九龙江河口浮游植物的时空变动及主要影响因素

于2009年春（5月）、夏（8月）、秋（11月）在九龙江河口水域进行了水文、化学和生物的生态完全示范区综合外业调查，研究了九龙江河口浮游植物的种类组成、密度分布、季节变化、空间差异及主要影响因素，并结合前期资料分析了年际变动。结果表明，九龙江河口的浮游植物共记录7个门类75属134种。主体是硅藻，绿藻次之，甲藻和蓝藻较少，黄藻检出率高，裸藻和金藻零星检出。种类组成的空间差异大，绿藻在河口内区淡水水域比硅藻更占优势, 中肋骨条藻（Skeletonema costatum）、短角弯角藻（Eucampia zodiacus）、圆筛藻（Coscinodiscus spp.）、颗粒直链藻（Melosira granulata）、微小小环藻（Cyclotella. caspia）是河口区咸淡水水域及近海区的主要种类。浮球藻（Planktosphneria gelotinosa）、栅藻（Scenedesmus spp.）、盘星藻（Pediastrim spp.）、小席藻（Phormidium tenus）是河口内区淡水水域的主要种类。根据浮游植物的生态类型及其生境特征大致可分为三大类群。浮游植物密度夏季最高，平均为358.68103cells/L，密集中心的季节变化明显，密度分布由优势类群的密度分布决定。中肋骨条藻和短角弯角藻的数量庞大，导致优势种突出，多样性降低，种间分布不均匀，群落结构简单化。与史料比对，种类组成因淡水藻类的列入而更丰富，密度年际降低，中肋骨条藻仍是第一优势种，但优势度有较大降幅，优势类群有重大年际变化，细胞个体较小的种类占优。盐度和营养盐对浮游植物的分布及密度变化造成极大的时空差异，存在线性、复合线性、多项回归等复杂的相关关系。

Spatial and temporal variation of phytoplankton and impacting factors in Jiulongjiang Estuary of Xiamen, China

An comprehensive survey by hydrological, chemical and biological teams in the demonstration Eco- Securaty Zone of Jiulongjiang Estruary was conducted in Xiamen, China(24.3°-25.6° N, 117.7°-118.2° E) during spring(early May), summer(middle August)and autumn(late November)of 2009, aiming to support Eco-Security management of the estuary. This paper studied phytoplankton species composition, abundance, spatial distribution, community structure, seasonal and interannual variation due to the variations of environmental factors in fresh, brackish and sea waters. With analysis results of 97 samples taken from 21 stations in 3 seasons, it showed that there were 135 species of 7 phyla recorded. Diatom was the dominant species in abundance. Chlorophyceae was subdominant though it was dominant in freshwaters. Dinophyceae and Cyanophyceae were seldom observed and Euglenophyceae and Chrysophyceae even rarely in contrast to Xanthophyceae which was common in 3 seasons. Composition of phytoplankton species varied spatially. The phytoplankton, according to its ecotype and habitat can be grouped into freshwater, coastal and eurysalinity and oceanic species. The most important species in brackish and sea waters were Skeletonema costatum, Eucampia zodiacus, Coscinodiscus spp. Melosira granulate, Cyclotella caspia and etc.. The freshwaters were predominated by Planktosphneria gelotinosa, Scenedesmus spp., Pediastrum spp., Phormidium tenus and etc.. In contrast to a remarkable seasonal and spatial variation of species composition, the phytoplankton abundance changed less with stations horizontall though it varied with seasons. The abundance of phytoplankton ranged from (12.10-1135.21)×10³cells/L with means of 116.16×10³cells/L. Seasonal variation of abundance reached as high as 358.68×10³cells/L in summer, and to the lowest at 39.84×10³cells/L in autumn. It is evedent that distribution pattern and seasonal variation of phytoplankton abundance and was controlled by dominant species. Two areas with high abundance of phytoplankton can be discriminated at brackish wasters and sea waters in the Jiulongjiang Estuary, this 2 high phytoplankton abundance areas were supposedly caused by high nutrient input and interaction of interface generally. The Shannon-Wiener diversity indices and Pielou's evenness of phytoplankton community were low in brackish waters with sharp seasonal change. High abundance of Skeletonema costatum and Eucampia zodiacus were the cause of lower diversity, heterogeneous distribution and community simplification. Compared with historic dada composition of phytoplankton species became much diversified jointed by freshwater algae though abundance was lower than it used to be. Though the community were obviously dominated by small and chain forming species, such as Cyclotella caspia and Melosira granulate. It was Skeletonema costatum that remained the most dominant though the Mcnaughton index(Y)reduced sharply. The regression analysis showed that linear correlation, compound linear correlation and multi-regression were significant between phytoplankton abundance and salinity, SiO^-₄, NO^-₃ and PO^3-₄, respectively. Spatial and temporal variation of phytoplankton was associated mainly by salinity and nutrients in the three seasons of 2009. In conclusion, the phytoplankton community in the Jiulongjiang Estuary have made up an unique estuarine biota characteried by significant seasonal variation and hydrologic influence.