The distribution of phytoplankton size and major influencing factors in the surface waters near the northern end of the Antarctic Peninsula

The waters near the Antarctic Peninsula have always been a study hot spot because of their variable and unique oceanographic conditions.To determine the distribution and possible influencing factors on phytoplankton size and abundance near the Antarctic Peninsula,a large-scale survey was conducted during the austral summer of2018.Samples were collected in 27 stations located in the Drake Passage(DP),South Shetland Islands(SSI),and South Orkney Islands(SOI).Phytoplankton communities were described using chlorophyll a(Chl a),flow cytometry and light microscopy to cover a size range from pico-to microphytoplankton.Nanophytoplankton,especially small nanophytoplankton(2-6μm)with abundance ranging from 0.66×10^(3) cells/mL to 8.46×10^(3) cells/mL,was predominant throughout the study area.Among different regions,there was an obvious size shift.The proportion of picophytoplankton near the Elephant Island(EI)and DP was higher than other regions,and larger cells were found mainly in east of SOI.The distribution of phytoplankton abundance detected by flow cytometry was not completely consistent with Chl a concentrations due to the contribution of larger cells to Chl a.Possible influencing factors on the phytoplankton size distribution were discussed.The properties of water masses such as temperature and salinity can influence the phytoplankton size distribution.Correlation analysis revealed that only picophytoplankton is significantly correlated with salinity.Light and Fe availability might affect phytoplankton abundance and size distribution especially near the waters of SSI and EI in this study.It was also speculated that the abundance of cryptophytes is possibly related to ice melting.

Inferring trophic variation for Antarctic krill(Euphausia superba) in the Antarctic Peninsula from the austral fall to early winter using stable isotope analysis

The Antarctic krill（Euphausia superba） is a key species in the Southern Ocean ecosystem and an important link in the food web of the Antarctic ecosystem. The trophic information for this species during the transition from the austral fall to the winter is important to understand its poorly known overwintering mechanisms. However, the few studies on the topic differ in their results, in terms of both spatial and temporal variables. We investigated the size dependence and monthly and regional variation in δ^（13） C and δ^（15） N values of adult krill in the Antarctic Peninsula, in the austral fall（April to May） and the early winter（June）. We aimed to examine the trophic variations of krill occurred during this period, and the relationship between krill and their feeding environment in the Antarctic marine ecosystem. The following results were obtained：（1） no significant relationship was observed between size and the δ13 C value of krill, but the δ15 N value of krill presented a remarkable association with size;（2）the δ13 C values of krill increased during the austral fall, but no remarkable variation existed at the onset of winter,and the δ15 N values were not significant different during this period;（3） mean δ15 N values of krill differed significantly between the Bransfield Strait and the South Shetland Islands. Our data imply that adult krill present size-, season-, and region-dependent trophic variation during the transition from austral fall to early winter in the Antarctic Peninsula.

Environmental drivers of phytoplankton crops and taxonomic composition in northeastern Antarctic Peninsula adjacent sea area

The ecosystem of the sea region adjacent to the Antarctic Peninsula is undergoing remarkable physical and biological changes, in the context of global warming. However, understanding of the dynamics of phytoplankton taxonomic composition in this marginal ice zone remains unclear. In this study, seawater samples collected from 36 stations in the northeastern Antarctic Peninsula were analyzed for nutrients and phytoplankton pigments.Combining with CHEMTAX analysis, remote sensing data, and physicochemical measurements, we investigated the relationships between phytoplankton crops, taxonomic composition, and marine environmental drivers.Integrated chlorophyll a(Chl a) concentrations(200 m) varied from 8.9 mg/m^(2)to 64.2 mg/m^(2), with an average of(23.2±12.0) mg/m^(2)and higher phytoplankton biomass concentrated in the coastal region of South Orkney Island and South Shetland Island. Diatoms were the dominant functional group(63%±21%). Higher proportions of diatoms were associated with higher Chl a(r=0.40, p<0.01), stable water columns(r=0.20, p<0.01), higher Si/P ratios(r=0.34, p<0.01), higher photosynthetically active radiation intensity(r=0.64, p<0.01), and higher sea ice melt water contributions(MWC, r=0.20, p<0.01). Conversely, Phaeocystis antarctica contributed a smaller overall proportion(31%±18%) and was more concentrated in the offshore water masses(e.g., Philip Ridge and South Scotia Ridge) with lower light levels(r=-0.58, p<0.01), deeper mixed layer depths(r=0.17, p<0.05), higher nutrient concentrations(e.g., N, P, and Si, r>0.35, p<0.01), and lower MWC(r=-0.20, p<0.01). In comparison, the total contribution from green flagellates(4%±5%), cryptophyta(1%±3%), dinoflagellates(1%±4%), and cyanobacteria(1% ± 5%) was only 6%. In offshore regions with well-mixed water, less varied taxonomic composition and lower crops with a higher proportion of nanophytoplankton were observed. In contrast, significantly decreasing crops below the mixed layer depth was observed in water columns with strong stratification, where the dominant phytoplankter changed from diatoms to P. antarctica. These findings have important implications for better understanding the future dynamics of marine ecosystems in the sea area adjacent to the Antarctic Peninsula.

