基于光合色素的钦州湾平水期浮游植物群落结构研究

Phytoplankton community structure based on pigment composition in Qinzhou bay during average water period

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2010年平水期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:平水期浮游植物特征光合色素含量以岩藻黄素最高,其次为叶绿素b、玉米黄素和青绿素,其它特征光合色素含量较低;水体中色素组成表明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73.9%、11.7%和8.7%,其它藻类所占比例很低。硅藻呈现出从湾顶往外随着盐度增加而增加的趋势,而青绿藻显现出相反的分布趋势。钦州湾浮游植物群落结构形成了茅岭江和钦江河口、湾颈-外湾近岸和外湾靠外海域共3种类型,平水期浮游植物群落结构的组成和分布特征主要是由茅岭江和钦江径流变化以及营养盐等环境所决定。平水期叶绿素b和青绿素在大部分站点存在证实了青绿藻在钦州湾的分布,而且表明青绿藻、绿藻和定鞭金藻等微型藻类在钦州湾占有相当比重,它们的重要性有待进一步研究。

Structural characteristics of phytoplankton community during normal season in 2010 in Qinzhou bay were studied. Phytoplankton samples were analyzed by RP-HPLC combined with DAD （diode array detector） to determine photosynthetic pigments composition in the study bay. Pigments data were converted into phytoplankton composition by software CHEMTAX based on least square method and steepest descent algorithm. Our results showed that salinity in the bay ranged from 14.2 to 31.0, and nitrate as well as phosphate concentrations decreased as salinity increasing from the top of bay to outer bay, which showed typical estuarial characteristics. Chlorophyll-a （Chl-a） , fucoxanthin, chlorophyll-b （Chl-b） , prasinoxanthin and zeaxanthin were the major pigments in the Qinzhou bay. Chl-a concentration ranged from 2693 μg/m3 to 4338 μg/m3 （with a mean of 3529 μg/m3）, and the concentration of fucoxanthin ranged from 390 μg/m3to 1081μg/m3（ with a mean of 629μg/m3）. Mean concentrations of Chl-b, prasinoxanthin and zeaxanthin were 304 μg/m3, 66μg/m3 and 65 μg,/m3, respectively. Other pigments generally contributed minor proportion of the total pigments, with average concentrations of less than 50 μg/m3. Diatoms dominated in the phytoplankton community, contributing to 76% （mean value ） of the phytoplankton biomass during normal season in the Qinzhou Bay, while the average percentage for prasinophyceae and cyanobacteria was only 12.2% and 5.5%, respectively. The rest of other phytoplankton was rare, which only took 〈10% of all phytoplankton biomass. Diatoms biomass ranged from 1.49 ×10^3 μg/m3 to 3.98 × 10^3 μg/m3 （ Chl-a biomass ）, and thedistribution of diatom biomass showed a pattern of low in the inner bay while high in the outer bay. However, the biomass of prasinophyceae showed a pattern of decreasing from the inner bay to the outer bay. Phytoplankton communities in the Qinzhou bay were clustered into three types from the estuary to the outer bay, which were primarily influenced by flood of the Maolingjiang River and Qinjiang River. Diatoms together with cyanobacteria and prasinophyceae were the major groups in the estuary of Maolingjiang River and the Qinjiang River, while diatoms were dominated between the inner bay and the outer bay. Diatoms also dominated in the offshore stations of the outer bay, and the proportion of diatoms increased a little and diatoms became a single dominated group. The distribution of major phytoplankton pigments and community were coupled with the environmental parameters in the Qinzhou Bay. River flow, salinity and nutrients were the major controlling factors accounting for the spatial distribution and composition of phytoplankton in the bay during the normal season.