Renbin Zhu

Penguin population dynamics for the past 8500 years at Gardner Island, Vestfold Hills

Abstract 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.

Potential ammonia emissions from penguin guano, ornithogenic soils and seal colony soils in coastal Antarctica: effects of freezing-thawing cycles and selected environmental variables

Abstract 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.

Geochemical evidence for rapid enlargement of a gentoo penguin colony on Barton Peninsula in the maritime Antarctic

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.

Nutrient compositions and potential greenhouse gas production in penguin guano, ornithogenic soils and seal colony soils in coastal Antarctica

Abstract 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.

Stable isotope natural abundance of nitrous oxide emitted from Antarctic tundra soils: effects of sea animal excrement depositions.

Nitrous oxide (N2O), a greenhouse gas, is mainly emitted from soils during the nitrification and denitrification processes. N2O stable isotope investigations can help to characterize the N2O sources and N2O production mechanisms. N2O isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of N2O emitted from Antarctic tundra ecosystems have been reported although the coastal ice-free tundra around Antarctic continent is the largest sea animal colony on the global scale. Here, we report for the first time stable isotope composition of N2O emitted from Antarctic sea animal colonies (including penguin, seal and skua colonies) and normal tundra soils using in situ field observations and laboratory incubations, and we have analyzed the effects of sea animal excrement depositions on stable isotope natural abundance of N2O. For all the field sites, the soil-emitted N2O was 15N- and 18O-depleted compared with N2O in local ambient air. The mean delta values of the soil-emitted N2O were delta15N = -13.5 +/- 3.2 per thousand and delta18O = 26.2 +/- 1.4 per thousand for the penguin colony, delta15N = -11.5 +/- 5.1 per thousand and delta18O = 26.4 +/- 3.5 per thousand for the skua colony and delta15N = -18.9 +/- 0.7 per thousand and delta18O = 28.8 +/- 1.3 per thousand for the seal colony. In the soil incubations, the isotopic composition of N2O was measured under N2 and under ambient air conditions. The soils incubated under the ambient air emitted very little N2O (2.93 microg N2O--N kg(-1)). Under N2 conditions, much more N2O was formed (9.74 microg N2O--N kg(-1)), and the mean delta15N and delta18O values of N2O were -19.1 +/- 8.0 per thousand and 21.3 +/- 4.3 per thousand, respectively, from penguin colony soils, and -17.0 +/- 4.2 per thousand and 20.6 +/- 3.5 per thousand, respectively, from seal colony soils. The data from in situ field observations and laboratory experiments point to denitrification as the predominant N2O source from Antarctic sea animal colonies.

Penguin occupation in the Vestfold Hills

Abstract 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.

Paleoecological implications of the nitrogen isotope signatures in the sediments amended by Antarctic seal excrements

Abstract The nitrogen isotope signatures in the sediments amended by seal excrements, from Fildes Peninsula of King George Islands, Antarctica, were examined for their paleoecological application potential. The contents of total organic carbon (TOC) and total nitrogen (TN) and the atomic C/N ratios in the sediments show that the organic carbon and nitrogen are predominantly of marine origin and derived from seal excrements. The remarkably high δ15N values in the sediments may be related to at least two important factors of trophic enrichment and NH3 volatilization, which requires further studies. The large variations in the seal hair abundances and the determined δ15N values in the sediments signify similar changes of the historical seal populations around the study site. A significant negative correlation between the δ15N values and seal hair abundance was observed, and this suggests that the δ15N values, like the number of seal hairs, can be used as a paleoecological proxy for the historical seal popula...

Occurrence of matrix-bound phosphine in polar ornithogenic tundra ecosystems: Effects of alkaline phosphatase activity and environmental variables

Phosphine (PH(3)), a reduced phosphorus compound, is a highly toxic and reactive atmospheric trace gas. In this study, a total of ten ornithogenic soil/sediment profiles were collected from tundra ecosystems of east Antarctica and Arctic, and matrix-bound phosphine (MBP), the phosphorus fractions and alkaline phosphatase activity (APA) were analyzed. High MBP concentrations were found in these profiles with the range from 39.59 ng kg(-1) dw to 11.77 μg kg(-1) dw. MBP showed a consistent vertical distribution pattern in almost all the soil profiles, and its concentrations increased at soil surface layers and then decreased with depths. MBP levels in the ornithogenic soils were two to three orders of magnitude lower than those in ornithogenic sediments. The yield of PH(3) as a fraction of total P in all the profiles ranged from 10(-5) to 10(-9) mgPH(3) mg(-1)P with higher mean PH(3) yield in the ornithogenic sediments. The ornithogenic soils showed high concentrations of total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (IP) and metal elements (Cu, Zn, Mn, Fe, Al and Ca) but low MBP levels, vice versa for the ornithogenic sediments. No correlation had been obtained between MBP concentrations and IP, OP and TP. There existed an exponential correlation (r=0.67, p<0.01) between MBP and soil/sediment moisture. MBP concentrations showed a significant positive correlation with APA (r=0.668, p<0.0001), total organic carbon (r=0.501, p<0.0001), total hydrogen (r=0.483, p<0.0001) and total sulfur (r=0.398, p<0.001), indicating that the production of MBP is associated with microbially mediated factors rather than the contents of TP, IP and OP in the P-enriched ornithogenic soils/sediments. Our results indicated that MBP is an important gaseous link in the phosphorus biogeochemical cycles of ornithogenic tundra ecosystems in Antarctica and Arctic.

Stimulation of gaseous phosphine production from Antarctic seabird guanos and ornithogenic soils

Matrix-bound phosphine (MBP) is a general term used to indicate non-gaseous reduced phosphorus compounds that are transformed into phosphine gas upon reaction with bases or acids. Antarctic seabird guanos and ornithogenic soils were used as materials to compare the different digestion methods for transforming matrix-bound phosphine into phosphine gas. The results demonstrated that more phosphine gas in most of Antarctic environmental materials was formed of matrix-bound phosphine by caustic digestion than by acidic digestion. The comparative study on different digestion methods also revealed that the fraction of MBP converted to gaseous phosphine during the digestion depended on the temperature. The optimal digestion temperature was close to 70 degrees C and the optimal digestion time was about 20 min. Acidic conditions were more favorable for the release of matrix-bound phosphine compared to the neutral conditions. A proper water dilution can increase the production and emission of phosphine from the Antarctic penguin guanos.

Summertime fluxes of N2O, CH4 and CO2 from the littoral zone of Lake Daming, East Antarctica: effects of environmental conditions

Abstract 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.