The content and distribution of saturated hydrocarbons (n-alkanes,isoprenoid,steranes and terpanes) in the multitubular cores ANT29-M2 from the Prydz Bay of the Antarctic were analyzed using gas chromatography-mass spectrometry,and the organic matter sources,sedimentary environments and geochemical parameters of the sediments were discussed.The results showed that the carbon number of the multitubular samples ANT29-M2 was between C14 and C32 with low-carbon single peak group and main peak carbon of C18 .n-alkane gas charomatography fingerprint spectra indicated that unmixable complex compounds displayed a significant bulge,and the obvious UCM shape suggested a large input of bacteria.The ∑C21^-/∑C22^+ values varied from 1.82 to 3.9,and C21^+C22 /C28 ^+C 29 values ranged from 1.26 to 6.30,indicating that the sedimentary organic matter mainly originated from marine algae.The CPI and OEP values varied from 1.54 to 2.29 and from 4.48 to 4.82,respectively,with a significant odd even predominance.Pr/Ph values ranged from 0.34 to 0.76,significantly smaller than 1,with a clear distribution of C29 >C27 >C28 and C27 >C29 >C28 for regular steranes and a V-shaped C29 predominance and C27 predominance.This indicated that the sedimentary organic matter in the Prydz Bay originated from a mixed marine/continental source,and was deposited under a strongly reducing environment.The maturity parameters of the sedimentary strata from the Prydz Bay displayed significant inconsistency.Geochemical parameters of hopane C 32 22S/C 32 (22S+22R) and sterane C 29 αββ/(αββ+ααα) suggested a high maturity,but other geochemical parameters such as C29 ααα20S/C29 ααα(20S+20R),CPI and OEP reflected that those of columnar strata were within the range of modern marine sediments (lowly mature to immature),probably resulting from the development of microorganisms.
Yang DanZhang YichengHan XinbinZhao JunXu XuedanZhang HuijuanZhang Haisheng
The historical data of phytoplankton and chlorophyll a(Chl a)(1990–2002)obtained during the Chinese National Antarctic Research Expedition(CHINARE)in the Prydz Bay have been integrated.The results showed that the temperature,salinity,nutrients,and oxygen of seawater changed when El Nino/La Nina occurred.The variation of biological communities reflected the response of ecosystem to environmental changes.During El Ni?o period,Chl a concentration and phytoplankton community structure changed significantly,and the relative proportion of diatoms increased while dinoflagellates decreased.During La Ni?a period,the proportion of diatoms decreased,but the golden-brown algae and blue-green algae increased significantly.The variation of phytoplankton population directly affected the biodiversity of the bay,which were also quite sensitive to the marine environment changes.Meanwhile,the satellite remote sensing data of 2002–2011(December–March)have been used to study the temporal connection change of Chl a and phytoplankton in the Prydz Bay.We found that there were significant differences in the monthly variation characteristics of satellite remote sensing Chl a and sea surface temperature(SST),which had some links with sea ice melting and El Ni?o/La Ni?a events.We found that the start time of bloom advanced,lagged or synchronized with the changes of the SST,and we also found the occurrence time of phytoplankton bloom corresponded with the sea ice melting inner bay.To some extent,this study will help us understand the relationships between ENSO events and the phytoplankton bloom in the Southern Ocean.
