The evolution of biogeochemistry, retraces the important historical steps in part, covered by Gorham (Biogeochemistry 13:199–239, 1991) in the 18–19th centuries—with new emergent linkages and trends in 20–21st centuries. In the post-phlogiston period, key synthetic connections are made between weathering, atmospheric chemistry, carbon cycling, and climate change. Early work in the 19th century, focused on weathering and the importance of organisms in the exchange of carbon dioxide between the rocks and the atmosphere, provided foundations for new analytical approaches. The role microbes in connecting abiotic and biotic processes begins to emerge, based largely on the existing knowledge of stoichiometry in agricultural soils and plants. This in part, leads to the founding of ecology and its linkages with evolution and biogeography. Verandsky boldly emerges in the 20th century, with his concepts of a biosphere and a noosphere, as concerns begin to arise about human impacts on nature. The development of organic geochemistry as a discipline, allowed for new roots to develop in the evolution of biogeochemistry through linkages between short and long-term carbon cycles. In the 20th century, a new interesting stoichiometry emerges in biogeochemistry—as related to the Green Revolution, human population growth, and eutrophication problems. The advent of long-term and large-scale experiments help to constrain the complexity of non-linearity and regional differences in fluxes and rates in biogeochemical work. A new age begins in the 21st century whereby molecular approaches (e.g. omics) combined with large-scale satellite, monitoring, survey, observatory approaches are combined in the development of Earth System models. These new connections with ecological/evolutionary genetics are one of the more dramatic and important aspects of biogeochemistry in modern times.

In this article, we analyze the impacts of climate change on Antarctic marine ecosystems. Observations demonstrate large-scale changes in the physical variables and circulation of the Southern Ocean driven by warming, stratospheric ozone depletion, and a positive Southern Annular Mode. Alterations in the physical environment are driving change through all levels of Antarctic marine food webs, which differ regionally. The distributions of key species, such as Antarctic krill, are also changing. Differential responses among predators reflect differences in species ecology. The impacts of climate change on Antarctic biodiversity will likely vary for different communities and depend on species range. Coastal communities and those of sub-Antarctic islands, especially range-restricted endemic communities, will likely suffer the greatest negative consequences of climate change. Simultaneously, ecosystem services in the Southern Ocean will likely increase. Such decoupling of ecosystem services and endemic species will require consideration in the management of human activities such as fishing in Antarctic marine ecosystems.

The CO uptake by the Southern Ocean (<35°S) varies substantially on all timescales and is a major determinant of the variations of the global ocean carbon sink. Particularly strong are the decadal changes characterized by a weakening period of the Southern Ocean carbon sink in the 1990s and a rebound after 2000. The weakening in the 1990s resulted primarily from a southward shift of the westerlies that enhanced the upwelling and outgassing of respired (i.e., natural) CO. The concurrent reduction in the storage rate of anthropogenic CO in the mode and intermediate waters south of 35°S suggests that this shift also decreased the uptake of anthropogenic CO. The rebound and the subsequent strong, decade-long reinvigoration of the carbon sink appear to have been driven by cooling in the Pacific Ocean, enhanced stratification in the Atlantic and Indian Ocean sectors, and a reduced overturning. Current-generation ocean models generally do not reproduce these variations and are poorly skilled at making decadal predictions in this region.

The Southern Ocean, a region highly vulnerable to climate change, plays a vital role in regulating global nutrient cycles and atmospheric CO via the biological carbon pump. Diatoms, photosynthetically active plankton with dense opal skeletons, are key to this process as their exoskeletons are thought to enhance the transfer of particulate organic carbon to depth, positioning them as major vectors of carbon storage. Yet conflicting observations obscure the mechanistic link between diatoms, opal and particulate organic carbon fluxes, especially in the twilight zone where greatest flux losses occur. Here we present direct springtime flux measurements from different sectors of the subpolar Southern Ocean, demonstrating that across large areas of the subpolar twilight zone, carbon is efficiently transferred to depth, albeit not by diatoms. Rather, opal is retained near the surface ocean, indicating that processes such as diatom buoyancy regulation and grazer repackaging can negate ballast effects of diatoms' skeletons. Our results highlight that the presence of diatoms in surface waters of the Southern Ocean's largest biome does not guarantee their importance as vectors for efficient carbon transfer through the subpolar twilight zone. Climate change-driven shifts in phytoplankton community composition may affect biologically sequestered carbon pools less than currently predicted.© The Author(s) 2024.

Southern Ocean primary productivity is principally controlled by adjustments in light and iron limitation, but the spatial and temporal determinants of iron availability, accessibility, and demand are poorly constrained, which hinders accurate long-term projections. We present a multidecadal record of phytoplankton photophysiology between 1996 and 2022 from historical in situ datasets collected by Biogeochemical Argo (BGC-Argo) floats and ship-based platforms. We find a significant multidecadal trend in irradiance-normalized nonphotochemical quenching due to increasing iron stress, with concomitant declines in regional net primary production. The observed trend of increasing iron stress results from changing Southern Ocean mixed-layer physics as well as complex biological and chemical feedback that is indicative of important ongoing changes to the Southern Ocean carbon cycle.

