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Shipboard iron enrichment phytoplankton incubations were carried out in the Prydz Bay, Antarctic, in January through to March 2002. Waters for the three incubations ( Exp 1, 2 and 3 ) were collected from 20 m depth in three stations ( St. I -1, VII-1 and VII-5 ), respectively. Although the nutrient concentrations in the surface waters of the three stations were consistently high, the Chl a concentrations varied considerably. Chl a concentrations in the 20 m depth of St. I-1 and VII-1 werewas 2.35-2.65 for St. VII-5. There were six levels of enriched iron concentrations (control 5, 10, 20, 40 and 80 nM) in Exp 1 (6-29th, January) while three enriched iron levels (control 10 and 40 nM) were arranged in Exp 2 and 3 (both were from 20th February to 4 th March). The iron enrichments stimulated the phytoplankton growth and nutrient drawdown in Exp 1 and Exp 2. In Exp 3, phytoplankton growth and nutrient drawdown were at nearly the same rate in the control and iron enriched bottles. In Exp 1, Chl a concentrations in the bottles with 20, 40 and 80 nM iday, respectively, with a growth rate of 0.36-0.38 d-1. Chl a concentration in the day ( growth rate 0.27 d - 1 ). Phytoplankton growth rates in the control bottle and the bottle enriched with 5 nM iron were 0.13 and 0.16 d -1, respectively. In Exp 2, the Chl a growth rates were 0.13, 0.32 and 0.40 d-1 in the control bottle and bottles with 10 and 40 nM iron enrichments, respectively. It seems that 10 nM iron enrichment was not enough to stimulate the phytoplankton to reach their maximum growth rate. The result that the phytoplankton < 10 μm bloomed in Exp 1 and 2 was controversial to the "Ecumenical Iron Hypothesis" of Morel et al. ( 1991 ) that upon enrichment of iron, phytoplankton >10 μm would grow faster than phytoplankton<10 μm.
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Bacterial productivity was measured using 3H-thymidine methods in the Prydz Bay and its adjacent waters in the Southern Ocean during the 16th National Antarctic Research Expedition of China (CHINARE). The results showed that bacterial productivity in our study areas ranged from 4.5 to 191 ngC·dm -3·h-1. with an average of 50.4 ngC·dm-3·h-1 . These values were comparable to those reported for the Ross Sea. The mean ratio of bacterial productivity to primary productivity in our study areas was 41%. The general characteristics in the vertical profiles showed a subsurface maximum at most of the stations, which was also consistent with those observed in the other sea areas in the Southern Ocean. The spatial distribution of bacteri-al productivity and dissolved organic carbon in the surface waters showed that their variations were inversely correlative. The relationship among bacterial productivity, primary productivity and dissolved organic carbon suggested that bacterial productivity in the Prydz Bay and its adjacent water was influenced mostly by phytoplankton activities and the hydrologic conditions.
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In this paper, the spreading way in the southern hemisphere that anomalous warm water piled in tropical eastern Pacific is analysed and then impact of El Nino on the variability of the Antarctic sea ice extent is investigated by using a dataset from 1970 to 2002. The analysis result show that in El Nino event the anomalous warm water piled in tropical eastern Pacific is poleward propagation yet the westward propagation along southern equator current hasn 't been discovered. The poleward propagation time of the anomalous warm water is about 1 year or so. El Nino event has a close relationship with the sea ice extent in the Amundsen sea, Bellingshausen sea and Antarctic peninsula. After El Nino appears, there is a lag of two years that the sea ice in the Amundsen sea, Bellingshausea sea, especially in the Antarctic peninsula decreases obviously. The processes that El Nino has influence with Antarctic sea ice extent is the warm water piled in tropical eastern Pacific poleward propagation along off the coast of southern America and cause the anomalous temperature raise in near pole and then lead the sea ice in Amundsen sea, Bellingshausen sea and Antarctic peninsula to decrease where the obvious decrease of the sea ice since 80 'decade has close relation to the frequently appearance of El Nino.
