楚科奇海和白令海网采浮游植物群聚的多元分析

根据1999年夏季(7~8月)我国首次北极科学考察期间“雪龙”号考察船在楚科奇海(66°0.3'~75°18.6' N, 153°36.5'~174°59.5' W)和白令海(55°59.8'~66°0.3' N,173°21.1' E~175°53.9' W)49个站采集的样品研究了该区网采浮游植物的分布特征。结果显示,两个调查区的浮游植物多样性指数和均匀度平均值几乎相等且都较低,分别变动在1.88~1.90和0.43~0.45之间。然而,两个区存在明显的空间异质性。就丰富度和种类组成而言,楚科奇海的细胞密度和物种总数量远高于白令海,前者为9 122.56×10⁴ cells·m^-3 和103种,而后者为161.78×10⁴ cells·m^-3和71种。上述生态学指标不同站点间的变异也大。用多元分析方法对浮游植物群聚的分布异质性加以讨论。主成分分析(PCA)结果表明,解析调查区浮游植物分布方差的33.0%的两个最主要成分(即主要物种变量)分别是北极-北方浅海群落(泛北极群落)和北方大洋群落的主要种群。前者包括某些圆心硅藻,如旋链角毛藻 (Chaetoceros curvisetus)、柔弱角毛藻(C. debilis)、聚生角毛藻(C. socialis)、叉尖角毛藻(C.furcellatus)等多种寡色体类角毛藻以及冷淡劳德藻 (Lauderia glacialis)、丹麦细柱藻 (Leptocylindrus danicus)、诺登海链藻(Thalassiosira nordenskioldii)和脆杆链藻(Bacteriosira fragilis)等;后者主要有小环毛藻 (Corethron criophilum)、平截鼻状藻 (Proboscia truncata)、无刺鼻状藻 (P. inermis)、西氏细齿状藻(Dentecula seminae)和一些多色暗角毛类角毛藻,如大西洋角毛藻(Chaetoceros atlanticus)等。泛北极群落主要分布于楚科奇海南部和中部,而北方大洋群落的主要分布区在白令海调查区的西南部。通过聚类分析还辨认出7个包含不同群落的主要网采浮游植物分布区,但是由于不同水系的不同程度影响,以及极具不确定性的浮冰的位置及其物理状态(聚集、开裂和消融等)也会在短时间内给调查区生物过程导入变异性,从而使得这些分布区的归类复杂化,尤其在楚科奇海。

A MULTIVARIATE ANALYSIS OF NETPHYTOPLANKTON ASSEMBLAGES IN THE CHUKCHI SEA AND BERING SEA

Background and Aims The phytoplankton in the Arctic seas is rarely explored on a large geographic scale, particularly at the community level.The diversity, density and distribution variability of netphytoplankton assemblages were measured at 49 stations in the Chukchi Sea (66°0.3´-75°18.6´ N, 153°36.5´-174°59.5´ W) and Bering Sea (55°59.8´-66° 0.3´ N, 173°21.1´-175°53.9´ W) during the FCNARE (1999) cruise on the Xuelong Research Vessel of SOA, China.  Methods The diversity indices combining the data on the abundance within a species in a community into a single number were adopted to understand the state of the community. Principal component analysis (PCA) of data was applied for examing the distribution variability of netphytoplankton. Cluster analysis was used as indicative of the degree of similarity in species composition among stations to the selected species having a frequency of occurrence greater than 10% of the total samples. Key Results Both the mean index values of phytoplankton diversity and evenness were approximately equally low at the two study areas, ranging from 1.88 to 1 .90 and from 0.43 to 0.45, respectively. However,both the average cell density and total species numbers in the Chukchi Sea were far greater than these in the Bering Sea, reaching 9 122.56×104 cells?m-3 and 103 taxa in the Chukchi Sea but only 161.78×104 cells?m-3 and 71 taxa in the Bering Sea. The results of PCA indicated that the first two components (the most important species variables) explained 33.0% of the total variance in the netphytoplankton distribution in the study areas. The main populations belong to the arctic_boreal community (pan_arctic community) and boreal oceanic community, including some centric diatoms in the arctic_ boreal community, such as Chaetoceros curvisetus, C.debilis, C.socialis, C.furcellatus etc. belonging to the Chaetoceros_Oligochromatophorusgroup, and Lauderia glacialis, Leptocylindrus danicus, Thalassiosira nordenskioldii and Bacteriosira fragilis etc., as well as Corethron criophilum, Proboscia truncata, P. inermis, Dentecula seminaeandsomeand some species belonging to Chaetoceros_Phaeoceros_Polychromatophorus group such as Chaetoceros atla nticus etc. in the boreal oceanic community. Seven major netphytoplankton regions containing different phytoplankton communities in two study areas were distinguished by the cluster analysis. However, the extremely dynamic physical nature of the drifting packice (e.g. packing, breaking up and melting) introduce short_term variability into the water conditions that no doubt affect the species composition; hence, the groupings of the netphytoplankton in the different regions may reflect temporal conditions, particularly in the Chukchi Sea, that require repeated sampling in order to better classify the regions. Conclusions There were strong differences in the density and taxa of the netphytoplankton between the Chukchi Sea and Bering Sea. The density and composition were highly variable among sampling sites, particularly in Chukchi Sea.