The carbon sequestration potential of open-ocean pelagic ecosystems is vastly under-reported compared to coastal vegetation 'blue carbon' systems. Here we show that just a single pelagic harvested species, Antarctic krill, sequesters a similar amount of carbon through its sinking faecal pellets as marshes, mangroves and seagrass. Due to their massive population biomass, fast-sinking faecal pellets and the modest depths that pellets need to reach to achieve sequestration (mean is 381 m), Antarctic krill faecal pellets sequester 20 MtC per productive season (spring to early Autumn). This is equates USD$ 4 - 46 billion depending on the price of carbon, with krill pellet carbon stored for at least 100 years and with some reaching as far as the North Pacific. Antarctic krill are being impacted by rapid polar climate change and an expanding fishery, thus krill populations and their habitat warrant protection to preserve this valuable carbon sink.© 2024. The Author(s).

本文利用中国第25次南极科学考察数据，运用数学模型对南极普里兹湾有机碳与无机碳的分解比及上层水体POC的再矿化效率进行了估算。结果表明:普里兹湾及其邻近海域POC的浓度范围为24.38~446.40&mu;g?dm-3，平均值为118.16&mu;g?dm-3。在普里兹湾P2断面陆架区，上层水体中的有机碳和无机碳向下层水体输出埋藏过程中，两者分解速率比为1.27（摩尔比），根据相关结果我们推测上层水体中的颗粒有机碳向底层输出埋藏的过程中有81%发生了转化重新参与海洋碳循环。

在中国第24次和第25次南极科学考察期间，利用航渡表层水观测和普里兹湾定点观测，对颗粒有机碳(POC)的分布及其影响因素进行了研究。结果表明，南大洋表层水体的颗粒有机碳分布具有明显的区域性特征，表层水体POC的含量与营养盐和叶绿素a有着明显的相关分布趋势。南极水、亚南极水的表层POC浓度明显高于亚热带水和热带水，第24次南极科学考察期间亚热带和热带水、亚南极水和南极水的表层POC平均浓度为78.03，116.59和105.8 &mu;g&middot;dm^-3，要略高于第25次南极科学考察的49.36，59.39和71.54 &mu;g&middot;dm^-3，南大洋表层POC的年季变化，受多种因素的影响。第24次和第25次南极科学考察中普里兹湾及其邻近海域POC的浓度范围分别为12.78&mdash;363.73 &mu;g&middot;dm^-3和24.38&mdash;446.40 &mu;g&middot;dm^-3，表层分布主要表现出湾内高、湾外低的特点。湾内陆架区、陆坡区和湾外深水区的POC与Chl a都具有良好的正相关关系，相关系数R值分别为0.8248，0.8049和0.6989，说明POC主要来源于浮游生物的贡献。并且，在POC的垂直分布上，受到光照、营养盐及海流等各种因素的影响，在物理和生物的相互耦合作用，致使POC的最大值有从湾内的表层最大值向湾外的次表层最大值转变的趋势。

The concentrations and distributions of particulate biogenic silica (PBSi) in the upper surface waters of Prydz Bay, Antarctica, were investigated during the 27th Chinese National Antarctic Research Expedition cruises of January 2011. We aimed to characterize the correlations between PBSi and plankton, nutrients and particulate organic carbon. The results showed that the concentrations of biogenic silica ranged from 0.76-19.72 μmol•dm^-3 and the average concentration of biogenic silica was6.06 μmol•dm^-3. The distribution of surface PBSi had significant regional characteristics: The concentrations were higher south of 67°S than to the north. The distribution of PBSi, chlorophyll a and particulate organic carbon showed similar patterns, and PBSi distribution had a negative correlation with that of silicate. In the vertical direction, the mole ratio of PBSi and POC (Si_bio/C_org) decreased with increasing depth. This trend indicated a higher rate of PBSi dissolution, or a lower rate of organic matter remineralization rate, in the upper 200 m.

利用中国第24次南极考察获得的水样,研究了普里兹湾表层海水中痕量元素铜、镉、锌的含量及其分布。原子吸收分光光度法(AAS)测得普里兹湾铜、镉、锌的浓度范围分别为0&middot;36&mdash;2.86、0.020&mdash;0.594、2.9&mdash;20.0&mu;g&middot;dm-3,平均值分别为1.15、0.143、11.2&mu;g&middot;dm-3。发现普里兹湾表层海水中铜、镉、锌的含量与南印度洋、南极海洋气溶胶及LarsemannHills湖泊群水体中的含量近似。研究表明,表层海水中铜、镉的含量及分布受悬浮颗粒物、初级生产力及盐度等的影响,锌可能受到了一定程度的人类活动的影响。

在中国第22次南极科学考察期间, 通过南大洋普里兹湾150 m上表层水柱采集的浮游植物的现场培养实验, 研究了湾内陆架区III-11站与埃默里冰架边缘区IS-2站浮游植物颗粒物的降解过程, 估算了实验条件下研究海域浮游植物碎屑耗氧速率以及营养盐的生成速率。结果表明: 在实验初期DO含量变化明显, 随时间呈显著下降趋势, 而营养盐含量则呈上升趋势, 两者在实验后期均变化缓慢。在III-11站100 h内耗氧速率为92.592 mg/(m²&middot;h), 实验初期磷酸盐、铵盐以及硅酸盐的生成速率分别为: 107.15, 65.10, 351.93 &mu;mol/(m²&middot;h)；在IS-2站50 h内耗氧速率为77.927 mg/(m²&middot;h), 50 h后耗氧速率降为21.142 mg/(m²&middot;h), 50 h内磷酸盐、铵盐以及硅酸盐的生成速率分别为: 43.61, 137.32, 60.89 &mu;mol/(m²&middot;h)。