A new look at the first dinosaur discovered in Antarctica:reappraisal of Antarctopelta oliveroi(Ankylosauria:Parankylosauria)

The first dinosaur discovered in the Antarctic continent was the ankylosaur Antarctopelta oliveroi in the 1980s.Nevertheless,since then several hypotheses of phylogenetical relationships have been proposed because these have been depended on how the skeletal remains have been interpreted.The main obstacle for clarifying its phylogenetic position is that many portions of the skeleton remain unknown,in addition to the presence of unknown characters in typical ankylosaurs.Considered an ankylosaurid,nodosaurid,or even a chimaera,a recent proposal based on mostly complete material of a new ankylosaur from Chilean Patagonia provided support for a novel phylogenetic hypothesis:Antarctopelta and other southern ankylosaurs are an early branching clade,the Parankylosauria,whose origin probably dates to the Late Jurassic.In the light of this new view,a redescription of the available skeletal remains is provided together with a new reconstruction of the first Antarctic dinosaur known to the science community.

Review of the Cretaceous avian diversity of Antarctica:a changing scenario for the evolution of early Neornithine birds

The worldwide record of Cretaceous Neornithes and Neornithine-like birds is both controversial and poorly understood.However,in recent years,the Antarctic continent has yielded a substantial number of Maastrichtian avian specimens,contributing significantly to our understanding of the early evolution of this group.Simultaneously,the keen interest and collaborative efforts of various paleornithologists have resulted in a wealth of knowledge,which we have thoroughly reviewed,updated,and discussed in the context of recent discoveries.

Distributions of surface sediments surrounding the Antarctic Peninsula and its environmental significance

We analyzed grain size composition to provide information on the types and distributions as well as depositional varieties of marine surface sediments from the area surrounding the Antarctic Peninsula. The samples retrieved from the study area contain gravel, sand, silt and clay. As suggested by bathymetry and morphology, the study area is characterized by neritic, hemipelagic and pelagic deposits. The glacial-marine sediments can be divided into two types, residual paratill and compound paratill, which are primarily transported by glaciers and as ice-rafted debris. Ocean current effects on deposition are more obvious, and the deposit types are distributed consistently with terrain variations.

The sea/land breeze in the northern coastal area of Shandong Peninsula

In this paper the seasonal variation and structural characteristics of the sea/ land breeze in the northern coastal area of' Shandong Peninsula are studied in two ways: one is the analysis of the observed wind data, and the other is numerical simulation and experiments. Firstly, the hour to hour wind data through the year 1984 at Longkou Meteorological Station and Yantai Oceanographic Station are analysed through energy spectra and hodograph. It is revealed from the analysed results that the effects of the sea/ land breeze in the area are notable in spring, summer and fall, especially in May. However, in winter the effects of sea / land breeze are not obvious. because the cold noitherly is prevailing. Secondly, a two-dimensional non- linear model of primitive equations is used to study the sea / land breeze circulation in May in the area. The results of numerical simulation consist basically with the analysed results of the observed sea / land breeze. A reasonable theoretical structure of the sea / land breeze circulation is displayed, and a new undeerslanding of the developmental mechanism of land breeze circulation in that area is obtained. Lastly, numerical experiments about the effects of large scale wind and temperature fields upon the sea / land breeze circulation are performed.

