舟山海域夏、秋季浮游动物的分布特征及其与环境因子的关系

为更好地了解舟山海域浮游动物的群落结构、生物量和丰度的时空分布特征及其与主要环境因子的关系,分别于2014年7月和10月进行了夏季、秋季两次生态综合调查,并用多维尺度分析法、典范对应分析法对浮游动物群落结构进行了研究。结果表明:夏季舟山海域调查的浮游动物有13类,64种,优势种为背针胸刺水蚤(Centropages dorsispinatus)、圆唇角水蚤(Labidocera rotunda)、中华哲水蚤(Calanus sinicus)、精致真刺水蚤(Euchaeta concinna)、百陶带箭虫(Zonosagitta bedoti)和真刺唇角水蚤(Labidocera euchaeta);秋季鉴定到浮游动物12类,45种,优势种为背针胸刺水蚤(Centropages dorsispinatus)、百陶带箭虫(Zonosagitta bedoti)、双生水母(Diphyes chamissonis)、瓜水母(Beroёcucumis)和中华哲水蚤。夏季浮游动物平均丰度及平均生物量(144.0 ind/m3和176.3 mg/m~3)都分别高于秋季(21.4个/m3和86.3 mg/m3);Shannon-Wiener多样性指数夏季(3.03)高于秋季(2.82),Pielou均匀度指数则是秋季(0.83)高于夏季(0.64);夏季不同区域浮游动物群落之间具有明显的差异,而秋季大部分站位群落之间差异不显著;温度、盐度、叶绿素a浓度和营养盐含量是影响舟山海域浮游动物分布的主要环境因子;与历史资料相比,舟山海域浮游动物丰度及生物量呈下降趋势,其优势种保持较稳定。

Distribution of zooplankton in the Zhoushan Sea and its relationship with environmental factors in summer and autumn

The Zhoushan Sea (121.82°-122.35°E, 29.80°-30.22°N) is located along the northeast coast of Zhejiang Province, where the estuaries of the Yangze and Qiantang Rivers converge. The Zhoushan Sea is one of the deepest harbors in China, and it provides the largest marine economic base for the country. However, an increase in oil pollution and eutrophication in the area has been observed in recent years, which poses considerable threat to marine environments and resources. Understanding how oil pollution and eutrophication influence the marine ecological environment in the Zhoushan Sea is fundamental to protecting marine resources. Zooplankton plays a key role in marine food webs, and they are often used as indicator species of both small-, and large-scale nutrient pollution in aquatic ecosystems. However, there is little information available on how environmental factors influence the zooplankton community in the Zhoushan Sea.Our study investigated how environmental factors affect the zooplankton community in different seasons. In 2014, we conducted a summer (July) and autumn (October) survey in the Zhoushan Sea, to measure the abundance, biomass, and temporal and spatial distribution of the zooplankton community. Multidimensional scaling (MDS) and canonical correspondence analysis (CCA) were used to study the zooplankton community. In summer, we documented 64 species in 13 groups, with 6 dominant species: Centropages dorsispinatus, Labidocera rotunda, Calanus sinicus, Euchaeta concinna, Zonosagitta bedoti, and Labidocera euchaeta. In autumn, 45 species in 12 groups were identified, with 5 dominant species: Centropages dorsispinatus, Zonosagitta bedoti, Diphyes chamissionis, Beroë cucumis, and Calanus sinicus. The abundance and biomass of zooplankton were greater in summer (143.97 ind/m³ and 176.34 mg/m³,respectively) than in autumn (21.38 ind/m³ and 86.28 mg/m³,respectively). The Shannon-Wiener diversity index was higher in summer (3.03) than in autumn (2.82), and Pielou''s evenness index was lower in summer (0.64) than in autumn (0.83). Furthermore, according to our MDS analysis, zooplankton community composition was highly variable in summer, but not in autumn. The results of the CCA showed that temperature, salinity, chlorophyll a, and nutrients were the main environmental factors that affected the zooplankton community. Finally, we compared our results with historical data and found that zooplankton abundance and biomass has declined in the Zhoushan Sea, but the dominant species have remained relatively stable.