Speciation of phosphorus in surface sediments which were collected during several CHINARE cruises in Prydz Bay were investigated. The sequential extraction method(SEDEX) was used to separate and quantify the following five sedimentary P reservoirs: exchangeable phosphorus (ExP), iron phosphorus (FeP), authigenic phosphorus (AuP), detritus phosphorus (DeP) and organic phosphorus (OP). DeP and AuP were the major types of phosphorus in surface sediments, with an average of 37.5% and 25.8% to total P. The obvious positive relationships between OP, AuP and OC, Sibio indicated that they might come from the same source which was mainly from marine biogenic matters. DeP could be observed positively correlated with Al and sandy sediments, which preferences land sources that might be carried by sea ice with current. It was shown that the content and distributions of P in sediments were majorly controlled by the sources of P, also included the grain size of sediments and other physical factors such as sea ice and current．ExP was controlled by grain size of sediments, while FeP was controlled by iron. In addition, either ExP or FeP was a small components in total phosphorus, only 8.9% and 6.5% respectively. Bioavailable phosphorus concentrated in the central and eastern region, with an average content of 37.2% to total P.

Multiple biomarkers has been analyzed by gas chromatography and gas chromatography &ndash; mass spectrum on surface sediments collected from 5 stations in Prydz Bay, East Antarctica, and its implication on ecology and environment has been discussed. The results showed that the concentration of total lipids was highest in the center area of Prydz Bay (1193 &micro;g/g), follow by Amery Ice Shelf area (572 &micro;g/g), and lowest in slope area (341 &micro;g/g). It was significantly positive correlated with sedimentary organic carbon, total neutral monosaccharides, biogenic silica, brassicasterol, and chlorophyll a concentrations in surface sea water (<em>p</em> < 0.1), and indicated that organic matter preserved in surface sediment was mainly from marine phytoplankton. The significantly negative correlation of relative concentrations between C₂₇ and C₂₈ steranes showed the food chain between <em>Euphausia crystallorophias</em> and diatoms. The relative high ratio of saturated hydrocarbons : arenes (> 2.5), low ratios of Pr/C₁₇ (< 0.5) and Pr/Ph (< 2) inferred the sedimentary organic matter was largely contributed by diatoms. Meanwhile, the double peak of saturated hydrocarbons (C₁₇ or C₁₈, C₂₉) and relative high concentration of C₂₉ steranes (35.79%) showed terrestrial vascular plants input, and it was higher in the center area of Prydz Bay (CPI = 1.60, Pr/Ph = 1.01) than the slope area and Amery Ice Shelf area (CPI = 0.69, Pr/Ph = 0.39). The ratio of C_18:2/C_18:0 for fatty acids was higher in sediment collected from the center area and Amery Ice Shelf area of Prydz Bay (0.78) than that from slope area of Prydz Bay (0.23) and lower latitude regions (< 0.1), and indicated that during austral summer, the surface sea temperature was higher in slope area of Prydz Bay than center area of Prydz Bay and Amery Ice Shelf area.

利用中国南极考察获取的沉积物样品,对普里兹湾10个表层沉积物中GDGTs的含量与分布进行分析。结果表明:普里兹湾内GDGTs含量为27.69~900.78 ng/g,其中类异戊二烯GDGTs占比94%~99%,远高于支链GDGTs。类异戊二烯GDGTs与支链GDGTs都呈现东南高、西北低的分布趋势,且与沉积物中有机碳含量显著正相关(R>0.95)。沉积物中类异戊二烯GDGTs来源于水生古菌,而支链GDGTs主要来源于沉积物中的细菌。根据GDGTs不同异构体含量计算得到的指标TEX₈₆和TEX^L₈₆都与普里兹湾1月表层海水温度呈现良好的相关性。这表明TEX₈₆和TEX^L₈₆指标在普里兹湾海域具有适用性,可以作为重建古海温的替代指标。

A number of major and trace elements including C, N, Ca, and Al were measured in 20 surface sediment samples collected from Prydz Bay, Antarctica, during the CHINARE 18&ndash;27 cruises. The distributions of these elements and their characteristics of association were used to explore the sedimentary environment and material sources within the study area. The results showed that the values of most of the elements in the surface sediments changed over a wide range. Furthermore, the elemental distribution, correlation, and clustering features presented two patterns. One represented by OC, TN, and S that indicated a source of marine organisms, and the other represented by K, Ti, and Rb that indicated a source of terrigenous clastics. The results also suggested that sedimentation at the center of Prydz Bay and the southeastern area was controlled by biological production, whereas sedimentation near the Fram Bank and continental shelf in front of the Amery Shelf, contained a large number of ice-rafted clasts.