Biomarker records of D5-6 columns in the eastern Antarctic Peninsula waters:responses of planktonic communities and bio-pump structures to sea ice global warming in the past centenary

Molecular biomarkers(e.g.,isoprenoid glycerol dialkyl glycerol tetraethers(iGDGTs)and proxies,such as di-unsaturated to tri-unsaturated highly branched isoprenoids(D/T)ratio,total organic carbon,δ^(13)C and ice-rafted debris(IRD))were used to reconstruct the dominant phytoplankton(diatoms,dinoflagellates and coccolithophores),phytoplankton and zooplankton productivity,biological pump structure,and archaea assemblage(Euryarchaeota and Crenarchaeota)from a marine sediment core(D5-6)dated with^(210)Pb(1922–2012).We characterized the environmental response to sea ice variations/global warming off the eastern Antarctic Peninsula.The results showed that(1)the biomarkers brassicasterol(average=519.79 ng·g^(-1)),dinosterol(average=129.68 ng·g^(-1))and C37 alkenones(average=40.53 ng·g^(-1))reconstructed phytoplankton(average=690.00 ng·g^(-1))and zooplankton(cholesterol average=669.25 ng·g^(-1))productivity.The relative contribution to productivity by different phytoplankton groups was diatoms>dinoflagellates>coccolithophores.This is consistent with field surveys showing that diatoms dominate the phytoplankton in waters adjacent to the Antarctic Peninsula.(2)The relative abundances of different highly branched isoprenoids reflected the contributions of sea ice algae and open water phytoplankton(D/T=1.2–30.15).Phytoplankton productivity and sea ice showed a good linear relationship with a negative correlation,indicating that more open water during periods of warming and reduced sea ice cover led to an enhanced biological pump.(3)Over the past 100 years,phytoplankton productivity and zooplankton biomass increased.This trend was particularly evident in the last 50 years,corresponding to increased global warming,and showed a negative correlation with IRD and D/T.This suggests that with decreasing sea ice coverage in a warming climate,diatom biomass greatly increased.Coccolithophore/diatom values and the ratio of C37 alkenones to total phytoplankton productivity decreased,indicating the proportion of coccolithophores in the phytoplankton community decreased.The reduction in coccolithophores changes the phytoplankton assemblage and affects the overall efficiency of the biological pump and carbon storage.(4)The results also showed that the abundance of iGDGTs and archaea phyla(Euryarchaeota and Crenarchaeota)showed consistent changes over the past 100 years in response to global warming.Since 1972,trends in archaea,phytoplankton and zooplankton showed variations but a consistent decline.Whether their response to the changing climate off the Antarctic Peninsula involves interactions and influence among different marine biological groups remains an open question.As a result of global warming and reductions in Antarctic sea ice,the relative effectiveness of the Antarctic biological pump can significantly affect global ocean carbon storage.

A case study on fine weather in Western Antarctic Peninsula

Based on observational data and facsimile charts from Dec. 1994 to Nov. 1995 of Chinese Antarctic Great Wall Station, the local fine weather was studied. Pressure, temperature and humidity field, and aerological stratification were analyzed synoptically. Two kinds of fine weather with different physical characteristics were found; one was caused by the spreading of subtropical high with high tem- perature and high humidity, and another was connected with polar high with low temperature and low humidity. The research provide a synoptic background for the local fine weather forecast.

MINERALOGICAL CHARACTERISTICS AND CONTROL FACTORS OF SURFACE SEDIMENTS IN THE SEA AREA NORTHWEST OF THE ANTARCTIC PENINSULA

Analysis and study of clastic and clay minerals of surface sediments and their chemical composition in the sea area northwest of the Antarctic Peninsula enable the authors to divide this area basically into four mineralogical provinces : (1) the mineral ogical province of coast and island shelf of the Southern Shetland Islands, (2) the mineral ogical province of the eastern Bransfield Strait, (3) the mineral ogical province of the western Bransfield Strait, and (4) the mineral ogical province of the western Antarctic Peninsula. Finally, the relationships between the mineral distribution and geologic ,structure, material sources, glaciers, currents, and environments are briefly described.

