Zooplankton monitoring in shelf seas predominantly uses nets that miss the benthic boundary layer (BBL) just above the seabed. However, this boundary between pelagic and benthic assemblages can be faunistically rich, having its own distinct hyperbenthic fauna and acting as a low-light refuge for overwintering or dielly migrating zooplankton. To compare species richness and composition between pelagic and BBL habitats, we sampled a long-term monitoring site in the Western English Channel seasonally. Metabarcoding methods applied to vertical net samples (top 50 m in a ∼54-m water column) and those from a hyperbenthic sledge generated >100 000 sequences clustered into 294 operational taxonomic units. Of these, 215 were found in the BBL and 170 in the water column. Some key taxa (e.g. mysids) were native to the BBL; by contrast, other delicate taxa (e.g. ctenophores) seemed to avoid the BBL. The major contrasts in plankton composition related to the seasonal cycle rather than to pelagic-BBL differences, suggesting that the basic dynamics of the site are captured by our ongoing long-term weekly resolution monitoring. Overall, metabarcoding approaches, applied to both water column and BBL, provide an independent view of plankton dynamics, and augment existing traditional methods.

中文翻译：

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水柱和底栖边界层之间分类学丰富度和组成的元条形码比较

在架子海中进行浮游动物监测的主要方式是使用那些错过海床上方底栖边界层（BBL）的网。但是，中上层和底栖组合之间的边界可能是丰富的，具有自己独特的高底栖动物群，并且是越冬或浮游动物浮游生物的避光所。为了比较中上层和BBL生境之间的物种丰富度和组成，我们季节性地在西英吉利海峡采样了一个长期监测站点。元条形码方法应用于垂直净样本（在约54 m水柱中排在前50 m）以及来自高底栖爬犁的样本，产生了超过10万个序列，这些序列聚集成294个操作分类单元。其中，在BBL中发现215个，在水柱中发现170个。一些主要的分类单元（例如，mysids）是BBL固有的。相比之下，其他精致的类群（例如，尾鳍类目）似乎避免了BBL。浮游生物组成的主要差异与季节周期有关，而不是与上层-BBL差异有关，这表明该地点的基本动态是由我们正在进行的长期每周分辨率监测所掌握的。总体而言，应用于水柱和BBL的元条形码方法提供了浮游生物动力学的独立视图，并扩展了现有的传统方法。