Most tintinnid species have a shortest linear dimension < 50 μm. Hence, a priori, nets of mesh sizes ≥ 50 μm will likely under‐sample most tintinnid species. However, studies often appear (23 since 2015) using sampling with nets of meshes sizes ≥ 50 μm, reporting both tintinnid concentrations, and community composition. How biased are results from using coarse mesh nets? We provide a comparison of whole water vs. net sampling based on fortuitous, that is, unplanned, parallel sampling. Pairs of samples from a standard monitoring station in the Bay of Villefranche (N.W. Mediterranean Sea) taken on 44 dates from 2013 to 2018 were compared. Tintinnids were enumerated in settled material from a water column sample, an integration of six discrete depth samples between 5 and 70 m, prepared for analysis of phytoplankton composition and in material from a plankton net (52 μm mesh) tow from 70 to 0 m, taken the same day. Despite the large confidence limits due to low raw cell counts from whole water samples, cell concentration estimates were about an order of magnitude higher than those from plankton net samples and frequently biomass estimates as well. Community composition also differed. The most common species in whole water samples were small (diameter ≤ 20 μm), and some common forms were absent, or nearly, from the net samples. We show that, while valuable for collecting larger and rarer species, coarse net samples do not yield robust estimations of overall concentrations, nor allow identification of the dominant tintinnid species.

中文翻译：

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关于检查全水与浮游植物网（52μm筛网）样品之间的差异的注记，以表征丁香纤毛虫（海洋微浮游动物）的丰度和群落组成

最丁丁虫物种具有最短线性尺寸<50  μ米。因此，先验，网眼的网尺寸≥50  μ M将可能下采样最丁丁虫物种。然而，研究经常出现（23自2015年），使用与采样网格尺寸≥50的网 μm，同时报告丁丁腈浓度和社区组成。使用粗糙网格的结果有多偏颇？我们基于偶然的（即计划外的并行采样）提供了全水采样与净采样的比较。比较了2013年至2018年在44个日期从维勒弗兰奇湾（西北地中海）标准监测站采集的成对样本。在水柱样品的沉降材料中，在5至70 m之间的六个离散深度样品的积分，用于分析浮游植物成分的样品以及浮游生物网中的材料（  52μ米网距）从70到0 m，在同一天拍摄。尽管由于全水样品中的原始细胞计数低而使置信度限制很大，但细胞浓度估计值仍比浮游生物网样品中的细胞浓度估计值高约一个数量级，并且经常也对生物量进行估计。社区组成也有所不同。整个水样中的最常见的种类为小（直径≤20  μ M），和一些常用形式是不存在，或者几乎从净样品。我们显示，虽然对于收集更大和更稀有的物种很有价值，但粗糙的净样本无法对总体浓度产生可靠的估计，也无法识别主要的丁香物种。