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Ecological distribution of recent deep-water foraminifera around New Zealand

机译:新西兰最近的深水有孔虫的生态分布

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摘要

Census counts (>63 μm) of 461 species in 361 samples are used as the basis for recognizing and mapping associations of deep-sea benthic foraminifera (50-5000-m depth) around New Zealand, southwest Pacific (28-60°S, 155°E-170° W). Fourteen faunal associations are identified by cluster analysis with five of these subdivided into 20 subassociations. The deepest associations, dominated by Nuttallides spp., Globo-cassidulina subglobosa, and diverse agglutinated species, occur at middle-lower abyssal depths (>3600 m) right around New Zealand, where they have been impacted by differing levels of taphonomic modifications. Two large associations are widespread throughout the region: one (Alabaminella weddellensis-Epistominella exigua) at lower bathyal-middle abyssal depths (~ 1500-4000 m) and the other (Cassidulina carinata-A. weddellensis-Abditodentrix pseudothalmanni) mostly at mid-bathyal-upper abyssal depths (~500-3000 m). Two deep-water associations occur on current-swept submarine highs: one (Trifarina angulosa-Ehrenbergina glabra) at lower bathyal-upper abyssal depths (1000-2400 m) along the southeastern margin of the Campbell and Bounty plateaux and the other (Bolivina robusta-Globocassidulina canalisuturata) at mid-upper bathyal depths in coarse sediment east and southeast of New Zealand. Two large associations occur at mid-shelf-uppermost-bathyal depths (50-400 m): one (Cassidulina carinata-Bulimina marginata-Gavelinopsis praegeri) around the coast beneath warm Subtropical Water and the other (C. carinata-T. angulosa-G. praegeri) further south beneath the cooler Subtropical Front and Subantarctic Water. A major reason for this study was to understand the environmental drivers of foraminiferal faunal distribution in this region to assist in paleoenvironmental interpretations of fossil faunas which have a significant regional character. Canonical correspondence analysis indicates that the distribution of bathyal and abyssal associations is more strongly influenced by depth-related variables, while shallower associations are influenced by latitude-related differences in surface-water characteristics. Environmental variables that influence faunal patterns at abyssal and bathyal depths appear to be, in decreasing order: food supply (organic-carbon flux, chlorophyll-a proxies), bottom-oxygen concentration, and carbonate corrosiveness (Fragmentation Index, planktic % proxies). Latitude-related variables driving mid-shelf-uppermost bathyal faunal patterns are water temperature, followed by primary productivity (phosphate and chlorophyll-a proxies). Environmental variables related to bottom-current strength appear to drive the faunal composition of three associations at shelf and bathyal depths. Cluster analysis enables the recognition of 22 anomalously deep faunas that are inferred to have a significant displaced content. There are no significant diversity trends correlated with depth, but species diversity decreases with increasing latitude at all depths.
机译:361个样本中461种物种的普查计数(> 63μm)被用作识别和绘制西南太平洋(28-60°S,新西兰)附近深海底栖有孔虫(深度为50-5000-m)的关联的基础155°E-170°W)。通过聚类分析确定了14个动物群落,其中5个亚群落被细分为20个亚群落。最深层的关联主要由Nuttallides spp。,Globo-cassidulina subglobosa和各种凝集物种组成,发生在新西兰附近的中下深渊深度(> 3600 m),在那里,它们受到不同水平的变态作用的影响。整个地区分布着两个大型的协会:一个(Alabaminella weddellensis-Epistominella exigua)在海底-深渊中部深度(约1500-4000 m),另一个(Cassidulina carinata-A。weddellensis-Abditodentrix pseudothalmanni)主要在南部-深渊上层深度(〜500-3000 m)。在当前扫描的海底高点上发生了两个深水关联:一个(Trifarina angulosa-Ehrenbergina glabra)在坎贝尔和邦蒂高原的东南边缘,沿深海底-上深渊深度(1000-2400 m),另一个(波利维纳·罗伯塔) -Globocassidulina canalisuturata)位于新西兰东部和东南部较粗的沉积物中的深基深处。在陆架中部至最上层的深海深度(50-400 m)发生了两个大的关联:一个在温暖的亚热带水之下的海岸附近(卡西琳娜carinata-Bulimina marginata-Gavelinopsis praegeri),另一个(C. carinata-T。angulosa- G. praegeri)在凉爽的亚热带锋面和亚南极水之下更南边。这项研究的主要原因是要了解该地区有孔虫动物区系分布的环境驱动因素,以协助对具有重要区域特征的化石动物区系进行古环境解释。典型的对应分析表明,深海相关的分布对海底和深海相联的分布影响更大,而浅水相关则受与纬度相关的地表水特征差异影响。影响深海和海底深度动物区系的环境变量以降序排列:食物供应(有机碳通量,叶绿素-a代理),底部氧气浓度和碳酸盐腐蚀性(碎片指数,板状%代理)。导致中层至上层海底动物区系分布的与纬度相关的变量是水温,其次是初级生产力(磷酸盐和叶绿素-a代理)。与底流强度有关的环境变量似乎驱动着架子和水深处的三个协会的动物组成。聚类分析可以识别22种异常深的动物群,这些动物群被推断具有明显的位移内容。没有与深度相关的明显多样性趋势,但是物种多样性在所有深度都随着纬度的增加而减小。

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