The content and distribution of Ge is investigated in sediments from the Southern Ocean (Prydz Bay, Antarctica). Thecontent of Getotal in the sediments ranges from 1.14×10^-6 to 2.35×10^-6 (average of 1.71×10^-6) and the highest value occurs at stationP3-9 where water depth is > 1 000 m. The lowest value occurs at station P4-13 which is near the edge of the Amery ice shelf. Thesurface sediments have 16%–68% Ge_bio within Getotal. The distribution trends of Ge_bio and Getotal are generally similar, and the valuesoutside Prydz Bay are higher than within the bay, bounded at 67°S. The vertical distribution of Ge in sediment cores presentshigher values at the surface than in underlying sediments. Values of Ge_bio appear to positively correlate with biogenic silica (BSiO₂)in surface sediments from non-polynyas sea. The vertical distribution of Ge_bio and BSiO2 is similar in sediments of station P3-16.

Concentrations of biogenic barium were investigated in surface sediments of Prydz Bay, Antarctica, during the 21st and 27th CHINARE cruises. Factors controlling the observed distribution are explored. Biogenic barium concentrations obtained from a sequential extraction procedure are compared with total concentrations obtained from the normative calculation based on a total digestion, and differences in the results are examined. Concentrations of biogenic barium, calculated by the normative calculation, were much higher than the concentrations obtained through sequential extraction; this discrepancy is the result of the occurrence of barium associated with Mn/Fe oxides, which represents an important component of total barium in these sediments. Concentrations of biogenic barium obtained from the sequential extraction range from 104 to 445 μg·g^-1, and the average concentration was 227 μg·g^-1. The highest concentrations of biogenic barium occur in the central area of the bay, where the seawater is more stable, while lower values occur in the bank and the ice shelf. Biogenic barium is significantly linearly correlated with biogenic barium and organic carbon, and similar in distribution of Chl a, which may indicate that primary productivity of phytoplankton in the surface water column is the main environmental factor regulating barium concentration and distribution.

<p>Nutrient data collected in Prydz Bay during the CHINARE 25/27/29 cruises were analyzed to study the<br>distribution pattern of nutrient concentrations. The consumption, absorption ratio, and structure of nutrients<br>(NNU, NPU, and NSiU) in summer were evaluated based on the existence of the Tmin layer. The results<br>showed that the spatial distributions of nutrient concentrations in the surface waters of Prydz Bay had obvious<br>regional characteristics. The highest, intermediate, and lowest concentrations of nutrients were observed<br>in the open sea, continental shelf, and marginal ice shelf areas, respectively. Consumption of nutrients in<br>inner areas of Prydz Bay was higher than outer areas partly because of the influence of the phytoplankton<br>bloom in austral summer; a period in which nutrients are absorbed by phytoplankton for photosynthesis. The<br>NSiU/NNU ratios showed distribution patterns similar to nutrient concentrations but opposite to Chla concentration.<br>It is speculated that this difference is mainly due to the higher supply of iron in the continental<br>shelf region and inner Prydz Bay area comparted with the open sea. Investigation of the structure and<br>changes of nutrient concentrations in Prydz Bay can help us better understand the biogenic element cycle<br>processes in the Southern Ocean and provide a basis for predicting the evolution of phytoplankton structure<br>in the Southern Ocean.</p>

Siliceous microplankton is an effective proxy for connecting modern and past marine environments; however, radiolarians have been understudied in Prydz Bay, Eastern Antarctica. This study investigated the changes in the siliceous microbiota fluxes and radiolarian assemblages captured in a 1-year time-series sediment trap (February 2014 to February 2015, ~490 m water depth) in the polynya of Prydz Bay. The results exhibited the strong seasonality in the radiolarian assemblages and the fluxes of radiolarians, diatoms, silicoflagellates and sponge spicules, with low numbers in winter and high numbers in summer. Seasonal variations in the sea ice and plankton community were critical in these patterns. The total radiolarian flux (TRF) displayed three peaks with higher flux than the annual average TRF over the year, all of which occurred in summer. These TRF peaks were mainly driven by seasonal fluctuations of sea ice, primary productivity, grazing pressure caused by phytophagous zooplankton and resuspension of small radiolarians in the surface sediments induced by modified Circumpolar Deep Water (mCDW) intrusion onto the shelf. There were also two notable low-TRF stages, mainly related to full sea-ice coverage and high grazing pressure. Two dominant assemblages were recognized by means of Q-factor analysis. Dominant assemblage one was composed of three small-sized taxa,Antarctissasp.,Phormacantha hystrixandPlectacantha oikiskos, which could be used as a proxy for primary productivity in the Marginal Ice Zone (MIZ) in Prydz Bay. Dominant assemblage two was composed ofAntarctissa strelkoviandAntarctissa denticulata, withA. strelkovidominating. The high flux and high relative abundance ofA. strelkovimarked the extension of Ice Shelf Water (ISW) to the shelf area in Prydz Bay. These findings will provide new insights and reliable proxies for modern and paleoceanographic research in the Southern Ocean.

