桂山岛海域甲藻孢囊的分布与浮游植物休眠体萌发研究

为了了解珠江口桂山岛海域甲藻孢囊的分布及浮游植物休眠体的萌发状况,以揭示赤潮发生潜势,于2009年1月采集了珠江口桂山岛海域表层沉积物样品,对沉积物中甲藻孢囊的种类和数量进行分析,并对浮游植物休眠体进行了萌发试验。结果表明,桂山岛海域甲藻孢囊有21种,原多甲藻类孢囊在种类数上占优势。甲藻孢囊密度较低,为110~315个/g,平均为202个/g,养殖区密度高于非养殖区。异养型甲藻孢囊百分比含量较高,表明了该海域较高的富营养化程度。活体孢囊密度百分比达61.8%,说明表层沉积物中存在大量未萌发的活性孢囊,为赤潮暴发埋下了隐患。萌发的浮游植物种类数较少,为19属22种。20 d和40 d萌发的浮游植物细胞平均密度分别为490个/g和264个/g。萌发的甲藻优势种为Biecheleriopsis adriatica,其次为锥状斯氏藻(Scrippsiella trochoidea);萌发的硅藻主要以中肋骨条藻(Skeletonema costatum)、旋链角毛藻(Chaetoceros curvistus)和舟形藻(Navicula sp.)占优势。桂山岛海域有毒有害甲藻孢囊的广泛分布以及潜在赤潮种类的大量萌发,表明该海域有较高的赤潮发生风险。

Distribution of dinocysts and the germination of phytoplankton resting spores in surface sediments from the Guishan Island sea area in the Pearl River Estuary of the South China Sea

In order to understand the distribution of dinocysts and the potential of harmful algal blooms (HABs) found in the Guishan Island sea area in the Pearl River Estuary, dinocysts were analyzed in surface sediment samples, collected in January 2009. The surface sediments were incubated for 20, and 40 days, and germinated vegetative cells were examined; a total of 21 types of dinocysts were observed, with Protoperidinium species cysts found to be the most abundant and diversified. The average concentration of germinated phytoplankton was 490, and 264 cells/g, respectively, after 20 and 40 days incubation. Cyst concentrations were low, ranging from 110 to 315 cysts/g, with an average of 202 cysts·g^-1, while higher concentrations of cysts were found in stations located in aquaculture areas. The proportions of cysts from heterotrophic dinoflagellates were higher, indicating a high nutrient level in this sea area. Furthermore, proportions of living cysts averaged 61.75%, indicating the high potential for HABs. The species diversity of germinated phytoplankton recorded was low, and altogether 22 taxa within 19 genuses were observed. Interestingly, a woloszynskioid species, Biecheleriopsis adriatica, was predominant in the germinated dinoflagellates analyzed, with Scrippsiella trochoidea found to be the next dominant dinoflagellate. In the germinated phytoplankton samples, Skeletonema costatum, Chaetoceros curvisetus, and Navicula sp. were the dominant diatoms. The results from this study suggest the high risk of HABs in the Guishan Island sea area, as indicated by the wide distribution of cysts of HAB species, and the massive germination of potential HAB species.