(Table 2) Concentration of phytoplankton pigments in Adventfjorden in spring and summer of 1997@en

The study was carried out from April 30 until July 13 of 1997 in Adventfjorden (Spitsbergen). Formation of a less saline and warmer surface water (~1 m thick) caused by melting of the ice was observed in the fjord during the first days of May. In summer the less saline surface layer was about 3 m thick. Euphotic depth measured under the ice sheet reached 12 m, whereas load of mineral matter brought with riverine discharge in summer (content of total particulate matter in the fjord reached 1.66 kg/m**2) dramatically reduced euphotic zone depth to 0.35 m. By pigment measurement three phases of phytoplankton development in Adventfjorden were distinguished: (1) spring bloom that has started under fast ice and reached maximum in the mid of May, (2) stagnation period in June, (3) increase of pigment concentration in July, what could indicate start of the next algae bloom. Analyses of chlorophylls and carotenoids revealed that diatoms (chl c, fucoxanthin), and green algae (chl b, lutein) dominated phytoplankton community in the fjord. Moreover, presence of peridinin indicates presence of Dinophyta and alloxanthin - occurence of Cryptophyta. In May and June 1997 phytoplankton appeared mainly in the surface of water, while in July, as a result of inflow of turbulent riverine waters into Adventfjorden, algae cells were pushed down and the highest numbers were observed at depth ~20 m. Great phaeopigments to chl a ratio (= 0.54) found in fjord seston in June and July probably shows strong impact of zooplankton grazing on phytoplankton development. High contribution of chlorophyllide a in porphyrin a poll in samples collected under fast ice (chlorophyllide a / chl a ratio = 0.18) reflects the final stage of algal communitie succession in ice, just before spring ice melt and release of biota to oceanic water. Chlorophyllide a content during summer was minor or not detectable, demonstrating that diatom cells were in good physiological condition. High chl a allomer / chl a ratio (average = 0.11 for the period investigated) confirms high oxygen concentration in environment of Adventfjorden.本研究于1997年4月30日至7月13日，在斯匹次卑尔根岛的Adventfjorden（阿德文特峡湾）开展。5月初，研究团队在该峡湾观测到海冰融化形成的低盐暖表层水，厚度约1米；夏季时，该低盐表层水层厚度约为3米。冰盖下测得的真光层（euphotic depth）可达12米，但夏季河流径流携带的矿物负荷（峡湾内总颗粒物含量达1.66 kg/m²）使真光层（euphotic zone）深度骤降至0.35米。通过色素检测，可将Adventfjorden内的浮游植物（phytoplankton）生长划分为三个阶段：(1) 春季水华：于固定冰下启动，5月中旬达到峰值；(2) 6月的停滞期；(3) 7月色素浓度回升，预示着新一轮藻类水华的启动。对叶绿素（chlorophyll）与类胡萝卜素（carotenoids）的分析显示，峡湾内的浮游植物群落以硅藻（diatoms，含叶绿素c、岩藻黄素（fucoxanthin））与绿藻（含叶绿素b、叶黄素（lutein））为主。此外，多甲藻素（peridinin）的检出表明甲藻门（Dinophyta）的存在，而别藻黄素（alloxanthin）则对应隐藻门（Cryptophyta）的出现。1997年5、6月，浮游植物主要分布于水体表层；7月时，因湍流型河流水体涌入Adventfjorden，藻类细胞被推至下层，最高丰度出现在约20米深度处。6、7月峡湾悬浮颗粒物中测得的脱镁色素（phaeopigments）与叶绿素a（chl a）比值高达0.54，这大概率反映了浮游动物（zooplankton）的摄食作用对浮游植物生长的强烈影响。在固定冰下采集的样本中，叶绿素酸酯a（chlorophyllide a）在卟啉a库中的占比较高（叶绿素酸酯a/叶绿素a比值为0.18），这反映了冰内藻类群落演替的末期阶段——即春季海冰融化、生物群落释放至海洋水体之前的阶段。夏季时叶绿素酸酯a的含量极低甚至无法检出，表明硅藻细胞的生理状态良好。叶绿素a异构体（chl a allomer）与叶绿素a的比值较高（研究期间平均值为0.11），证实了Adventfjorden环境中的高氧浓度。