| Summary: | The soils and hydrology of Seabee Hook, Cape Hallett, Antarctica were investigated during the 2003-04 and 2004-05 summer periods. Seabee Hook is a low lying spit that has been built up by the deposition of material, from nearby cliffs, by strong tidal currents. Seabee Hook is also the location of a large Adelie penguin (Pygoscelis adeliae) colony and was the location of a USNNZ research base, occupied from 1957-73. A soil map is presented of the Seabee Hook area. A soil association was identified between penguin mounds and intermound areas. Penguins build nests of stones on elevated sites, which at Cape Hallett are relict beach ridges. The penguins have exaggerated the topography of the beach ridges, primarily by adding 3-10 cm size stones ("penguin-stones") and guano, to form penguin mounds. Soils on penguin mounds contain guano in the upper 50 cm of the gravelly and sandy profile, and the guano layer overlies sub-rounded beachdeposited gravel and sand. Soils between beach ridges contain a thin veneer ( <3cm) of guano overlying the same basaltic gravelly sand found in the lower parts of the mound soils. The soils formed on the mounds have been classified usingUSDA Soil Taxonomy as Typic Haplorthels, and the soils formed between mounds have been classified as Typic Haplorthels/Typic Aquorthels depending on their soil moisture contents. The soil of the penguin mounds was enriched in many elements including nitrogen, organic carbon, phosphorus, cadmium, zinc, copper and it had increased electrical conductivity in soil horizons influenced by penguin guano compared to guano free horizons, soils from intermound areas, and soils away from the penguin colony. Radiocarbon dates from five penguin bones buried at the bottom of soil profiles indicate that Seabee Hook has been colonized by penguins for at least1000 years. That the colonization of Seabee Hook may have been rapid is evidenced by the consistent thickness of "penguin stones" and guano on top of the beach ridges throughout the area. Groundwater was situated perched above the ice cement as a shallow (<1-30 cm thickness of groundwater) unconfined aquifer. Groundwater within the penguin colony was sourced from melting snow drifts and ground ice. The occurrence of groundwater within the penguin colony at Seabee Hook showed considerable spatial and temporal variations over the 2003-04 and 2004-05summers, with ice cement levels decreasing from November and groundwater beginning to accumulate in early-December. Groundwater velocity through the permeable gravel and sand (porosity 23-33%) was up to 7.8 m day⁻¹, with hydraulic conductivities of 5 x 10⁻⁴ m s⁻¹ to 5 x 10⁻⁹ m s⁻¹. Groundwater abundance varied on an annual basis depending on the amount of snowmelt occurring during summer. The 2003-04 summer had a higher water table within the penguin colony than the 2004-05 summer. During 2003-04, surface water commonly occurred as ephemeral and intermittent streams and ponds. During2004-05, water was mostly confined to groundwater within the penguin colony, where it occurred in topographic lows. Surface water was present in only a few ponds within the colony during 2004-05, and was more common in the high meltwater zones away from the penguin colony. The penguins and close proximity to the ocean have affected the groundwater chemistry, with groundwater in the penguin colony elevated in salt (14 times more sodium, 41 times more potassium), nitrogen (7 times more nitrate,416 times more ammonia), and phosphorus (33 time more total phosphorus)compared to groundwater sourced away from the penguin colony on Seabee Hookand also compared to other terrestrial waters in Antarctica.
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