Examining iron (Fe) speciation in marine sediments is critical to understand Fe and carbon biogeochemical cycling in polar regions. In this study, we investigated the speciation of Fe in sediments from Prydz Bay and the adjacent Southern Ocean, and examined the factors controlling Fe speciation and its relationship with total organic carbon (TOC). Our results reveal that unreactive silicate Fe (FeU) is the dominant pool of total Fe (FeT), followed by poorly reactive sheet silicate Fe (FePRS), reducible crystalline Fe oxides (Feox2), easily reducible amorphous/poorly crystalline Fe oxides (Feox1), and magnetite (Femag), with carbonate-associated ferrous Fe (Fecarb) being the smallest pool. The highly reactive Fe (FeHR)/FeT ratios (0.13 ± 0.06) in our study area are among the lowest end-member globally, primarily due to weak bedrock weathering and slow glacier melting. The Feox1/FeT ratios are similar to those in continental shelf and marginal seas containing highly weathered materials, while the Feox2/FeT ratios are significantly lower. This result implicates that low temperature inhibits the aging of iceberg melting-sourced Feox1 potentially, and accordingly the regulation of weathering on the FeHR/FeT ratio is mainly reflected in Feox2/FeT ratio. There are no significant correlations between TOC and FeHR, Fecarb, Feox1 or Feox2 in the research region. Four distinct patterns of TOC/FeHR ratio can be discerned by summarizing the global data set: (a) high TOC/FeHR ratios (&gt; 2.5) are likely the result of high marine primary productivity and low chemically weathered source materials; (b) low TOC/FeHR ratios (&lt; 0.6) are caused by high rates of FeHR inputs and OC remineralization; (c) mid-range TOC/FeHR ratios (0.6 – 2.5) typical of most river particulates and marginal sea sediments indicate the same FeHR and OC sources and/or interactions between each other; (d) both low TOC and FeHR content is the result of low marine primary productivity and weak chemical weathering. Our findings provide new insights into the relationship between FeHR and TOC in polar sediments.

<p>Particulate organic carbon (POC) is an important material and energy source for the marine food chain. Because of its close relationship with life processes and primary productivity, its distribution can effectively provide information on the biogeochemical environment. During the 33rd CHINARE that took place between December 2016 and January 2017, suspended particulate matter samples were collected from the ocean adjacent to the Antarctic Peninsula to study POC distribution and factors influencing POC distribution. In the Scotia Sea, POC concentrations were between 7.44 and 193.52 &mu;g&middot;L^&minus;1, with a mean value of 48.84&plusmn;35.09 &mu;g&middot;L^&minus;1; over South Scotia Ridge, concentrations were between 9.13 and 62.17 &mu;g&middot;L^&minus;1, with a mean value of 29.76&plusmn;14.12 &mu;g&middot;L^&minus;1; in Powell Basin, concentrations were between 5.87 and 270.72 &mu;g&middot;L^&minus;1, with a mean value of 48.57&plusmn;38.92 &mu;g&middot;L^&minus;1. In surface waters, high concentrations were found in Scotia Sea and Powell Basin while low concentrations were found over South Scotia Ridge; these results are consistent with variations in chlorophyll-a concentration, but are opposite to those in nutrient concentration. Concentrations of POC decreased with depth. In Powell Basin and Scotia Sea, the highest POC concentrations were found between the surface and a depth of 25 m. Results from principal component analysis show that photosynthetic phytoplankton is the main source of POC in the study area. Concentrations of POC were affected by temperature, water mass mixing and melting sea ice. Proportions of non-living POC were low over South Scotia Ridge; they were high in Scotia Sea and Powell Basin because of high krill biomass, sea ice debris and input from land-based sources.</p>

南乔治亚岛海域是南大洋初级生产力最高的区域之一,具有巨大的固碳潜力,但由于缺乏连续的上层海洋观测资料,该海域生物泵效率的强弱仍未有定论。本研究利用2017年至2020年期间位于南乔治亚岛附近海域的生物地球化学浮标(BGC-Argo)所获取的水文和生物化学参数,探讨了物理过程对生物地球化学过程的影响,并估算了该海域的南极夏季碳输出通量。结果显示:南乔治亚岛上游(南极半岛东北部)和下游(乔治亚海盆)海域Chl-a均呈现出很强的季节性特征,尤其是乔治亚海盆区浮游植物维持了4个月的旺发时间,表明该区域具有稳定持续的铁源供给;利用颗粒有机碳(POC)季节性输出量的时间变率,估算了上、下游的夏季POC输出通量分别为7.12±3.90 mmol·m^-2·d^-1和45.29±5.40 mmol·m^-2·d^-1,推测这种差异主要是由于混合层加深后促进了有机碳的向下输出导致的。研究发现该区域维持着较高的生物泵效率,与此前的乔治亚海盆存在“高生产力低输出效率”的结论不同,这可能是由于航次断面调查的即时性无法反映整个季节性特征所造成的。BGC-Argo能提供高时空分辨率的多参数观测数据,本研究结果表明其可以更准确地量化与评估海洋生物地球化学过程和固碳能力。

