The coastal oceans can be highly variable, especially near ocean fronts. The Ushant Front is the dominant oceanographic feature in the Iroise Sea (NE Atlantic) during summer, separating warm stratified offshore waters from cool vertically-mixed nearshore waters. Mesozooplankton community structure was investigated over an annual cycle to examine relationships with oceanographic conditions. DNA metabarcoding of COI and 18S genes was used in communities from six sites along two cross-shelf transects. Taxonomic assignments of 380 and 296 OTUs (COI and 18S, respectively) identified 21 classes across 13 phyla. Meroplankton relative abundances peaked in spring and summer, particularly for polychaete and decapod larvae, respectively, corresponding to the reproductive periods of these taxa. Meroplankton was most affected by season, while holoplankton varied most by shelf position. Copepods with a mixed feeding strategy were associated with the most offshore sites, especially in the presence of the front, while filter-feeding or carnivorous copepods were associated with nearshore sites. In sum, mesozooplankton communities in well-mixed coastal waters were distinct from those found in the Ushant Front (high thermal stratification and chlorophyll-a). Furthermore, the benthic compartment, through its partial life cycle in the water column, contributed to high heterogeneity in planktonic communities over short temporal and spatial scales.

中文翻译：

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海洋结构和季节变化导致中型浮游生物在小空间尺度上的高度异质性

沿海海洋变化很大，尤其是靠近海洋前沿。Ushant 锋是夏季伊洛兹海（大西洋东北部）的主要海洋特征，将温暖的分层近海水域与凉爽的垂直混合近岸水域分开。每年对中型浮游生物群落结构进行调查，以检查与海洋条件的关系。COI 和 18S 基因的 DNA 元条形码被用于来自两个跨货架横断面的六个地点的群落。380 和 296 个 OTU（分别为 COI 和 18S）的分类分配确定了 13 个门的 21 个类别。浮游生物相对丰度在春季和夏季达到顶峰，特别是多毛类和十足类幼虫，分别对应于这些类群的繁殖期。浮游生物受季节影响最大，而全浮游生物因货架位置而变化最大。采用混合喂养策略的桡足类与大多数近海地点相关，尤其是在前线存在的情况下，而滤食性或食肉桡足类与近岸地点相关。总之，混合良好的沿海水域中的中型浮游生物群落与乌尚特前线（高热分层和叶绿素-a）中发现的那些不同。此外，底栖隔间通过其在水柱中的部分生命周期，在短期和空间尺度上促成了浮游群落的高度异质性。混合良好的沿海水域中的中型浮游生物群落与在 Ushant 前沿（高热分层和叶绿素-a）中发现的那些不同。此外，底栖隔间通过其在水柱中的部分生命周期，在短期和空间尺度上促成了浮游群落的高度异质性。混合良好的沿海水域中的中型浮游生物群落与在 Ushant 前沿（高热分层和叶绿素-a）中发现的那些不同。此外，底栖隔间通过其在水柱中的部分生命周期，在短期和空间尺度上促成了浮游群落的高度异质性。