHs) in penguin colonies on the South Shetland Islands. Soil samples and penguin droppings were collected from four sites on Livingston and Deception Islands. The soils were characterised by low organic carbon content, sandy texture, neutral to acidic pH and low electrical conductivity. Significant enrichment of nutrients, trace metals (e.g., P, Zn, Cu) and PAHs was observed in colony soils relative to control areas (no penguins), suggesting that penguin droppings are the main source of trace metals. PAHs had different sources: volcanic activity, biological deposition and minor human influence. Elevated levels of PAHs on Deception Island were associated with penguin droppings and past volcanic eruptions. Concentrations of PAHs do not exceed toxicity thresholds for marine organisms, while Cu and Zn contents at some locations sites exceed critical levels, suggesting potential toxicity risks at local sites, especially if these metals are leached into shallow water bodies. Ultimately, the findings establish that penguin colonies act as significant drivers in modulating the biogeochemical cycles of nutrients and contaminants within Antarctic coastal systems.