ABSTRACT: Bacterioplankton and protists fulfil key roles in marine ecosystems. Understanding the abundance and distribution of these organisms through space and time is a central focus of biological oceanographers. The role of oceanographic features, in addition to environmental conditions, in structuring bacterioplankton and protist communities has been increasingly recognised. We investigated patterns in bacterioplankton and protist diversity and community structure across the Southland Front system, a compaction of the subtropical front zone, to the east of New Zealand’s South Island. We collected 24 seawater samples across a ~65 km transect and characterised bacterioplankton and protist community composition using high-throughput sequencing of the 16S and 18S rRNA genes, respectively. We identified frontal waters as a bacterioplankton diversity hotspot relative to neighbouring subtropical and subantarctic waters, but did not find evidence of this effect in protists. Bacterioplankton showed pronounced spatial structuring across the front, with communities closely tracking water type through the region. Protist communities also tracked water type through the region, though this effect was substantially less pronounced. We used an ecological null model approach to demonstrate that protist communities are primarily assembled through stochastic processes, whilst bacterioplankton are primarily assembled through deterministic processes across the Southland Front system. We suggest that this divergence emerges from fundamental differences in the characteristics of bacterioplankton and protist communities. Our findings add to a growing body of literature highlighting the importance of oceanographic features in shaping bacterioplankton and protist communities, promoting the necessity for such features to be considered more explicitly in the future.

中文翻译：

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不同的过程在整个海洋前沿构成了浮游生物和原生生物群落

摘要：浮游细菌和原生生物在海洋生态系统中发挥关键作用。通过空间和时间了解这些生物的丰度和分布是生物海洋学家的中心重点。除了环境条件外，海洋学特征在构造浮游生物和原生生物群落中的作用已得到越来越多的认识。我们调查了新西兰南岛以东的南大陆锋系统（亚热带锋区的压实）中浮游细菌和原生生物多样性以及群落结构的模式。我们在一个约65 km的横断面收集了24个海水样本，并分别使用16S和18S rRNA基因的高通量测序对了浮游细菌和原生生物群落组成进行了表征。我们确定额叶水是相对于邻近的亚热带和亚南极水域的浮游细菌多样性热点，但没有在原生生物中发现这种作用的证据。浮游细菌在前部表现出明显的空间结构，社区密切跟踪整个区域的水类型。尽管该影响明显不那么明显，但自卫社区也追踪了整个区域的水类型。我们使用生态零模型方法来证明，原生生物群落主要是通过随机过程组装的，而浮游细菌则主要是通过整个南国前线系统的确定性过程组装的。我们建议这种差异是由浮游生物和原生生物群落的特征的根本差异引起的。