Primary consumers play a key role in coastal ecosystems by transferring organic matter from primary producers to predators. Among them, suspension-feeders, like bivalve molluscs are widely used in trophic web studies. The main goal of this study was to investigate variations of C and N elemental and isotopic ratios in common bivalves (M. edulis, M. galloprovincialis, and C. gigas) at large spatial (i.e. among three coastal regions) and different temporal (i.e. from seasonal to multi-decadal) scales in France, in order to identify potential general or specific patterns and speculate on their drivers.The observed spatial variability was related to the trophic status of the coastal regions (oligotrophic Mediterranean Sea versus meso- to eutrophic English Channel and Atlantic ocean), but not to ecosystem typology (estuaries, versus lagoons versus bays versus littoral systems). Furthermore, it highlighted local specificities in terms of the origin of the POM assimilated by bivalves (e.g., mainly continental POM vs. marine phytoplankton vs. microphytobenthic algae). Likewise, seasonal variability was related both to the reproduction cycle for C/N ratios of Mytilus spp. and to changes in trophic resources for δ¹³C of species located close to river mouth. Multi-decadal evolution exhibited shifts and trends for part of the 30-year series with decreases in δ¹³C and δ¹⁵N. Specifically, shifts appeared in the early 2000's, likely linking bivalve isotopic ratios to a cascade of processes affected by local drivers.

中文翻译：

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法国沿海地区以过滤器捕食的双壳类动物的碳，氮元素和同位素比率：对特定，地理，季节和多年代际变化的评估

主要消费者通过将有机物从主要生产者转移到捕食者而在沿海生态系统中发挥关键作用。其中，悬浮营养体，如双壳贝类软体动物，被广泛用于营养网研究。这项研究的主要目的是调查常见双壳类动物（M. edulis，M。galloprovincialis和C. gigas）中C和N元素和同位素比率的变化。）在法国的大空间（即三个沿海地区）和不同的时间（即从季节性到多年代）尺度上，以识别潜在的一般或特定模式并推测其驱动力。沿海地区的营养状况（地中海贫营养化，英吉利海峡和中营养富营养化的英吉利海峡和大西洋），而不是生态系统类型学（河口，泻湖，海湾，滨海和沿海系统）。此外，它强调了在被双壳类同化的POM起源方面的局部特异性（例如，主要是大陆性POM对海洋浮游植物对微底栖藻类）。同样，季节性变化与Mytilus的C / N比的繁殖周期有关。spp。并为δ营养资源的变化¹³靠近河口物种℃。多年代际变化表现出的变化和趋势，为30年系列减少的一部分δ ¹³ C和δ ¹⁵ N.具体而言，转变出现在2000年代初期的，可能连接双壳类同位素比值为受当地司机的过程级联。