象山港春、夏季大中型浮游动物空间异质性

为探明象山港大中型浮游动物空间分布特征及主要影响因素,分别于2010年4月、7月大、小潮期对浮游动物群落和相关环境因子进行调查。四个航次共检出浮游动物成体14大类64种、浮游幼体10大类14种,春、夏季群落结构差异极显著(P=0.001),物种更替率为66.7%,优势种差异明显,共同优势种仅有短尾类溞状幼虫(Brachyura zoea)和仔鱼(Fish larvae)两类幼体;同一季节大、小潮物种相似度约为60%,群落结构差异较小(P=0.031);春季生物量和丰度高于夏季,但物种多样性低于夏季。温度是浮游动物群落季节变化的主导因素。方差分析、聚类和多维尺度分析显示:浮游动物群落空间异质性分布方式受潮流影响,群落结构在大潮期梯度分布特征明显,小潮期通常呈斑块性分布;生物量、丰度和多样性等参数的空间分布取决于群落的分布特征,并受影响于该参数在狭湾口内外的差异。典范对应分析及环境参数统计分析表明:梯度分布主要由盐度、悬浮物的梯度性特征决定;主导斑块性分布的因素多样,不同情况下可能为水深、叶绿素a、营养盐和内外水团相互作用;梯度性和斑块性分布均受到潮流影响。总体来看,象山港浮游动物空间分布主要受水文因素控制,受化学和生物因素影响较弱,其中叶绿素a浓度仅在春季与浮游动物丰度有一定相关性,溶解氧、酸碱度和营养盐等水质参数对浮游动物空间分布几乎无直接影响。

Spatial heterogeneity of macro- and meso-zooplankton in Xiangshan Bay in spring and summer

Spatial heterogeneity refers to non-uniformity and complexity of spatial distribution in ecological systems, and is generally regarded as the sum of patchy and gradient distribution patterns. The concept of spatial heterogeneity has long been applied to the field of ecology, but was introduced later in the marine environment because of the complexity caused by water fluidity and the weak motility of plankton. However, spatial heterogeneity of the marine environment is crucial to the diversity of structure and function of marine communities. Thus, spatial heterogeneity of plankton communities has been frequently discussed by marine ecologists. To investigate the spatial distribution of macro- and meso-zooplankton in Xiangshan Bay, the zooplankton community and associated environmental factors were investigated at neap and spring tide in April and July 2010. Using a shallow water type I plankton net, seventeen tows from the inner bay to the outer bay were conducted on each sampling occasion. Water quality parameters including: temperature, salinity, depth, pH, water clarity, dissolved oxygen, suspended solid concentrations and nutrient levels were also measured. A total of 64 adult zooplankton species representing fourteen taxa, and fourteen planktonic larval species from ten taxa were identified from the four cruises. Species composition changed 66.7% between spring and summer. While brachyuran zoea and larval fish were dominant in both seasons, other dominant species changed between the two seasons resulting in a significant difference (P = 0.001) in community structure. Species similarity between neap tide and spring tide was about 60% within the same season (P = 0.031). Biomass and abundance was higher in spring than in summer, while species diversity was lower. Temperature was the main factor which influenced seasonal variation in zooplankton. Analysis of variance, community clustering and non-metric multi-dimensional scaling analyses showed that the distribution framework of the zooplankton community was influenced by tide. Community structure exhibited a stronger gradient during spring tide, and was patchily distributed during neap tide. Community structure determined patterns of distribution, but this was influenced by differences in biomass, abundance and diversity inside and outside the mouth of Xiangshan Bay. Canonical correspondence analysis and regional analysis of environmental parameters showed that gradients in distribution were mainly determined by salinity and suspended solids. The main environmental parameters associated with patchiness included depth, chlorophyll a concentration, nutrients and the interaction of water masses in and out of Xiangshan Bay under different conditions. Gradient and patchiness patterns of zooplankton distribution were both influenced by the tide. The spatial distribution of zooplankton in Xiangshan Bay was strongly influenced by hydrological factors, and weakly influenced by chemical and biological factors. Zooplankton abundance and chlorophyll a concentration were correlated during spring. Water quality parameters including dissolved oxygen, pH and nutrient levels had little direct influence on the spatial distribution of zooplankton in the bay.