涠洲岛海域球形棕囊藻藻华过程中营养盐及浮游植物群落组成分析

Analysis of Nutrient and Phytoplankton Community during Phaeocystis globosa Bloom Near Weizhou Island, China

摘要:

球形棕囊藻(Phaeocystis globosa)是近年来北部湾常见的有害藻华原因种，涠洲岛海域作为广西沿海藻华的高发区之一，目前仍缺乏关于该海域球形棕囊藻藻华过程的相关研究。为探究涠洲岛海域球形棕囊藻藻华过程中营养盐的状况及藻华的发生对浮游植物群落组成的影响，对2017年3月下旬涠洲岛周边发生的球形棕囊藻藻华区域进行取样调查。结果表明，藻华期间水体中溶解有机磷含量与细胞及囊体密度呈显著正相关。本次藻华主要受水体中溶解态无机氮含量影响，多个调查站点的无机氮/无机磷(DIN/DIP)<10，且硅酸盐/无机氮(SiO₃^2–/DIN)>1，表明这些站点存在氮限制现象，而氮限制可能是本次藻华消亡的主要因素。调查区域共鉴定出浮游植物4门58种，球形棕囊藻细胞密度最高可达1.04×10⁸ cells/L，占浮游植物总细胞密度的98.28%。球形棕囊藻细胞密度与物种多样性指数存在显著的负相关关系。在营养缺乏条件下，有利于球形棕囊藻成囊的链状硅藻种类具有相对较大的细胞密度。

Abstract:

Phaeocystis globosa is a common harmful algal bloom species in the Beibu Gulf in recent years. As one of the areas with high frequency harmful algal blooms in Guangxi coast, there are seldom study on the P. globosa blooms in Weizhou Island. In order to investigate the status of nutrient and the effects of P. globosa blooms on phytoplankton community near Weizhou Island, a sampling survey was conducted on the area of P. globosa bloom occurred around Weizhou Island in late March 2017. The results showed that dissolved organic phosphorus (DOP) content had significantly positive correlation with the cell and colony density of P. globosa during the bloom. The bloom was mainly affected by the dissolved inorganic nitrogen (DIN), the ratio of DIN to dissolved inorganic phosphate (DIN/DIP) were lower than 10 in many stations, while the ratio of dissolved silicate to DIN (DSi/DIN) were higher than 1, indicated that nitrogen limitation existed in these areas. Nitrogen limitation was thought to be a major factor during the bloom’s demise. There were 58 species in 4 phyla of phyto- plankton identified in the survey area. The maximum abundance of P. globosa reached 1.04×10⁸ cells/L, accounted for 98.28% of total phytoplankton. There was a significantly negative correlation between the abundance of P. globosa and the species diversity index. In addition, under nutrient deficient condition, species of diatoms with chainlike structure which were beneficial to the formation of P. globosa colony had relatively greater abundance.