The waters surrounding South Georgia Island are one of the highest primary productivity regions in the Southern Ocean with enormous carbon sequestration potential. However, the strength of the biological pump efficiency in this area is still uncertain due to the lack of continuous upper ocean observation data.In this study, the hydrological and biogeochemical parameters obtained from the Biogeochemical Argo (BGC-Argo) floats deployed in the South Georgia Island vicinity during the period of 2017-2020 were utilized to investigate the impacts of physical processes on biogeochemical processes and to estimate the carbon export flux in the Antarctic summer. Results indicated that both upstream (northeast of the Antarctic Peninsula) and downstream (Georgia Basin) regions of South Georgia Island exhibited strong seasonal characteristics in Chl- a, with the latter area having a 4-month sustained period of phytoplankton bloom, suggesting a stable and continuous supply of iron. Using the temporal variability of the seasonal particulate organic carbon (POC) export, the summer POC export fluxes of the upstream and downstream regions were estimated to be 7.12±3.90 mmol·m^-2·d^-1 and 45.29±5.40 mmol·m^-2·d^-1, respectively, indicating that the difference might be due to enhanced downward export of organic carbon after the deepening of the mixed layer. The study found that the region maintained a high biological pump efficiency, contrary to the previous conclusion that the Georgia Basin had “high productivity low export efficiency”, which might have been caused by the limited “real-time” representation of the entire seasonal characteristics during ship-based surveys. BGC-Argo provides high spatiotemporal resolution of multi-parameter observation data, and this study demonstrates that it can more accurately quantify and evaluate marine biogeochemical processes and carbon sequestration potential.

通过分析罗斯海15个表层沉积物中甘油双烷基甘油四醚(Glycerol Dialkyl Glycerol Tetraethers,GDGTs)的含量与分布,探讨了各种GDGTs来源及TEX₈₆指标的环境意义。结果表明:表层沉积物中GDGTs总含量为93.67~2 663.37 ng/g,其中类异戊二烯GDGTs(IsoGDGTs)占90.33%~98.56%,远高于支链GDGTs(BrGDGTs)。类异戊二烯GDGTs与支链GDGTs具有显著的耦合关系(R²=0.88,p<0.01)。沉积物中的IsoGDGTs主要来源于海洋奇古菌,BrGDGTs主要由海洋水体和沉积物中原位细菌所产生。应用TEX^L₈₆公式估算研究区SST,与WOA夏季表层温度呈现较好的线性关系,表明TEX^L₈₆指标在罗斯海具有适用性,可作为重建古海洋温度的替代指标。

Organic carbon (OC) burial in the Antarctic marginal seas is essential for regulating global climate, particularly due to its association with ice shelf retreat. Here, we analyzed total OC (TOC), total nitrogen (TN), radiocarbon isotope, n-alkanes and relative indicators in surface and core sediments from the Ross Sea, West Antarctica. Our aim was to investigate spatial and historical changes in OC sources, and to explore the influencing factors and implications for ice shelf retreat since the last glacial maximum (LGM). Our results revealed distinct spatial patterns of OC sources as indicated by n-alkane indicators in surface sediments. In the Western Ross Sea, n-alkanes predominantly originated from phytoplankton and bacteria, as evidenced by their unimodal distribution, low carbon preference index (CPI) of short-chain n-alkanes (CPIL = 1.41 ± 0.30), and low terrestrial/aquatic ratio (TAR = 0.22 ± 0.14). In the Southwest Ross Sea, n-alkanes were derived from marine algae and terrestrial bryophytes, indicated by bimodal distribution, low ratio of low/high molecular-weight n-alkanes (L/H = 0.62 ± 0.21), low CPI of long-chain n-alkanes (CPIH = 1.18 ± 0.16), and high TAR (1.26 ± 0.66). In contrast, the Eastern Ross Sea exhibited n-alkanes that were a combination of phytoplankton and dust from Antarctic soils and/or leaf waxes from mid-latitude higher plant, as suggested by both unimodal and bimodal distributions, high L/H (1.60 ± 0.58) and CPIH (2.04 ± 0.28), and medium TAR (0.61 ± 0.30). Geologically, during the LGM (27.3 – 21.0 ka before present (BP)), there was an increased supply of terrestrial OC (TOC/TN = 13.63 ± 1.29, bimodal distribution of n-alkanes with main carbon peaks at nC17/nC19 and nC27). From 21.0 to 8.2 ka BP, as glaciers retreated and temperatures rose, the proportion of marine n-alkanes significantly increased (TOC/TN = 9.09 ± 1.82, bimodal distribution of n-alkanes with main carbon peaks at nC18/nC19 and nC25). From 8.2 ka BP to the present, as the ice shelf continued to retreat to its current position, the marine contribution became dominant (TOC/TN = 8.18 ± 0.51, unimodal distribution of n-alkanes with main carbon peak at nC17/nC18/nC19, and low TAR (0.41 ± 0.32)). This research has significant implications for understanding the variations in Antarctic OC sources and their climatic impacts in the context of accelerated glacier melting.

