In benthic ecosystems, organic matter (OM), prokaryotes, and meiofauna represent a functional bottleneck in the energy transfer towards higher trophic levels and all respond to a variety of natural and anthropogenic disturbances. The relationships between OM and the different components of benthic communities are influenced by multiple environmental variables, which can vary across different habitats. However, analyses of these relationships have mostly been conducted by considering the different habitats separately, even though freshwater, transitional, and marine ecosystems, physically linked to each other, are not worlds apart. Here, we investigated the quantity and nutritional quality of sedimentary OM, along with the prokaryotic and meiofauna abundance, biomass, and biodiversity, in two sampling periods, corresponding to high vs. low freshwater inputs to the sea, along a river-to-sea transect. The highest values of sedimentary organic loads and their nutritional quality, prokaryotic and meiofaunal abundance, and biomass were consistently observed in lagoon systems. Differences in the prokaryotic Operational Taxonomic Units (OTUs) and meiofaunal taxonomic composition, rather than changes in the richness of taxa, were observed among the three habitats and, in each habitat, between sampling periods. Such differences were driven by either physical or trophic variables, though with differences between seasons. Overall, our results indicate that the apparent positive relationship between sedimentary OM, prokaryote and meiofaunal abundance, and biomass across the river-lagoon-sea transect under scrutiny is more the result of a pattern of specifically adapted prokaryotic and meiofaunal communities to different habitats, rather than an actually positive ‘response’ to OM enrichment. We conclude that the synoptic analysis of prokaryotes and meiofauna can provide useful information on the relative effect of organic enrichment and environmental settings across gradients of environmental continuums, including rivers, lagoons, and marine coastal ecosystems.

中文翻译：

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沿河-泻湖-海洋梯度的沉积有机质，原核生物和鱼卵

在底栖生态系统中，有机质（OM），原核生物和藻类动物是向更高营养级转移能量的功能性瓶颈，它们都对各种自然和人为干扰做出响应。OM与底栖生物不同组成部分之间的关​​系受到多种环境变量的影响，这些变量在不同的生境中可能会有所不同。然而，尽管彼此之间物理联系并不紧密的淡水，过渡和海洋生态系统，对这些关系的分析大多是通过分别考虑不同的栖息地来进行的。在这里，我们调查了两个采样期内沉积物OM的数量和营养质量，以及原核生物和中部动物的丰度，生物量和生物多样性，分别对应于高和低。沿河海横断面向海洋的淡水输入量低。在泻湖系统中始终观察到最高的沉积有机负荷值及其营养质量，原核生物和藻类的丰度以及生物量。在三个生境之间以及在每个生境中，在采样期间之间，观察到原核生物分类单位（OTUs）和气代植物分类组成的差异，而不是分类单元丰富度的变化。尽管季节之间存在差异，但这种差异是由物理变量或营养变量驱动的。总体而言，我们的结果表明，沉积物OM，原核生物和藻类丰度之间存在明显的正相关关系，受到审查的整个泻湖-海相横断面的生物量更多是由于原核和半动植物群落专门适应不同生境的模式产生的结果，而不是对OM富集的实际“反应”。我们得出的结论是，原核生物和鱼类的概要分析可以提供关于跨河流，泻湖和海洋沿海生态系统等环境连续体梯度的有机富集和环境设置的相对影响的有用信息。