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The abundance of general aerobic heterotrophic bacteria (GAB) from the water and sediment in the Bering Sea and the Chukchi Sea was determined by using petri dish cultivation and counting method. The abundance of GAB among the different sea areas, sampling sites, layers of sediments surveyed and adaptability to differential temperatures were studied. The result obtained showed that: the occurrence percentage of GAB in the surface water was higher than that in sediment, but the abundance was only 0.07% of sediment. The occurrence percentage of GAB in surficial layer of sediment was higher than that in the other layers. The occurrence percentage, abundance and its variation of GAB in Bering Sea were higher than that in the Chukchi Sea respectively. The average value of the abundance in the all sediment surveyed was 3166.3×102 CFU•g -1 (Wet.). The abundance of GAB in sediment showed a trend: roughly higher in the lower latitudinal area than higher latitude. The results from temperature test mean that: the majority of bacteria tested were cold adapted ones, minority might be mesophilic bacteria. The results indicated that, arctic ocean bacteria had a stronger adaptability to environmental temperature.
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The distributions and changes of dissolved organic carbon in the Prydz Bay and out open sea were investigated during CHIN ARE-15 (the 15th Chinese National Antarctic Research Expedition). The results showed that the content of DOC was higher in the Prydz Bay and outer open sea compared to those typical of surface oceanic levels (70-80 WV1), average content of DOC in the surface water was 102. 32 WM, the range was 68.23-125.92 WVI. The vertical distriljution of DOC in the water column was similar to many ocean sites, that is to say, the content of upper water is higher than deep water, a subsurface maximum persisted between 25-50 m. The DOC pool in the Prydz Bay were consisted with labile, semrlal) ile and refractory pools, in which refractory pools was mainly part. The concentration of refractory DOC was 92.34 and 76.89 WM in Prydz Bay and outer open sea, and account 77% and 82% for total DOC, respectively.
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The sea ice community plays an important role in the Arctic marine ecosystem. Species are transported by the Arctic transpolar drift system, and ice algae are an important source of the primary production that supports the sympagic community and may seed the spring phytoplankton bloom in ice edge areas. Because of the predicted environmental changes in the Arctic environment and specifically related to sea ice, the Arctic pack ice biota has received more attention in recent years using modern ice-breaking research vessels. Studies show that the Arctic pack ice contains a diverse biota and besides ice algae, the bacterial and protozoan biomasses can be high. Surprisingly high primary production values were observed in the pack ice of the central Arctic Ocean. Occasionally biomass maxima were discovered in the interior of the ice floes, a habitat that had been ignored in most Arctic studies. Light is one of the most important factors to control the biomass and structure of the pack ice community, together with other factors such as ice physical structure, temperature and brine volume.Many scientific questions, which deserve special attention, remained unsolved due to logistical limitations and the sea ice characteristics. Little is know about the pack ice community in the central Arctic Ocean. Almost no data exists from the pack ice zone for the winter season, although high biological activities were observed in winter pack ice in the Antarctic Ocean. Concerning the abundance of bacteria and protozoa, more studies are needed to understand the microbial network within the ice and its role in material and energy flows. The response of the sea ice biota to global change will impact the entire Arctic marine ecosystem and a long-term monitoring program is needed. The techniques, that are applied to study the sea ice biota and the sea ice ecology, should be improved.China has conducted some studies on Arctic pack ice ecology. The first Chinese Arctic expedition took place in summer 1999 and the second cruise is planned for the summer of 2003. Several ice stations were set up in the Canadian Basin where data are specifically scarce at present. The abundance, biomass and structure of community and the controlled environmental factors were investigated and grazing experiments were conducted.
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This paper consist of the following topics: (l) ignificance of observing lowet-latitude auroras. (2) Different kinds of atmospheric luminosity. (3) Chronological catalogues and map of isochasms for auroral visibility. (4) Analysis of archaea-auroras in low latitudes during earlier centuries. (5) A mora ob erving studies since International Geophysical Year (IGY). (6) Concerning prediction of auriora occurrence.
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