Understanding the mechanisms maintaining the biodiversity of plankton communities in marine ecosystems subject to a strongly variable ocean has become a critical issue for modern oceanography. Here, we used data on distribution of calanoid copepods in the upper layer of the ocean (0–500 m), a widely distributed taxonomic group in the pelagic realm, to assess the effects of changing oceanographic conditions on their diversity patterns and family and species richness. Copepods abundance and occurrence were evaluated from 2002 to 2015 covering the region extended between the coastal upwelling zone (CUP-Z) and the offshore region of Chile at subtropical and temperate areas. We used spatial analyses of community structure descriptors, such as abundance and diversity (family and species richness), multivariate analysis and General Additive Models (GAMS) in order to study the effect of surface temperature and its gradients, mixed layer depth, salinity and Chlorophyll-a on copepod diversity. Seventeen families were identified comprising 151 species distributed in 3 predefined zones in the onshore-offshore gradient covering the coastal upwelling, the coastal transition and the oligotrophic zones, whereas over the alongshore gradient, same families were majorly linked to the northern and southern portions of the sampled area (20–40°S). Families and species were significantly structured over the zonal gradient, revealing the dominant habitat for each of the families. Spatial patterns revealed the presence of transitional zones comprised by mixed taxa. Over the alongshore gradient this transition zone was linked to the subtropical convergence (30°S). The spatial variation of sea surface temperature (SST) revealed strong environmental zonation of temperature gradients across onshore-offshore and alongshore dimensions. Mean SST combined with mean mixed layer depth explained about 40% and about 29% of variation in family and species richness, respectively over the onshore-offshore axis. We thus conclude that the environmental zonation imposed by SST and its spatial gradients, considered as ecological barriers, is the key driver for maintaining diversity of copepods in the southeast Pacific.

中文翻译：

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东南太平洋海角类桡足类的环境梯度和空间格局

了解海洋生态系统中浮游生物群落生物多样性的维持机制已成为现代海洋学的一个关键问题。在这里，我们使用了海洋上层（0-500 m）中海鞘桡足类分布的数据，这是远洋领域广泛分布的分类群，以评估不断变化的海洋条件对其多样性模式和家庭和物种的影响丰富。从 2002 年到 2015 年评估了桡足类的丰度和发生率，覆盖了沿海上升流带 (CUP-Z) 和智利近海地区之间的亚热带和温带地区。我们使用了群落结构描述符的空间分析，例如丰度和多样性（家族和物种丰富度），多变量分析和通用加性模型 (GAMS) 以研究地表温度及其梯度、混合层深度、盐度和叶绿素 a 对桡足类多样性的影响。确定了 17 个科，包括 151 个物种，分布在陆上-近海梯度的 3 个预定区域，涵盖沿海上升流、沿海过渡区和贫营养区，而在沿海梯度上，相同的科主要与北岸和南岸有联系。采样区域 (20–40°S)。家庭和物种在带状梯度上有显着的结构，揭示了每个家庭的主要栖息地。空间模式显示存在由混合分类群组成的过渡区。在沿岸梯度上，这个过渡带与亚热带辐合（30°S）有关。海面温度 (SST) 的空间变化揭示了陆上-近海和沿海维度上温度梯度的强烈环境分带。平均海温与平均混合层深度相结合，分别解释了陆上-近海轴上约 40% 和约 29% 的科和物种丰富度变化。因此，我们得出结论，海温带来的环境分带及其空间梯度被视为生态障碍，是维持东南太平洋桡足类多样性的关键驱动因素。平均海温与平均混合层深度相结合，分别解释了陆上-近海轴上约 40% 和约 29% 的科和物种丰富度变化。因此，我们得出结论，海温带来的环境分带及其空间梯度被视为生态障碍，是维持东南太平洋桡足类多样性的关键驱动因素。平均海温与平均混合层深度相结合，分别解释了陆上-近海轴上约 40% 和约 29% 的科和物种丰富度变化。因此，我们得出结论，海温带来的环境分带及其空间梯度被视为生态障碍，是维持东南太平洋桡足类多样性的关键驱动因素。