DGGE分析微型真核浮游生物遗传多样性及其与环境因子的相关性

应用变性梯度凝胶电泳(DGGE)技术对大庆红旗水库微型真核浮游生物的遗传多样性及其与环境因子的相关性进行研究。结果表明,大庆红旗水库的微型真核浮游生物群落具有丰富的多样性组成(检测到30个独立的OTU),且季节性变化显著。香农指数分析发现,夏季香农指数最高(平均值为2.58),秋季次之(平均值为2.17),春季最低(平均值为1.85)。各采样位点之间香农指数也存在差异,表现为沿岸带高于敞水带。UPGMA聚类分析发现,夏秋两季微型真核浮游生物的遗传多样性更为接近。遗传多样性与环境因子的CCA分析表明,温度、pH、总氮、叶绿素a浓度均与红旗水库微型真核浮游生物的遗传多样性有较高的关联度。

Distributions of Picophytoplankton and Phytoplankton Pigments Along a Salinity Gradient in the Changjiang River Estuary, China

We investigated the abundance of different picophytoplankton groups and the phytoplankton pigment ratio in relation to environmental factors such as nutrients and suspended solids along a salinity gradient in the Changjiang River Estuary.The average numbers of Synechococcus spp.（Syn） and picoeukaryotes （Euk） were （2.7 ±5.1）×l03 and （1.1±1.4）×l03 cells mL-1,respectively.Prochlorococcus spp.（Pro） was only found in the high-salinity brackish water with the concentration of 3.0× 10^3 cells mL-1.Syn and Euk numbers both tended to increase offshore and Syn showed a larger variation in cell abundance than Euk.The contribution of picophytoplankton to total phytoplankton biomass increased with increasing salinity and decreasing nutrient concentrations from the estuary to the open ocean.The response of different picophytoplankton groups to environmental variables was different.Water temperature was more important in its control over Euk than over Syn,while nutrients were more important in their influence over Syn than over Euk.Phytoplankton pigment ratios were different in the three different ecological zones along the salinity gradient （i.e.,freshwater zone with 0-5 range,fresh and saline water mixing zone with 5-20 range,and high-salinity brackish water zone with 20-32 range）,where three different phytoplankton communities were discovered,suggesting that phytoplankton pigment ratios can be considered as a complementary indicator of phytoplankton community structure in the Changjiang River Estuary.

Dynamic genetic features of eukaryotic plankton diversity in the Nakdong River estuary of Korea

Estuaries are environments where freshwater and seawater mix and they display various salinity profiles.The construction of river barrages and dams has rapidly changed these environments and has had a wide range of impacts on plankton communities.To understand the dynamics of such communities,researchers need accurate and rapid techniques for detecting plankton species.We evaluated the diversity of eukaryotic plankton over a salinity gradient by applying a metagenomics tool at the Nakdong River estuary in Korea.Environmental samples were collected on three dates during summer and autumn of 2011 at the Eulsukdo Bridge at the mouth of that river.Amplifying the 18 S rDNA allowed us to analyze 456 clones and 122 phylotypes.Metagenomic sequences revealed various taxonomic groups and cryptic genetic variations at the intra-and inter-specific levels.By analyzing the same station at each sampling date,we observed that the phylotypes presented a salinity-related pattern of diversity in assemblages.The variety of species within freshwater samples reflected the rapid environmental changes caused by freshwater inputs.Dinophyceae phylotypes accounted for the highest proportion of overall diversity in the seawater samples.Euryhaline diatoms and dinoflagellates were observed in the freshwater,brackish and seawater samples.The biological data for species composition demonstrate the transitional state between freshwater and seawater.Therefore,this metagenomics information can serve as a biological indicator for tracking changes in aquatic environments.