ABSTRACT: Gelatinous and soft-bodied zooplankton (GZ) have long been considered to have low energetic value (‘trophic dead end hypothesis’) and be insufficient to sustain higher trophic levels. However, the nutritional composition and energy content of GZ are often poorly known for entire groups, ignoring species-, size-, and stage-specific differences. In this study, organic matter and elemental composition (carbon and nitrogen) were measured for >1000 specimens from 34 GZ species collected from neritic and oceanic waters of the Northeast Pacific between 2014 and 2020. Species included 3 gastropods, 16 hydrozoans, 2 nude ctenophores, 6 scyphozoans, 3 tentaculate ctenophores, and 4 thaliaceans. Organic content and elemental composition were used to estimate energy content using published conversion factors and differed between and within taxonomic classes. Size-dependent variability was shown for several species. Differences in organic content and elemental composition by development stage were observed in a salp and scyphomedusa species, highlighting the need to consider life cycle stages separately. The relative energy values of GZ were generally low and highly variable, although some taxa were comparable to crustaceans. The findings of the present study emphasise the need for a more detailed consideration of GZ in marine food web models and time series analyses, to take into account their inter- and intraspecific variability.

中文翻译：

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东北太平洋的胶质和软质浮游动物：有机，元素和能量含量

摘要：长期以来，人们一直认为凝胶状和软体动物浮游动物（GZ）的能量值低（“营养死角假设”），不足以维持较高的营养水平。但是，对于整个群体，人们通常不了解GZ的营养成分和能量含量，而忽略了物种，大小和阶段的差异。在这项研究中，测量了2014年至2020年从东北太平洋的海域和海域采集的34个GZ物种中的1000多个标本中的有机物和元素组成（碳和氮）。物种包括3个腹足纲动物，16个水生动物，2个裸鳍足类动物。 ，6个鞘脂动物，3个带触角的触角藻和4个藻类。有机物含量和元素组成用于使用已公布的转换因子估算能量含量，并且在分类类之间和之内有所不同。显示了几种物种的大小依赖性变异性。在结节和水生美甲物种中，在发育阶段观察到有机物含量和元素组成的差异，这突出了需要单独考虑生命周期阶段的需要。GZ的相对能量值通常较低且变化很大，尽管某些分类单元可与甲壳类动物相提并论。本研究的发现强调需要在海洋食物网模型和时间序列分析中更详细地考虑GZ，以考虑其种间和种内变异性。在结节和水生美甲物种中，在发育阶段观察到有机物含量和元素组成的差异，这突出了需要单独考虑生命周期阶段的需要。GZ的相对能量值通常较低且变化很大，尽管某些分类单元可与甲壳类动物相提并论。本研究的结果强调，在海洋食物网模型和时间序列分析中需要对GZ进行更详细的考虑，以考虑其种间和种内变异性。在结节和水生美甲物种中，在发育阶段观察到有机物含量和元素组成的差异，这突出了需要单独考虑生命周期阶段的需要。GZ的相对能量值通常较低且变化很大，尽管某些分类单元可与甲壳类动物相提并论。本研究的结果强调，在海洋食物网模型和时间序列分析中需要对GZ进行更详细的考虑，以考虑其种间和种内变异性。