珠三角河网水域栅藻的时空分布特征

珠三角河网水域是珠江之水流入南海的必经之地,对2012年该水域浮游植物群落中的栅藻种类丰富度和生物量的时空特征及其环境影响因子进行系统阐析。调查期间共发现栅藻24种(包括变种、变型),其中具刺和无刺种类分别为11种和13种。出现率高且生物量贡献率大的物种仅3种,包括被甲栅藻原变种(Scenedesmus armatus var.armatus)、被甲栅藻博格变种双尾变型(S.armatus var.boglariensis f.bicaudatus)和二形栅藻(S.dimorphus),分析认为这3个物种在栅藻种群中的生态优势很可能与其形态特征存在一定的关联。栅藻种类丰富度的季节分布呈现丰水期高于枯水期的特征,空间分布呈现河网中部站位低于外侧站位的特征。此外,种类丰富度的空间分布格局存在季节差异,丰水季节呈现河网中部站位明显低于外侧站位的特征,而枯水季节西江沿线站位种类丰富度明显偏低。分析认为,水温和径流是影响栅藻种类丰富度季节变动的关键因素;同时,径流也是影响总种类丰富度空间分布格局的关键因素,而水温和营养盐是影响不同季节种类丰富度的空间格局的重要因素。栅藻种群生物量的季节分布呈现丰水期高于枯水期的特征,空间分布表现为珠江桥站位的生物量明显高于其它站位。分析认为,径流和水温是决定种群生物量季节变动的关键因素,而营养盐、水体稳定性和盐度是决定生物量空间分布格局的关键因素。栅藻生物量与种类丰富度的关系基本符合单峰模型,且偏重于单峰模型的上升区,丰富了全球多样性模式的分级特征和区域特征。

Temporal and spatial pattern of Scenedesmus in the river web of the Pearl River Delta, China

The Pearl River Delta (PRD) in Guangdong province is one of the most economically prosperous areas in China. A large number of domestic and industrial wastes are produced together with the economic development and 10% of waste output in growth rate has been estimated in the past few years. The complicated river web of the delta, which is characterized as criss-cross and multiple river channels, is the essential entrance for the Pearl River water entering into the South China Sea. Many studies have been focusing on physical and chemical factors of this region, but few referred to aquatic organisms, especially in recent years. To understand the temporal and spatial distribution pattern of Scenedesmus, a common green algal group of riverine phytoplankton community, seasonal investigation has been carried out in the river web area in 2012. The thirteen representative sampling sites settled covered almost the whole area and shaped in umbrella-type. The coherence between the biomass of each taxa and environmental factors was also analyzed using PCA method to evaluate the key factors for explaining the interaction mechanisms. Also, the regional characteristics of phytoplankton biodiversity pattern were evaluated from the genus level based on the results.During the investigation, the total 24 taxonomic species (including variant and derivative) were identified, including 11 taxa with spines and 13 taxa none. Although several species showed high occurrence rate, their contribution to total phytoplankton biomass was low, and less than 1% in terms of averages. However, relative abundance between different taxa was closely related to their occurrence rate. Three species (S. armatus var. armatus, S. armatus var. boglariensis f. bicaudatus, S. dimorphus) showed relatively high values in both occurrence and biomass, which was assumed related to their special morphological features. Seasonal variation pattern of both species richness and biomass indicated high in wet seasons and low in dry seasons, water temperature and discharge have been found to be responsible for this through the PCA analysis. Water temperature mainly influenced the growth and physiological conditions of Scenedesmus, while discharge mainly determined the exterior supplement of the algae. The spatial distribution pattern of total species richness showed high in outside stations and low in central stations, but this pattern had apparent seasonal differences. The patterns of May and August were in accordance with that of the total, and the patterns of March and December just showed high values in sampling sites close to Guangzhou. Through the PCA analysis, discharge, water temperature and nutrients have been found to be the key factors to influence this spatial pattern. The spatial distribution pattern of biomass showed extremely higher in ZJQ than those in other stations. Nutrients, water stability and salinity have been found to be the key factors for the spatial pattern through the PCA analysis. In addition, the relationship between Scenedesmus biomass and species richness was analyzed, and it was in consistent with the global phytoplankton biodiversity pattern, and had an incline to ascending part of the model, which also promotes the grading and regional understanding of the global diversity pattern.