Sea ice melt water and circumpolar deep water (CDW) intrusion have important impacts on the ecosystem of the Amundsen Sea. In this study, samples of nutrients and phytoplankton pigments from nine stations in the eastern Amundsen Sea were collected during the austral summer. Based on in-situ hydrological observations, sea ice density data from satellite remote sensing, and chemical taxonomy calculations, the relationships between environmental factors and phytoplankton biomass and community structure were studied. The results showed that with increasing latitude, the contribution of sea ice melt water (MW%) and the stability of the water body increased, and the depth of the mixed layer (MLD) decreased. The integrated concentration of chlorophyll <i>a</i> (Chl-<i>a</i>) ranged from 21.4 mg•m⁻² to 148.4 mg•m⁻² (the average value was 35.7±53.4 mg•m⁻²). Diatoms (diatoms-A [<i>Fragilariopsis</i> spp., <i>Chaetoceros</i> spp., and <i>Proboscia</i> spp.] and diatoms-B [Pseudonitzschia spp.]) and <i>Phaeocystis antarctica</i> were the two most widely distributed phytoplankton groups and contributed 32%±16% and 28%±11%, respectively, of the total biomass. The contributions of Dinoflagellates, Chlorophytes, Cryptophytes, the high-iron group of <i>P. antarctica</i>, and Diatom group A were approximately 17%±8%, 15%±13%, 9%±6%, 5%±9%, and 3%±7%, respectively. The area with the highest phytoplankton biomass was located near the ice-edge region, with a short time lag (T_lag) between sampling and complete sea ice melt and a high MW%, while the area with the second-highest Chl-<i>a</i> concentration was located in the area affected by the upwelling of CDW, with thorough water mixing. Vertically, in the area with a short T_lag and a shallow MLD, the phytoplankton biomass and proportion of diatoms decreased rapidly with increasing water depth. In contrast, in the region with a long T_lag and limited CDW upwelling, the phytoplankton community was dominated by a relatively constant and high proportion of micro phytoplankton, and the phytoplankton biomass was low and relatively stable vertically. Generally, the phytoplankton community structure and biomass in the study area showed high spatial variation and were sensitive to environmental changes.

Zooplankton are critical components of the Southern Ocean ecosystems, acting as trophic links between phytoplankton and higher-level species. The composition, abundance, carbon biomass, and community structure of zooplankton were studied based on samples collected with a Norpac net (330-µm mesh, 0.5-m2 net mouth) during the austral summers of 2017/2018. Three communities in a latitudinal gradient were identified based on both a zooplankton abundance dataset and a biomass dataset. Zooplankton were mainly dominated by small copepods (e.g., Oithona similis and Ctenocalanus citer) in terms of abundance, while the total zooplankton biomass was dominated by krill (Euphausia superba and Thysanoessa macrura) and large copepods (e.g., Calanoides acutus, Calanus propinquus, and Metridia gerlachei). Redundancy analysis demonstrated that environmental factors (e.g., temperature, nitrate, dissolved oxygen, ammonium) accounted for more than 40% of the variance in zooplankton abundance/biomass. This indicates that physical processes significantly affect the zooplankton community. Meanwhile, a significant positive correlation was found between the abundance/biomass of zooplankton and that of dominant phytoplankton and ciliates, which suggests trophic links among various plankton functional groups. Our results reveal that both physical processes and biological factors shape the community structure of zooplankton in the Amundsen Sea.

对西南极乔治王岛西湖沉积物XH1柱样进行了²¹⁰Pb测年, 建立起百余年(1885~2006年)沉积地层序列。定量分析了该柱样中的正构烷烃、脂肪酸和甾醇等类脂生物标志物, 综合研究了其分子组合特征和大尺度气候事件[厄尔尼诺-南方涛动(ENSO)和南半球环状模(SAM)]指标, 探讨了湖泊沉积有机质来源、沉积环境和早期成岩作用及其与生态环境变化的关系。结果表明, 正构烷烃的主峰碳(nC₂₃)、脂肪酸的后主峰碳(C_24:0)、较高的C₂₉甾醇含量和较低的SC₂₁^–/SC₂₂⁺比值均显示, 苔藓、地衣等低等陆生植物是西湖沉积物中有机质的主要来源, 而水生动植物及微生物的贡献相对较少。脂肪酸C_18:2/C_18:0比值表明, 在年代际时间尺度上, 与ENSO相比, SAM对南极半岛生态系统可能更具影响力, 且对湖泊水生动植物的影响比陆生植物更为明显。内源输入的甾醇指标ACI显示, 西风变弱、南极半岛变暖时, 沉积物中水生生物贡献的有机质减少。整体而言,过去的100多年中, 西湖呈弱氧化的沉积环境, 早期成岩作用较弱, 且气候事件对湖泊沉积环境影响不大。

The investigation of patterns of biogenic elements in the Antarctic marine environment and their ecological and environmental effects is crucial for understanding global climate change, carbon cycling, and interactions within ecosystems. It also provides a scientific foundation for predicting the evolutionary patterns of the Southern Ocean ecosystem. Since inaugural Chinese National Antarctic Research Expedition (CHINARE) in 1984, extensive surveys of the Southern Ocean have been conducted over the years. By utilizing national initiatives such as the “Chinese Pole Environment Comprehensive Investigation & Assessment Programmes” and the “Impact and Response of Antarctic Seas to Climate Change”, continuous and methodical research has been carried out on critical scientific matters concerning the development of the Southern Ocean ecosystem and its environmental components, leading to significant discoveries. This review article examines the Chinese research advancements related to the distribution of marine biogenic elements in the Southern Ocean and their ecological and environmental impacts. It primarily synthesizes research outcomes on the interrelationship between marine biogenic element cycling and planktonic ecosystems, the flux of biogenic material deposition and its seasonal variations, and sedimentary records of upper ocean processes. The ecological processes of Antarctic polynyas and their responses to global climate change are preliminaries discussed. Some suggestions are put forward for the future ecology and environment investigation in the Southern Ocean.