MATHEMATICAL STATISTICS OF HEAVY MINERALS AND THEIR REE AND TRACE ELEMENTS IN THE NORTHWESTERN SEA AREA OF ANTARCTIC PENINSULA

Based on the analysis and mathematical statistics of quantitative data on both the heavy minerals and their REE (La, Ce, Nd, Sm, Eu, Tb, Yb, Lu), trace (Zr, Hf, Th, Ta, U, Rb, Sr, Zn, Co, Ni, Cr, As, Sc) and major (Fe) elements in the surface sediments in the northwestern sea area of Antarctic Peninsula, the authors find that the heavy minerals as the carriers of REE and trace elements should not be overlooked.Q-mode factor analysis of the heavy minerals provides a 3-factor model of the heavy mineral assemblages in the study area, which is mainly controlled by the origin of materials and sea currents. The common factor P1, composed mainly of pyroxene and metal minerals, and common factor P2, composed of hornblende, epidote and accessory minerals, represent two heavy mineral assemblages which are different from each other in both lithological characters and origin of materials. And common factor P3 probably results from mixing of two end members of the above-mentioned assemblages. R-mode group analysis of the heavy minerals indicates that there are two heavy mineral groups in the sea area, which are different from each other in both genesis and origin of materials. With the help of R-mode analysis, 22 elements are divided into 3 groups and 9 subgroups. These element assemblages show that they are genetically related and that they are different in geochemical behaviors during diagenesis and mineral-forming process. In addition, the relationship between the heavy mineral assemblages and the element subgroups is also discussed.

Variations and relations between chlorophyll concentrations and physical-ecological processes near the West Antarctic Peninsula

The West Antarctic Peninsula(WAP)region is one of the most productive marine ecosystems in the Southern Ocean that support the food web for phytoplankton,krill spawning or recruitment and several krill consumers at higher-trophic level like penguins and Antarctic fur seals.Characterized by channels and islands,the complex topography of the WAP generates interconnected circulation patterns,strongly influencing vertical stratification,nutrient availability and distribution of marine organisms.Additionally,rapid climate change associated with major climate modes like the Southern Annular Mode(SAM)and El Niño-Southern Oscillation(ENSO)has significant effects on long-term variations of physical environments and biological production.The objective of this study is to reveal the spatial-temporal variations of phytoplankton biomass in the WAP region and the modulating physical-ecological processes.By using 9-year hydrographic and ecological data of five transects collected by the Palmer Long-Term Ecosystem Research,the horizontal and vertical distributions of several physical and ecological properties,with a particular focus on chlorophyll(Chl)concentration were explored.Regression analysis among area-averaged properties and properties at single stations was performed to reveal the relationship between the interannual variations of physical and ecological processes.The correlation results showed that Chl concentration exhibited a positive relationship with both the circumpolar deep water(CDW)intrusion and vertical stratification,but showed a negative correlation with SAM at some specific stations.However,certain processes or mechanisms may only be dominant for specific stations and not applicable to the entire region.No single physical or ecological factors have been found to significantly influence the Chl distribution throughout the WAP region,which may be attributed to the heterogeneity of sea ice conditions,geometry and hydrodynamic features as well as variations in nutrient sources.

Decadal Changes in the Near-Surface Air Temperature in the Western Side of the Antarctic Peninsula

An analysis of the minimum air temperature behavior was carried out for the southern tip of South America and the western side of the Antarctica Peninsula. Punta Arenas shows an overall annual warming of 0.15°C per decade during the 1960-2010 period, although this occurred mainly in the summer and winter seasons. The trend of the air temperature in the western side of the Antarctic Peninsula shows an increase until around 2000, but the warming rate during the last 2001-2010 decade has been less than previous decades;in particular, meteorological stations in King George Island show slight cooling. The lineal annual warming per decade as shown by Bellingshausen, Verndsky/Faraday and Rothera stations are 0.26°C ± 0.75°C, 0.55°C ± 1.26°C and 0.69°C ± 1.31°C;for the respectively, 1969-2010, 1951-2010 and 1978-2010 periods. These rates of warming are slightly lower than those found for the same stations but for the 1969-2000, 1951-2000 and 1978-2000 periods.

