Soft sediment assemblages at Casey Station: Spatial variation and human impacts. (core samples: Oct-Dec 1997)

A survey of macrobenthic assemblages in soft-sediments was done at Casey Station, East Antarctica. Samples were taken by divers using hand-held corers (core size - 10 cm diameter by 10 cm deep). The aims were: 1) To examine spatial variation at several scales in these assemblages; 2) To determine if there were differences between potentially impacted areas and control areas; 3) To determine the level of replication, taxonomic resolution and data transformation that are appropriate to studies of human impacts in Antarctic soft-sediment assemblages. Cores were collected by divers in a hierarchical, spatially nested design incorporating 4 scales: Locations (1000s of metres apart), Sites (100s of metres), Plots (10s of metres) and among replicates within plots (~1 metre). Four replicates for infaunal analysis were collected from each plot.Variation at the whole assemblage level was most significant at the largest scale: between Locations; but significant differences were also found between Plots within Sites, and between Sites within Locations. The impacted locations, near two waste tips, a sewage outfall and a wharf, as a group were significantly different to control locations. Impacted locations had less variable assemblages but more variable populations of dominant species than control locations. Control locations had greater richness and diversity than impacted locations. Patterns of assemblage structure were similar at fine (species and family) and medium (family to order) levels of taxonomic resolution but changed at coarse (phylum) levels of resolution. Assemblage patterns were similar between untransformed, square root and fourth root transformations but often different in presence/absence transformations.Concentrations of metals in sediments were also analysed and other environmental variables such as grain size and water depth were measured (two replicates from each plot). Multivariate correlations between the biological and environmental datasets were examined.Links to ASAC 1100.The fields in this dataset are:LocationSite/PlotReplicateAntimonyArsenicCadmiumChromiumCopperIronLeadManganeseMercuryNickelSilverTinZincWeightToxicity

本数据集针对南极东部凯西站（Casey Station）的软沉积物（soft-sediments）生境中大型底栖生物群落（macrobenthic assemblages）开展了调查研究。采样由潜水员采用手持取芯器（hand-held corers）完成，取芯规格为直径10厘米、深度10厘米。
本次调查的核心目标如下：1）探究此类群落在多个空间尺度下的分布变异特征；2）明确潜在受干扰区域与对照区域的群落差异；3）确定适用于南极软沉积底栖生物群落人类影响研究的适宜重复样本量、分类学分辨率（taxonomic resolution）及数据转换（data transformation）方法。
研究采用分层空间嵌套设计（hierarchical, spatially nested design），由潜水员采集岩芯样本，涵盖4个空间尺度：区域（Locations，间距达数千米）、样地（Sites，间距数百米）、样方（Plots，间距数十米）以及样方内的重复样本（间距约1米）。每个样方采集4份重复样本用于底内动物（infaunal）分析。
群落整体的空间变异在最大尺度（区域间）最为显著；同时在样地内的样方间以及区域内的样地间也检测到显著差异。两处垃圾倾倒点、一处排污口及一座码头附近的受干扰区域，其群落特征整体上与对照区域存在显著差异。受干扰区域的群落整体变异性更低，但优势物种种群的变异性高于对照区域；对照区域的物种丰富度与多样性均显著高于受干扰区域。
在精细分类尺度（物种与科级水平）及中等分类尺度（科级至目级水平）下，群落结构模式保持一致；但在粗分类尺度（门级水平）下，群落结构模式发生改变。未经数据转换、平方根转换及四次方根转换的数据集所呈现的群落模式较为相似，但采用出现-缺失转换（presence/absence transformation）的数据往往得到不同的群落模式。
研究同时测定了沉积物中的金属元素浓度，并同步记录了其他环境变量，如沉积物粒度（grain size）与水深（water depth，每个样方采集2份重复样本进行测定）。此外还分析了生物数据集与环境数据集之间的多元相关性（multivariate correlations）。
本数据集关联ASAC 1100。数据集包含以下字段：区域（Location）、样地/样方（Site/Plot）、重复样本（Replicate）、锑（Antimony）、砷（Arsenic）、镉（Cadmium）、铬（Chromium）、铜（Copper）、铁（Iron）、铅（Lead）、锰（Manganese）、汞（Mercury）、镍（Nickel）、银（Silver）、锡（Tin）、锌（Zinc）、重量（Weight）、毒性（Toxicity）