Dissolved oxygen (DO) and apparent oxygen utilization (AOU) are essential parameters for evaluating the impact of climate change on marine ecosystems. In this study, we utilized data on DO and AOU collected from the Amundsen Sea (western Antarctic) and the Cosmonaut Sea (eastern Antarctic) during the 38th Chinese National Antarctic Research Expedition, along with chlorophyll <em>a</em> (Chl <em>a</em>) data, to analyze the impact of primary production and the spatial distribution and structural features of water masses in these regions. The findings show that the standard deviation range of parallel DO samples is between 0.1 and 3.9 μmol·L⁻¹, meeting the precision criteria of the survey method. AOU values lower than 0.0 μmol·L⁻¹ were commonly observed in the surface waters of both regions, with the highest incidence in the polynya of Amundsen Sea, indicating a strong influence of high primary production. The Cosmonaut Sea exhibited the highest AOU values (higher than 160.0 μmol·L⁻¹) in the 75–500 m layer, while AOU value in the Amundsen Sea did not exceed 160.0 μmol·L⁻¹, suggesting potential upwelling of Circumpolar Deep Water to 100 m in the Cosmonaut Sea with minimal changes in its properties, whereas significant changes were noted in the properties of upwelling modified Circumpolar Deep Water in the Amundsen Sea. AOU values lower than 125.0 μmol·L⁻¹ were detected in the near-bottom waters of the Cosmonaut Sea, indicating the presence of Antarctic Bottom Water.

Virioplankton and picoplankton are the most abundant marine biological entities on earth and mediate biogeochemical cycles in the Southern Ocean. However, understanding of their distribution and relationships with environmental factors is lacking. Here, we report on their distribution and relationships with environmental factors at 48 stations from 112.5° to 150°W and 67° to 75.5°S in the Amundsen Sea of West Antarctica. The epipelagic stations were grouped into four clusters based on the virio- and picoplankton composition and abundance. Clusters three and four, which were associated with the ice-edge blooms in the coastal and Amundsen Sea Polynya (ASP) areas, had high abundances of autotrophic picoeukaryotes; this resulted in subsequent high abundances of heterotrophic prokaryotes and viruses. Cluster two stations were in open oceanic areas, where the abundances of autotrophic and heterotrophic picoplankton were low. Cluster one stations were located between the areas of blooms and the oceanic areas, which had a low abundance of heterotrophic prokaryotes and picoeukaryotes and a high abundance of virioplankton. The abundance of viruses was significantly correlated with the abundances of autotrophic picoeukaryotes and Chl-a concentration in oceanic areas, although this reflected a time-lag with autotrophic picoeukaryote and heterotrophic prokaryotes abundances in ice-edge bloom areas. The upwelling of Circumpolar Deep Water (CDW) might have induced the high abundance of autotrophic picoeukaryotes in the epipelagic zone, and the sinking particulate organic carbon (POC) might have induced the high abundance of heterotrophic prokaryotes and virioplankton in the meso- and bathypelagic zones. This study shows that the summer distribution of virio- and picoplankton in the Amundsen Sea of West Antarctica was mainly controlled by upwelling of the CDW and the timing of ice-edge blooms.

To understand the response of transparent exopolymer particles (TEP) to the changes in phytoplankton communities caused by melting sea ice, we collected samples from the polynya and open ocean affected by the Antarctic circumpolar current in the Amundsen Sea. TEP, pigments, and other environmental factors were analyzed. The results showed that high TEP content was mainly found in the polynya, and was higher in the surface layer than in the deep layer. The main factor that affected TEP distribution was the phytoplankton community. In the polynya area, the phytoplankton were dominated by low-iron Haptophyta. In the Antarctic circumpolar current region affected by ice-melting water, the dominant species was diatom type II. Our results revealed that low-iron Haptophyta may be the main contributors to TEP content.

Satellite remote sensing and numerical models are widely used to estimate large-scale variations in ocean carbon export, but the relationship between export efficiency (e-ratio) of sinking organic carbon out of the surface ocean and its drivers remains poorly understood, especially in the Southern Ocean. Here, we assess the effects of temperature and primary productivity on e-ratio by combining particulate organic carbon export flux from in situ measurements during 1997-2013, environmental parameters from satellite products, and outputs from ocean biogeochemical models in the Southern Ocean. Results show that "High Productivity Low E-ratio" (HPLE) is a common phenomenon in the Subantarctic Zone and the Polar Frontal Zone, but not the Antarctic Zone. The e-ratio shows little dependence on temperature below 6 °C. Our results support the hypothesis that the HPLE phenomenon is due to the large contribution of non-sinking organic carbon. Both temperature and ballast minerals play less important roles in controlling e-ratio than ecosystem structure at low temperatures. These findings suggest that non-sinking organic carbon, ecosystem structure, and region-specific parameterizations of e-ratio are key factors to quantify the carbon export in the Southern Ocean.