Distinct impacts of two kinds of El Nino on precipitation over the Antarctic Peninsula and West Antarctica in austral spring

本文基于多种再分析资料,研究了中部型(CP)和东部型(EP)ElNino事件对南半球春季(9-11月)西南极和南极半岛降水的不同影响.结果显示,EP和CP事件对阿蒙森-别林斯高晋海的降水具有相似影响,而对威德尔海,特别是南极半岛的降水影响相反.由于EP事件激发两支罗斯贝波列,分别引起罗斯-阿蒙森-别林斯高森海和威德尔海上空的异常反气旋和气旋,从而导致别林斯高晋-威德尔海和南极半岛受到干冷的异常偏南风影响,降水减少.然而,CP事件仅激发一支相对较弱且偏西的罗斯贝波列,分别引起罗斯-阿蒙森海和别林斯高晋-威德尔海上空的异常反气旋和气旋,从而导致南极半岛以西(东)受异常偏南(北)风影响,降水减少(增加).

A note on crustal structure between Antarctic Peninsula and East Antarctic craton across the shelf of southern Weddell Sea

Analysis of gravity data based on the Airy isostasy, magnetic depth estimates and few seismic refraction data taken together indicates a thinning of the crust between the Antarctic Peninsula and the East Antarctic craton below the Filchner and Ronne ice shelves.

3D Gravity Inversion with Correlation Image in Space Domain and Application to the Northern Sinai Peninsula

We present a 3D inversion method to recover density distribution from gravity data in space domain.Our method firstly employs 3D correlation image of the vertical gradient of gravity data as a starting model to generate a higher resolution image for inversion.The 3D density distribution is then obtained by inverting the correlation image of gravity data to fit the observed data based on classical inversion method of the steepest descent method.We also perform the effective equivalent storage and subdomain techniques in the starting model calculation,the forward modeling and the inversion procedures,which allow fast computation in space domain with reducing memory consumption but maintaining accuracy.The efficiency and stability of our method is demonstrated on two sets of synthetic data and one set of the Northern Sinai Peninsula gravity data.The inverted 3D density distributions show that high density bodies beneath Risan Aniza and low density bodies exist to the southeast of Risan Aniza at depths between 1~10 and 20 km,which may be originated from hot anomalies in the lower crust.The results show that our inversion method is useful for 3D quantitative interpretation.

GRACE RL05-based ice mass changes in the typical regions of antarctica from 2004 to 2012

The Antarctic ice sheet is the largest block of ice on Earth, a tiny change of its ice sheet will have a significant impact on sea level change, so it plays an important role in global climate change. The Gravity Recovery and Climate Experiment （GRACE） mission, launched in 2002, provides an alternative method to monitor the Antarctic ice mass variation. The latest Release Level 05 （ RL05 ） version of GRACE time-variable gravity （TVG） data, derived from GRACE observations with improved quality and time-span over 10 years, were released by three GRACE data centers （CSR, JPL and GFZ） in April 2012, which gives us a chance to re-estimate the ice mass change over Antarctic more accurately. In this paper, we examine ice mass changes in regional scale, including Antarctic Peninsula （AP, West Antarctica）, Amundsen Sea Embayment （ASE, West Antarctica）, Lambert-Amery System （LAS, East Antarctica） and 27 drainage basins based on three data sets. The AP mass change rates are -12.03±0.74 Gt/a （CSR, 2004-2012）, -13.92±2.33 Gt/a （JPL, 2004 -2012） , -12.28±0.76 Gt/a （GFZ, 2005-2012） , with an acceleration of -1.50±0.25 Gt/a^2, -1.54±0.26 Gt/a^2, -0. 46±0.28 Gt/a^2 respectively, the ASE mass change rates are -89.22±1.93 Gt/a, -86.28± 2.20 Gt/a, -83.67±1.76 Gt/a with an acceleration of -10. 03±0. 65 Gt/a^2, -8.74±0. 74 Gt/a^2 and -5.69 ±0.68 Gt/a^2, and the LAS mass ehange rates are -4.31±1.95 Gt/a, -7.29±2. 84 Gt/a, 1.20±1.35 Gt/a with an acceleration of -0. 18±0.62 Gt/a^2, 3.55±0.95 Gt/a^2 and 0.97±0.49 Gt/a^2. The mass change rates derived from the three RL05 data are very close to each other both in AP and ASE with the uncertainties much smaller than the change rates, and mass losses are significantly accelerated since 2007 in AP and 2006 in ASE, respectively. However, the mass change rates are significantly different in LAS, negative rate from CSR and JPL data, but positive rate from GFZ data, the uncertainties are even larger than the correspondent change rates. With regard to the 27 drainage basins, seven basins （basin 3-9） located in the east Antarctica show positive mass change rates, and the rest twenty basins are characterized by negative mass change rates during the time span of the three RL05 data.

