Effects of Sabella spallanzanii physical structure on soft sediment macrofaunal assemblages: effects on existing assemblages

The introduced European polychaete Sabella spallanzani has become a dominant feature of sub-tidal habitats in south-eastern Australia. This study examines the physical effects of Sabella spallanzanii on macrofaunal assembleges of soft sediments. The effects of S. spallanzanii on: i) existing macrofaunal assemblege; ii) distribution of larvae and iii) colonisation of macrofauna were tested in sub-tidal soft sediments at Clifton Springs, Bellarine Peninsula, Port Phillip Bay, Victoria. This dataset gives the macrofauna assemblege of soft sediment cores collected from five replicate plots, in each of four experimental treatments: i) Real Sabella, a clump of 15 S. spallanzanii individuals transplanted from the surrounding region; ii) Mimic Sabella, a clump of 15 S. spallanzanii mimics; iii) Control, undisturbed sediment without S. spallanzanii and iv) Disturbed Control, disturbed sediments without S. spallanzanii. Plots containing real and mimic Sabella were used to test if changes in the assemblage of macrofauna in the presence of Sabella could be attributed to physical effects alone. A comparison of control and disturbed sediments was used to test if the disturbance created when transplanting Sabella into experimental plots contributed to any observed changes in the macrofauna assemblage.

Comparisons between Real (RS) and Mimic Sabella (MS), and Control (C) and Disturbed Control (DC) treatments were found not to differ significantly for any of the individual taxa or combined groups. Consequently, data from RS and MS treatments were pooled and compared against pooled data from C and DC treatments. This analysis found that the presence of Sabella reduced the abundance of harpacticoid copepods, cumaceans and ostracods by more than 50% compared with numbers found in sediment without Sabella. Collectively these taxa made up 80% of the total numbers of individuals in soil cores; as such the total number of individuals was also significantly reduced by the presence of Sabella.

本次研究的对象为已入侵澳大利亚东南部潮下带生境的欧洲引入种多毛类（polychaete）斯氏盘管虫（Sabella spallanzanii）。本研究旨在探究斯氏盘管虫对软沉积物大型底栖生物群落的物理影响。实验于维多利亚州菲利普湾贝拉林半岛的克利夫顿斯普林斯潮下带软沉积物中开展，检验了斯氏盘管虫对三方面的影响：① 现存大型底栖生物群落；② 幼虫分布；③ 大型底栖生物的定植过程。
本数据集收录了4组实验处理下，从5个重复样方中采集的软沉积物岩芯的大型底栖生物群落数据。4组实验处理分别为：① 真实盘管虫组：移植自周边区域的15株斯氏盘管虫聚群；② 模拟盘管虫组：15个斯氏盘管虫模型聚群；③ 对照组：无斯氏盘管虫的未扰动沉积物；④ 扰动对照组：无斯氏盘管虫的扰动沉积物。设置真实与模拟盘管虫组的目的，是检验大型底栖生物群落的变化是否仅由斯氏盘管虫的物理作用所导致；通过对比对照组与扰动对照组，则可验证移植盘管虫时产生的扰动是否会引发大型底栖生物群落的观测变化。
经检验，真实盘管虫组（RS）与模拟盘管虫组（MS）、对照组（C）与扰动对照组（DC）之间，在单个分类群及类群组合上均无显著差异。因此，本研究将RS组与MS组的数据合并，并与C组和DC组的合并数据进行对比。分析结果显示，相较于无斯氏盘管虫的沉积物，斯氏盘管虫的存在使猛水蚤目桡足类、涟虫目及介形类的丰度降低了50%以上。上述三类分类群的个体总数占沉积物岩芯总个体数的80%，因此斯氏盘管虫的存在同样显著降低了沉积物岩芯的总个体数。