Non‐traditional stable isotopes of metals were recently shown as new dietary tracers in terrestrial and marine mammals. Whether these metal stable isotopes can be used to understand feeding habits in stream food webs is not known yet. In this study, we explored the potential of stable isotopes of essential Mg (δ²⁶Mg) and Zn (δ⁶⁶Zn) as a new tool in stream ecology. For this purpose, we determined δ²⁶Mg and δ⁶⁶Zn values of stream organisms and their potential metal sources in upper and lower reaches of two streams in the Lake Biwa catchment, Central Japan. Our goals were (1) to explore variations in δ²⁶Mg and δ⁶⁶Zn across organisms of different feeding habits and (2) to understand Mg and Zn sources to stream organisms. Overall, δ²⁶Mg and δ⁶⁶Zn values of organisms were neither related to each other, nor to δ¹³C and δ¹⁵N values, indicating different elemental sources and factors controlling isotopic fractionation depending on element and taxa. Low δ²⁶Mg values in filter‐feeding caddisfly larvae and small gobies indicated aqueous Mg uptake. Higher δ²⁶Mg values in leaf‐shredding crane fly and grazing mayfly larvae suggested Mg isotopic fractionation during Mg uptake from the diet. While the δ²⁶Mg values of stonefly nymphs reflected those of caddisfly larvae as a potential prey, the highest δ²⁶Mg values found in dobsonfly nymphs can be explained by ²⁶Mg enrichment during maturing. δ⁶⁶Zn values of caddisfly and mayfly larvae indicated Zn was a mixture of aqueous and dietary available Zn, while higher δ⁶⁶Zn values in crane fly larvae pointed to Zn isotopic fractionation during Zn uptake from plant litter. δ⁶⁶Zn values in stonefly and dobsonfly nymphs were often in the range of those of caddisfly larvae as their prey, while dragonfly nymphs and small goby were depleted in ⁶⁶Zn relative to their dietary Zn sources. We conclude that δ²⁶Mg is a promising indicator to assess Mg sources in stream ecology depending on taxa, while the use of δ⁶⁶Zn is limited due to the complexity in Zn sources.

中文翻译：

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镁和锌稳定同位素作为了解流食网中镁和锌来源的新工具

金属的非传统稳定同位素最近在陆生和海洋哺乳动物中显示为新的饮食示踪剂。这些金属稳定同位素是否可用于了解流食网中的进食习惯尚不清楚。在这项研究中，我们探索了至关重要的镁（δ的稳定同位素的潜力²⁶ Mg）和锌（δ ⁶⁶锌）作为流生态学的新工具。为了这个目的，我们确定δ ²⁶ Mg和δ ^66个在琵琶湖集水区，中部日本两个流的上下游流生物及其潜在金属源的锌值。我们的目标是（1），探讨δ变化²⁶ Mg和δ ⁶⁶跨不同喂养习惯的生物体内的锌；（2）了解镁和锌的来源以使生物流化。总体而言，δ ²⁶ Mg和δ ⁶⁶生物体的锌值既不彼此相关，也不为δ ¹³ C和δ ^15个N个值，表示不同元素源和控制取决于元件和门类上同位素分馏因子。低δ ^26个在滤食性石蛾幼虫的Mg值和小虾虎鱼指示水性镁摄取。高δ ^26个在叶切碎鹤飞翔镁值和放牧蜉蝣幼虫从饮食中摄取镁在建议镁同位素分馏。虽然δ ²⁶StoneFly的若虫的毫克值反映了这些石蛾幼虫作为一个潜在的猎物，最高δ ^26个在若虫蛉发现毫克值可以通过进行说明²⁶毫克富集成熟期间。δ ⁶⁶个蛾和蜉蝣幼虫的锌值所指示的Zn是水性和膳食有效锌的混合物中，而较高的δ ^66个的Zn值在起重机蝇幼虫从植物垫料锌吸收过程中指出对于Zn同位素分馏。δ ^66个的Zn值StoneFly的和若虫蛉在这些石蛾幼虫作为其猎物的范围常常是，而蜻蜓若虫和小虾虎鱼在被耗尽⁶⁶的Zn相对于它们的膳食锌源。我们认为δ ²⁶Mg是评估流生态学中Mg来源的有前途的指标，取决于类群，而^δ66 Zn的使用由于锌源的复杂性而受到限制。