应用光合色素研究广西钦州湾丰水期浮游植物群落结构

通过2010年6月现场航次19个站点的调查,应用反相高效液相色谱(RP - HPLC) 并结合二极管阵列检测器分析技术,分析了丰水期广西钦州湾浮游植物光合色素组成,进而由CHEMTAX 软件估算全粒级浮游植物的群落结构。结果表明,钦州湾浮游植物光合色素含量以叶绿素a最高,其次为岩藻黄素；浮游植物的优势类群为硅藻,其次为蓝藻和青绿藻,它们分别平均占据了浮游植物生物量的70.2%、12.6%和9.4%,而其它藻类除了绿藻茅岭江河口占据较高的比例(40.2%)之外在其它站点所占比例很低。钦州湾浮游植物群落结构形成了茅岭江口、内湾、外湾和湾外近海共四种类型,茅岭江口以绿藻为优势类群,内湾以硅藻、蓝藻和青绿藻为主要优势类群,外湾以硅藻为单一优势类群,湾外相对于外湾硅藻比重略为下降。主要光合色素含量及浮游植物类群生物量的分布特征与盐度、营养盐关系密切,浮游植物群落结构的分布变化主要受径流及其输入导致的营养盐变化的影响,而这种影响导致了内湾和外湾之间浮游植物主要类群的生物量多寡及浮游植物群落结构的差异。

Phytoplankton community structure in Qinzhou Bay during flood season by analysis of HPLC photosynthetic pigment signatures

Based on a cruise in June, 2010 in Qinzhou Bay, structural characteristics of the phytoplankton community were studied during flood season. Phytoplankton samples from 19 stations were analyzed by RP-HPLC combined with DAD (diode array detector) to determine photosynthetic pigment composition in the study bay. Pigment data were converted into phytoplankton composition by software of CHEMTAX based on least squares method and the steepest descent algorithm. Our results showed that chlorophyll-a (Chl-a), fucoxanthin, chlorophyll-b (Chl-b) and zeaxanthin were the major pigments in Qinzhou Bay. Chl-a concentration ranged from 732 g/m3 to 9684 g/m3 (with a mean of 3574g/m3), and the concentration of fucoxanthin ranged from 51 g/m3 to 2714 g/m3 (with a mean of 917 g/m3). Mean concentrations of Chl-b and zeaxanthin were 161 g/m3 and 85 g/m3, respectively. Other pigments generally contributed a minor proportion of the total pigments, with average concentrations of less than 70 g/m3. Diatoms dominated in the phytoplankton community, contributing to 70.2% (mean value) of the phytoplankton biomass in QinZhou Bay, while the average percentage for cyanobacteria and prymnesiophyta was only 12.6% and 9.4%, respectively. Chlorophyceae was only abundant at the station in Maolingjiang estuary, which accounted for 40% of the phytoplankton biomass. The rest of the other phytoplankton were rare, and constituted <10% of all phytoplankton biomass. Diatom biomass ranged from 0.21g/L to 8.71 g/L (Chl-a biomass), and the distribution of diatom biomass was low in the inner bay and high in the outer bay. However, the biomass of cyanobacteria and prymnesiophyta in the inner bay was slightly higher than that in the outer bay. Phytoplankton communities in Qinzhou Bay were clustered into four types from the estuary to the outer bay, and were primarily influenced by floods on the Maolingjiang and Qinjiang rivers. Phytoplankton communities in the estuary were dominated by Chlorophyceae. Diatoms, cyanobacteria and prymnesiophyta were the major groups in the inner bay, while diatoms were dominant in the outer bay. Diatoms also dominated at the offshore stations; however, the proportion of diatoms decreased slightly with increasing distance from the coast. Additionally analysis also was carried out to illuminate the relationship between phytoplankton community structure and environmental factors in the study area. Results indicate that the distribution of major phytoplankton pigments and communities were coupled with environmental parameters in Qinzhou Bay. River flow, salinity and nutrients were the major controlling factors accounting for the spatial distribution and composition of phytoplankton in the bay.