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首页> 外文期刊>Estuarine Coastal and Shelf Science >Spatial And Seasonal Variations In The Ecological Characteristics Of The Free-living Nematode Assemblages In A Large Microtidal Estuary
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Spatial And Seasonal Variations In The Ecological Characteristics Of The Free-living Nematode Assemblages In A Large Microtidal Estuary

机译：大型微潮河口自由活动线虫组合生态特征的空间和季节变化

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This study has determined the ways in which the density, number of species, species composition and trophic structure of free-living nematode assemblages in the subtidal waters of a large southern hemisphere microtidal estuary change spatially and seasonally, and has explored whether those four biotic characteristics are related to certain environmental factors. Based on data derived from samples collected seasonally at 12 sites throughout the estuary, the densities and number of species of nematodes decreased progressively with distance from estuary mouth, to reach a minimum at sites where salinities were most variable, and then increased slightly in the uppermost part of the estuary where salinities were least. Densities were also generally greatest in spring, due largely to increases in the abundance of epistrate-grazing species at this time and thus when the amount of primary food (microphytobenthos) peaked. The spatial distribution of the composition of the nematode assemblages was closely correlated with salinity and, to a lesser extent, grain-size composition and amount of paniculate organic material (%POM) in the sediment Although species composition changed sequentially along the estuary, the change was particularly pronounced between sites above and below the area where salinities started to decline markedly and become more variable and %POM increased markedly. This reflected, in particular, far greater abundances of Spirinia parasitifera at the six downstream sites and of Theristus sp. 1 at the six sites further upstream. Species composition underwent pronounced seasonal cyclical changes at all sites, presumably reflecting interspecific differences in the timing of peak reproduction and thus of recruitment. The trophic structure of the nematode assemblages changed both spatially and temporally in relation to the relative abundance of different food sources. Thus, for example, non-selective deposit feeders, such as Theristus sp. l, dominated samples in the upper estuary, where %POM was by far the greatest, and was rare or absent at downstream sites. Conversely, epistrate grazers, such as species of the Chromadoridae, were most abundant at downstream sites in spring, when the density of the microphytobenthos reached its maximum.
机译：这项研究已经确定了南半球大型潮汐河口潮间带水下生活的线虫组合的密度，种类数量，种类组成和营养结构在空间和季节上变化的方式，并探讨了这四种生物特征与某些环境因素有关。根据在整个河口12个地点季节性采集的样本数据得出的结论，线虫的密度和种类随距河口的距离而逐渐减小，在盐度变化最大的地点达到最小，然后在最上端略有增加。盐度最低的河口部分。春季的密度通常也最大，这主要是由于此时以及当初级食物（微型底栖动物）数量达到顶峰时epi草放牧物种的丰度增加。线虫组合物的空间分布与盐度密切相关，在较小程度上与沉积物中的颗粒大小组成和颗粒状有机物质（％POM）的数量有关。尽管物种组成沿河口顺序变化，但变化在盐度开始显着下降并变得更加可变且％POM显着增加的区域上方和下方的站点之间尤其明显。特别是，这反映了六个下游位点的寄生寄生螺旋藻和Theristus sp。的丰度更高。 1个位于上游的六个站点。物种组成在所有地点都经历了明显的季节性周期性变化，大概反映了峰值繁殖时间以及因此而招募的种间差异。线虫组合的营养结构相对于不同食物来源的相对丰度在空间和时间上都发生了变化。因此，例如非选择性沉积物进料器，例如Theristus sp.。 l，在上河口占主导地位的样本中，％POM迄今为止最大，在下游站点很少或不存在。相反，春季的下游底栖放牧者（如Chromadoridae的物种）在微植物底栖动物的密度达到最大值时最丰富。

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