夜光藻斑块分布与水环境因子的相关关系

Correlation Between the Patch Distribution of Noctiluca scintillans Bloom and Aquatic Environmental Factors

针对2016年4月珠江口广海湾和镇海湾暴发的夜光藻(Noctiluca scintillans)赤潮,分析了赤潮暴发海域水质状况和浮游植物群落组成的变化,探讨了夜光藻斑块状分布与水环境因子及浮游植物群落组成之间的相关关系。结果表明:调查海域营养状态(质量)指数均处于富营养化水平(E>1,NQI>3),且有毒污染指数、水质综合指数和有机污染指数处于轻度到中等污染等级。夜光藻的细胞密度介于0~29 444 inds·L^(-1)之间,且赤潮区硅藻和甲藻细胞密度显著增加,而绿藻、隐藻和蓝藻却显著降低,赤潮区、过渡区和非赤潮区平均微藻种类数为18,24和13。各调查站位水质因子聚类分析表明,河口区、港口码头区和水产养殖区均出现了夜光藻赤潮,其分布呈现出明显的斑块化特征;水质因子主成分分析表明,夜光藻赤潮改变了水质因子在主成分分组中的贡献率和相关系数;赤潮区水质因子的主成分旋转后载荷矩阵分布表明,第1主成分中主要反映了夜光藻大量生长导致的营养盐(氨氮、总氮、磷酸盐、总磷)的消耗及悬浮物、生化需氧量等的增加,第2主成分则反映了对重金属离子的选择性吸收。海水富营养化是夜光藻赤潮暴发的环境基础,且斑块化分布的夜光藻显著改变了局部海域海水中浮游生物群落结构和理化因子的组成。

Based on the data of Noctiluca scintillans bloom happened in the Guanghai Bay and Zhenhai Bay of the Pearl River Estuary in April 2016,the water quality and the change of the community composition of phytoplankton in the sea area under algal bloom were analyzed by using water quality evaluation,hierarchical cluster analysis and principal component analysis in order to establish a correlation between the patch distribution of N.scintillans bloom and the aquatic environmental factors.The results showed that the sea area under investigation was eutrophicated according to the trophic status index,and was slightly or moderately polluted based on the toxic substances of the sea water evaluated by the organic contamination index,the toxic pollution index and the comprehensive pollution index.The abundance of N.scintillans varied from 0 to 29 443.7 ind·L^-1 among the sampling stations,which indicated a notable patch distribution of the algal bloom.The composition of phytoplankton community was changed during the algal bloom.The average abundance of Bacillariophyta and Pyrrophyta increased evidently,while that of Chlorophyta,Cryptophyta and Cyanophyta decreased significantly in the algal bloom area.Moreover,the number of average species of the alga was 18,24 and 13 in the bloom area,the transition area and the non-bloom area,respectively.The dinoflagellate species,second to N.scintillans,were Akashiwo sanguinea and Ceratium furca,while the diatoms mainly included Dactyliosolen fragilissima,Guinardia flaccida（castracane） and Eucampia zoodiacus.Cluster analysis of the water quality factors revealed that N.scintillans bloom was detected in all the sampling stations in the river estuary,harbor area and aquaculture area where N.scintillans was distributed obviously in patches.The principal component analysis of water quality factors indicated that bloom of N.scintillans induced significant changes of the contribution rate and correlation coefficient of water quality factors.According to the rotated component matrix,the first principal component indicated the huge algal growth brought about consumption of nutrient（ammonia,total nitrogen,phosphate and total phosphorus） and increase of SS and CODMn,while the second principal component indicated the selected absorption of metals.Eutrophication of the sea water was the aquatic environmental basis of N.scintillans bloom.The patch distribution of N.scintillans changed obviously the structure of the phytoplankton community and the composition of the physical and chemical factors in the sea water of partial sea area.