The influence of sea animals on selenium distribution in tundra soils and lake sediments in maritime Antarctica

The biogeochemical behavior of selenium (Se) has been extensively studied in Se-enriched or Se contaminated soils at low and middle latitudes. However, the Se distribution patterns have not been studied in tundra ecosystems of remote Antarctica. Here, the soils/sediments were collected from penguin and seal colonies, their adjacent tundra and lakes, tundra marsh, human-activity areas, normal tundra and the periglacial in maritime Antarctica, and total Se and seven operationally defined Se fractions were analyzed. Overall the regional distribution of Se levels showed high spatial heterogeneity (coefficient of variation, CV = 114%) in tundra soils, with the highest levels in penguin (mean 6.12 ± 2.66 μg g⁻¹) and seal (mean 2.29 ± 1.43 μg g⁻¹) colony soils, and the lowest in normal tundra soils and periglacial sediments (<0.5 μg g⁻¹). The contribution rates of penguins and seals to tundra soil Se levels amounted to 91.7% and 78.0%. The lake sediment Se levels (mean 2.15 ± 0.87 μg g⁻¹) close to penguin colonies were one order of magnitude higher than those (mean 0.49 ± 0.87 μg g⁻¹) around normal tundra. Strong positive correlations (p < 0.01) of Se concentrations between lake sediments and adjacent tundra soils, and lower Se: P (<0.001) and S: P (<1) ratios in the lake sediments close to penguin colonies, indicated the infiltration or leaching of penguin guano as the predominant Se source in lake sediment. The Se species in penguin and seal guano were dominated by SeCys₂ (76.6%) and SeMet (73.5%), respectively. The evidence from the predominant proportions of total organic matter-bound Se (Se_om, 67%–70% of total Se) in penguin or seal colony soils further supported penguin or seal guano had a great influence on the distribution patterns of Se fractions in the tundra. This study confirmed that sea animal activities transported substantial amount Se from ocean to land, and significantly altered the biogeochemical cycle of Se in maritime Antarctica.