THE COMPILATION OF A DTM AND A NEW SATELLITE IMAGE MAP FOR KING GEORGE ISLAND,ANTARCTICA

An improved topographic database for King George Island,one of the most frequently visited regions in Antarctica,is presented.A first step consisted in combining data from differential GPS surveys gained during the austral summers 1997～1998 and 1999～2000,with the current coastline from a SPOT satellite image mosaic,topographic information from existing maps and from the Antarctic Digital Database.From this data sets,a digital terrain model (DTM) was generated using Arc/Info GIS.In a second step,a satellite image map at the scale 1∶100 000 was assembled from contour lines derived from the DTM and the satellite mosaic.A lack of accurate topographic information in the eastern part of the island was identified.Additional topographic surveying or SAR interferometry should be used to improve the data quality in that area.The GIS integrated database will be indispensable for glaciological and climatological studies and administrative and scientific purposes.In future,the application of GIS techniques will be mandatory for environmental impact studies and environmental monitoring as well as for management plans on King George Island.

Mesozoic and Cenozoic microbiotas from eastern Antarctic Peninsula: adaptation to a changing palaeoenvironment

A compiled selected literature on some groups of microfossils of the Mesozoic and Cenozoic of the James Ross Basin,eastern Antarctic Peninsula,is presented here,in order to show how the microbiota has been modified over time,triggered by environmental changes.The analyzed microfossils consist of palynomorphs(mostly pollen grains,spores,and dinoflagellate cysts),foraminifers and bryozoans.Dinoflagellate cysts and pollen-spores have been recorded in Jurassic to Pleistocene sedimentary outcrops.Dinoflagellate cysts proved to be good indicators for productivity and/or nutrient availability,surface water temperature and chemistry,the position of ancient shorelines and paleoceanographic trends.Pollen and spores allowed reconstruction of floral community and thus characterization of the climate that prevailed on the continent.Foraminifera,recovered from the Lower Cretaceous to the Pleistocene sedimentary rocks,provided information about the bathymetry,showing different marine settings(e.g.,coastal,inner neritic,outer neritic,upper bathyal)in different localities.The bryozoan record is restricted to the Cenozoic.Their colonial growth-forms reflect several environmental conditions such as shallow waters with a low rate of sedimentation,hard substrate and moderate or strong current action for the analyzed localities.The study of the Antarctic ecosystems based on the fossil microbiota and their response to the climate and the continental configuration changes,allowed understanding of the composition and dynamics of the polar environments,which have an important role in the Earth climate.

Distribution of polychaetes in the shallow, sublittoral zone of Admiralty Bay, King George Island, Antarctica in the early and late austral summer

This study assessed the spatial distribution pa- ttern of soft-sediment polychaetes on the near-shore of Admiralty Bay, King George Island, Antarctica. In the early and late summer of 2003 /04, seven sites at three different depths (20,30 and 60 meters) were sampled using a van Veen grab. 8,668 individuals all told, belonging to 67 species and 23 families, were identified. The families Terebellidae, Syllidae and Maldanidae were the most speciose. Mean densities ranged from 45.2 to 388.1 ind. 0.1 m-2 in the early summer, and from 29 to 183 ind.0.1m-2 in the late. The species Aphelochaeta cincinnata, Levinsenia gracilis and Rhodine antarctica were the most frequent and abundant. Initially, mean biomass ranged from 0.11 to 5.27 g.0.1 m-2, in the early season and from 0.35 to 5.86 g.0.1 m-2 towards the end. Aglaophamus trissophyllus, Eupolymnia sp. and Barrukia cristata were the species with the highest biomass. Polychaete taxocoenosis structure remained similar in both periods. In the early summer, mean densities, biomass and number of species were lower at 30 meters and higher at 60, whereas in the late, these differences were higher among transects. Ice impacts, mainly anchor-ice, in the early summer, as well as icebergs later on, most likely caused the differences encountered.