In this study, the polycyclic aromatic hydrocarbons (PAHs) from the sediment cores M2 in the Pryza Bay of the Antarctica were quantitatively measured using GC-MS analysis, and it is found that the PAHs mainly included bicyclic naphthalene compounds, tricyclic phenanthrene and fluorine series (dibenzofuran and dibenzothiophene), and tetracyclic fluoranthene, pyrene and chrysene series. The results showed that the phenanthrene series with low molecular weight (tricyclic compounds) had a relatively higher content than the series with high molecular weight (tetracyclic compounds). The fluoranthene/(fluoranthene and pyrene) ratio of M2 varied from 0.46 to 0.54. Integrated with the content of 1,7-dimethylphenanthrene and terrigenous chrysene, it is inferred that PAHs in the sediments from the Pryzd Bay were originated from a mixed source of the products of petroleum, refined products and coal combustion, natural source and terrigenous higher plants. Complete methyl dibenzothiophene and dimethyldibenzothiophene series compounds were detected in the sediment cores, which are closely associated with a reducing environment. The ratio of dibenzothiophene to dibenzofuran was between 0.46 and 3.21, mostly greater than 0.7. Combined with the oxidation/reduction index (Pr/Ph) ranging from 0.45 to 0.61 for the sediment cores, it is indicated that these compounds were formed in a normal reducing environment. Geochemical parameters of PAHs such as TNR-1 (0.53-1.57), MPI (0.24-1.21), MDR (1.83-5.57), and MDBI (0.41-0.93), and maturity parameters such as C 29 /C 29 (+), C 31 22S/C 31 (22S+22R), C 32 22S/C 32 (22S+22R) and Ts/(Tm+Ts) were all indicative of high maturity. However, all the above parameters were significantly deviated from those of modern sediments and modern organisms, which undoubtedly shows the input of exogenous mature organic matter.
Yang DanHan XibinZhang HaishengZhang YichengXu XudanZhang Huijuan
El Nio-Southern Oscillation(ENSO)has affected penguins and their habitats in the western Antarctic Peninsula.We used both historical penguin population dynamics data(1980–2012)and sedimentary lipids in penguin droppings(1916–2001)on Ardley Island to examine the responses of the Antarctic ecosystem to ENSO(El Nin o/La Nin a)events.The results showed that during the last 30 years,climate,marine food chain changes,and human activity have significantly affected penguin population sizes on Ardley Island.The Chinstrap(Pygoscelis antarctica)and Ade′lie(P.adeliae)penguin populations showed a good correlation with ENSO events.The Chinstrap penguin population decreased significantly because it was more sensitive to increasing human disturbance(e.g.,scientific activity and tourism)than Ade′lie and Gentoo(P.papua),particularly during the breeding season.Compositional features of n-alkanes in penguin dropping sediments revealed that organic matter came from lower terrestrial plants,bacteria and algae.C23was the main nalkane heavy hydrocarbon indicating mosses and lichens in the penguin’s diet.Variation in the ratio of nC23/nC17was closely correlated with ENSO events.The bacteria intrusion index(ratio of(iC15:0?aC15:0)/nC15:0for fatty acids)reflected significant increases in microorganism activity during several periods in this area.Meanwhile,the CPIA value for fatty acids decreased because micro-organisms contributed light hydrocarbon fatty acids to penguin droppings.Our results showed that the fine structure and molecular indices of fatty acids and n-alkanes in penguin dropping sediments can be used to explain climate-driven microbial processes,and to reveal the important role that microbes and bacteria play in the relatively simple Antarctic ecosystem.
Haisheng ZhangJun ZhaoZhengbing HanBing LuHans-Ulrich Peter
The study provides one of the first lines of evidence showing linkages between Antarctic phytoplankton abundance and composition in response to ENSO, based on historical reconstruction of sediment biomarkers. In addition to sediment biomarkers, field measured and remote sensing data of phytoplankton abundance were also recorded from Prydz Bay, Eastern Antarctica. Community structure of field measured phytoplankton showed significant El Nino/La Nina-related succession during 1990 to 2002. In general, the number of algae species decreased during El Nino and La Nina years compared to normal years. Austral summer monthly variation of remotely sensed chlorophyll-a(Chl-a), particulate organic carbon(POC), and sea surface temperature(SST) indicated that ENSO impacted the timing of phytoplankton blooms during 2007 to 2011. Phytoplankton blooms(indicated by Chl-a and POC) preceded the increases in SST during El Nino years, and lagged behind the SST increases during La Nina years. Stratigraphic record of marine sedimentary lipid(brassicasterol, dinosterol and alkenones) biomarkers inferred that the proportions of different algae(diatoms, dinoflagellates and haptophytes) changed significantly between El Nino and La Nina events. The relative proportion of diatoms increased, with that of dinoflagellates being decreased during El Nino years, while it was reversed during La Nina years.
