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. \n\nComparisons 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.

外来欧洲多毛类萨氏帚毛虫（Sabella spallanzanii）现已成为澳大利亚东南部潮下带生境中的优势类群。本研究探讨了萨氏帚毛虫对软沉积物大型底栖生物群落（macrofaunal assemblage）的物理影响。本研究在澳大利亚维多利亚州菲利普湾港贝拉林半岛克利夫顿斯普林斯的潮下带软沉积物中，针对萨氏帚毛虫的以下效应开展了测试：i）对现存大型底栖生物群落的影响；ii）对幼虫分布的影响；iii）对大型底栖生物定植过程的影响。

本数据集包含四种实验处理下各5个重复样方采集的软沉积物岩芯的大型底栖生物群落数据，四种实验处理分别为：① 真实帚毛虫组：从周边区域移植的15株萨氏帚毛虫个体组成的团块；② 模拟帚毛虫组：15个萨氏帚毛虫模拟物组成的团块；③ 对照组：未受扰动且无萨氏帚毛虫的沉积物；④ 扰动对照组：受扰动但无萨氏帚毛虫的沉积物。设置真实与模拟帚毛虫组样方，旨在验证：当存在萨氏帚毛虫时，大型底栖生物群落的变化是否仅由其物理作用引发。通过对比对照组与扰动对照组沉积物，可验证将萨氏帚毛虫移植至实验样方时产生的扰动，是否会导致大型底栖生物群落出现观测到的变化。

研究表明，真实帚毛虫组（RS）与模拟帚毛虫组（MS）、对照组（C）与扰动对照组（DC）之间，无论在单个分类单元还是组合类群层面均无显著差异。因此，本研究将RS组与MS组的数据合并，并与C组和DC组的合并数据开展对比分析。该分析结果显示：与无萨氏帚毛虫的沉积物相比，其存在可使猛水蚤目桡足类（harpacticoid copepods）、涟虫类（cumaceans）及介形类（ostracods）的丰度降低50%以上。上述三类分类单元合计占沉积物岩芯中总个体数的80%，因此萨氏帚毛虫的存在同样显著降低了沉积物中的总个体数量。