Sources and depositional changes of aliphatic hydrocarbons recorded in sedimentary cores from Admiralty Bay, South Shetland Archipelago, Antarctica during last decades.

ABSTRACT

Organic biomarkers, as aliphatic hydrocarbons, are present in sedimentary organic matter and have been largely applied to the evaluation of recent environmental changes in the marine environment around the globe, including the Antarctic continent. Five sediment cores were taken in the Admiralty Bay, South Shetland Archipelago, Antarctica to evaluate changes in the signature of aliphatic hydrocarbons such as n-alkanes (n-C10 to n-C40) and isoprenoids as pristane and phytane, over the last decades. The total n-alkanes concentration ranged from 0.17 to 1.67 µg g-1 (mean = 0.74 ± 0.42) which is considered low and similar to pristine sediments. Aliphatic hydrocarbons present in the sedimentary pool came mostly from terrestrial sources as Antarctic lichens and mosses, and from marine sources as the macroalgae forest debris and emergent macrophytes. Anthropogenic inputs of aliphatic hydrocarbons (e.g., petroleum and their by-products) may be neglected based on the multi-proxy approach used to distinct sources of these organic compounds. In general, no significant changes in the sources of aliphatic hydrocarbons were observed along the sediment cores; however, an increased aliphatic hydrocarbons input registered between 1975 and 1992 may be related to the increase in meltwater runoff and the relatively high abundance of marine producers more adapted to increased sea temperatures.