Nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes were investigated from the algal-rich littoral zone of Lake Daming, East Antarctica during the summers of 2008/09 and 2009/10, using a static chamber technique. High N2O emissions occurred in the littoral zone with the mean flux range of 0.19–7.11 μmol N2O m-2 h-1. The mean CH4 fluxes ranged from 2.51–5.32 μmol CH4 m-2 h-1, and they were significantly affected by the lake thermal regime. There were significant differences (P < 0.05) in CH4 and N2O fluxes under the light and dark conditions, and sunlight greatly increased N2O emissions by stimulating the algal photosynthesis, but decreased CH4 emissions. Overall the littoral zone represented a weak CO2 sink with the mean flux range of -0.37–0.13 mmol CO2 m-2 h-1. The mean ecosystem respiration and photosynthesis rates varied from 0.47–2.90 mmol CO2 m-2 h-1 and from -0.33 to -2.63 mmol CO2 m-2 h-1. The combined global warming potential (GWP) of N2O and CH4 fluxes completely counteracted and surpassed CO2 uptake by the algal photosynthesis, and high GWP-positive of N2O and CH4 emissions might convert an algal-rich lake site with a net CO2 uptake into a net radiative forcing source during the ice-free period.

Very little attention has been paid to quantifying ammonia (NH3) emissions from Antarctic marine animal excreta. In this paper, penguin guano and ornithogenic soils from four penguin colonies and seal colony soils were collected in coastal Antarctica, and laboratory experiments were conducted to investigate potential NH3 emissions and effects of environmental factors on NH3 fluxes. Ammonia fluxes were extremely low from the frozen samples. Significantly enhanced NH3 emissions were observed following thawing. The mean fluxes were 7.66 ± 4.33 mg NH3 kg-1 h-1 from emperor penguin guano, 1.31 ± 0.64 mg NH3 kg-1 h-1 from Adélie penguin guano and 0.33 ± 0.39 mg NH3 kg-1 h-1 from seal colony soils during the thawing period. Ammonia emissions from penguin guano were higher than those from ornithogenic soils during freezing-thawing cycles (FTCs). The temperature, pH, total nitrogen (TN) and drying-wetting conversion had an important effect on NH3 fluxes. For the first time, we provide a quantitative relationship between NH3 flux and temperature, TN and pH. Our results show that marine animal excreta and ornithogenic soils are significant NH3 emission sources. In coastal Antarctica, FTC-induced NH3 emissions might account for a large proportion of annual flux from marine animal colonies due to high freezing-thawing frequency.

We investigated nutrient composition and the potential for greenhouse gas production in Antarctic penguin guano, ornithogenic soils and seal colony soils through a laboratory incubation experiment. Total organic carbon contents ranged from 0.2–14.7% and total nitrogen contents ranged from 0.05–3.60% across all the samples. Penguin guano and the soils had the δ13Corg values of -28.4‰ to -22.8‰ and highly enriched δ15N values (8.28–35.51‰), indicating a rapid N cycling in local ecosystems. The mean CO2 and CH4 emission rates from penguin guano were significantly higher than those from the soils under aerobic or anaerobic conditions. The CO2-C/TOC rate indicated that the bioavailability of TOC was markedly higher in penguin guano than in the soils. These soils showed higher N2O emission rates under anaerobic conditions, indicating that denitrification may be the major process in N2O emission. The CO2 and CH4 emissions have a significant correlation with TOC in both penguin guano and the soils. Our results show that marine animal excreta are an important factor determining storage and composition of nutrients in coastal Antarctica, and that they may considerably affect current and future net fluxes of greenhouse gases in this region.

In order to reconstruct past changes in penguin populations we performed geochemical analyses on a penguin ornithogenic sediment core DG4 retrieved from a lake catchment on Gardner Island, Vestfold Hills. P, Se, F, S, As, Sr and Cu in DG4 were identified as the bio-element assemblage by R-clustering analyses on the elemental concentrations and comparisons with those in bedrock and fresh penguin guano. Factor analysis on the levels of these bio-elements in the core permitted a reconstruction of variations in historical penguin populations at Gardner Island spanning the past 8500 years. The penguin population showed significant fluctuations, reaching its highest density between 4700–2400 calibrated years before present. This coincides with evidence for a late Holocene warm period in the Vestfold Hills, similar to that associated with the late Holocene penguin optimum recorded in the Ross Sea and Antarctic Peninsula regions.

During CHINARE-22 (December 2005–March 2006), we investigated six penguin colonies in the Vestfold Hills, East Antarctica, and collected several penguin ornithogenic sediment cores, samples of fresh guano and modern penguin bone and feather. We selected seven penguin bones and feathers and six sediments from the longest sediment core and performed AMS14C dating. The results indicate that penguins occupied the Vestfold Hills as early as 8500 calibrated years before present (cal. yr bp), following local deglaciation and the formation of the ice free area. This is the first report on the Holocene history of penguins in the Vestfold Hills. As in other areas of Antarctica, penguins occupied this area as soon as local ice retreated and the ice free area formed, and they are very sensitive to climatic and environmental changes. This work provides the foundation for understanding the history of penguins occupation in Vestfold Hills, East Antarctica.

Gentoo penguin Pygoscelis papua is an important component of the Antarctic marine ecosystem. In this paper, we use an indirect approach, a geochemical method combining with 137Cs and 210Pb CRS mode dating, to study the dynamics of the gentoo population and colony on Barton Peninsula, King George Island, in the maritime Antarctic. Five sediment profiles were sampled in the zone between the gentoo penguin colony and tundra vegetation on this peninsula and the sediment sequence and typical elements from penguin guano were analysed. Results showed that the levels for typical elements display a dramatic change at around 5 cm depth, indicating the strong impact of penguin guano. The sediments below 5 cm showed lower concentrations in these elements, suggesting that these sediments had received little impact from penguin guano. By Q-mode factor analysis, a method for decomposing multiple factors, we found that over the past sixty years the gentoo colony showed a rapid enlargement and the tundra vegetation had been destroyed. Possible factors responsible for the enlargement of the penguin colony are tentatively discussed.