A preliminary record of the historical seabird population in the Larsemann Hills, East Antarctica, from geochemical analyses of Mochou Lake sediments

Abstract

2007 (April): A preliminary record of the historical seabird population in the Larsemann Hills, East Antarctica, from geochemical analyses of Mochou Lake sediments. Boreas, Vol. 36, pp. 182 Á197. Oslo. ISSN 0300-9483.An 85-cm long sediment sequence from Mochou Lake on Mirror Peninsula in the Larsemann Hills, East Antarctica, was investigated for elemental geochemistry, biogeochemistry and strontium (Sr) isotopic composition in the acid-insoluble and acid-soluble fractions. The biogeochemical data showed that the freshwater lacustrine sediment originated after 2750 BP. The element Zn, Cu, F, P and Se fluxes displayed almost the same vertical distribution patterns, and their ratios over loss on ignition had strong positive correlations with each other, indicating a common source, probably from seabird droppings. The Sr isotopic compositions provided further evidence of the influence of seabirds on the freshwater lacustrine sediments. The 87 Sr/ 86 Sr ratios determined in the acid-soluble fraction were remarkably lower than those of the acid-insoluble fraction; with a bedrock 87 Sr/ 86 Sr signature, they were close to those of the marine-derived Sr and were negatively correlated with total amino acids. Using the ratio vs. depth profiles of P, Zn, Cu, Se, F, As, Cd and Ni fluxes over Al, we reconstructed the historical seabird population in the catchment area of Mochou Lake. During the past c. 2800 years, the seabird population has experienced substantial changes in the absence of human activity, and four troughs were identified. After comparison with the palaeoclimatic records and glacial advance and retreat history, the pronounced seabird population declines seem to be related to climatic deterioration.

Last Millennium Adélie Penguin Mortality and Colony Abandonment Events on Long Peninsula, East Antarctica

“…A 4,836‐year geochemical record from a sediment core from 3‐m water depth in Mochou Lake (69°22′S, 76°22′E), in the Larsemann Hills, 120 km from the Vestfold Hills, was obtained by Liu et al (). Based on sediment lithology and other published data, Mochou Lake was elevated above sea level from 2750 years BP (Liu et al, ; Verleyen et al, ).…”

“…A 4,836‐year geochemical record from a sediment core from 3‐m water depth in Mochou Lake (69°22′S, 76°22′E), in the Larsemann Hills, 120 km from the Vestfold Hills, was obtained by Liu et al (). Based on sediment lithology and other published data, Mochou Lake was elevated above sea level from 2750 years BP (Liu et al, ; Verleyen et al, ). Within the sediment core, elements indicative of terrestrial weathering, Aluminum (Al) and Silicon (Si) exhibit distinct peaks at 750–550 years BP, while salinity and biological proxies, Boron (B), Strontium‐to‐Barium ratio (Sr/Ba), LOI 550 , and amino acid content exhibit minima (Figure S2).…”

“…Loss on ignition at 550 °C (LOI 550 ) represents the ratio of the organic matter to the total dry weight of a subsample, since the organic matter decomposes into gaseous CO 2 at this temperature. LOI 550 of sediments is indicative of the biological activity in the surrounding areas (Liu et al, ; Zhou et al, ). LOI 550 was measured using the thermogravimetry method.…”

Dissolved major ions, Sr and 87 Sr/ 86 Sr of coastal lakes from Larsemann hills, East Antarctica: Solute sources and chemical weathering in a polar environment

“…Seabirds and penguins excreta have also been invoked as a possible source to the chemistry of Antarctic lake water (Spurr, ). Further, the significance of this source in regulating the sedimentary Sr isotopic data was established by Liu et al () through investigation of 87 Sr/ 86 Sr data for lacustrine sediments and seabird excreta. These excreta are often enriched in P, C and N and may supply about 2.5 wt% of the animal body part per day (Scherer, Gibbons, Stoops, & Muller, ).…”

“…More than 150 freshwater lakes, ranging from small to deep glacial water bodies, are present in the Larsemann Hills (Liu et al, ). These lakes, owing to low nutrient availability and biological productivity, are generally oligotrophic in nature (Sabbe et al, ).…”