水生动物碳氮稳定同位素富集系数的整合分析

同位素富集系数即动物组织与其食物之间同位素丰度（δ）的差异值(Δ)，是稳定性同位素技术应用于生态系统营养关系、食性和食物网研究的重要参数.不同生境条件下和不同物种之间的富集系数通常被认为是相对稳定的，但越来越多的研究发现，富集系数在不同类型动物之间存在明显差异而不是一个恒定值，尽管这一差异范围仍不清楚.本文进行了3种不同权重设置方式的整合分析，综述并比较了4类水生动物(硬骨鱼类、甲壳类、爬行类、软体动物)的碳氮稳定同位素富集系数.在Web of Science和CNKI数据库上搜索2014年底之前发表的论文，获得了42篇包含140个Δ¹³C的研究结果和159个Δ¹⁵N的研究结果.使用3种不同的加权方式进行3次独立整合分析，3种加权方式分别是以方差倒数作为权重、以样本量作为权重和相等权重.结果表明，整合分析统计结果十分稳健，不同权重设置的分析结果差异很小.水生动物碳稳定同位素富集系数(Δ^13C)总体平均值为1.0‰，其中，硬骨鱼类1.0‰，甲壳类1.3‰，爬行类0.5‰，软体动物1.5‰；氮稳定同位素富集系数(Δ¹⁵N)总体平均值为2.6‰，其中，硬骨鱼类2.4‰，甲壳类3.6‰，爬行类1.0‰，软体动物2.5‰.统计分析表明，硬骨鱼类、甲壳类、爬行类、软体动物之间的Δ¹³C没有显著差异，而Δ¹⁵N存在显著差异.因此，应用稳定性同位素技术研究水生动物营养关系、食性和食物网中碳富集系数可以选择总体平均值，而氮富集系数则应根据不同水生动物类型选取相应的系数值.

Meta-analysis of stable carbon and nitrogen isotopic enrichment factors for aquatic animals.

Isotopic enrichment factor (Δ, the difference between the δ value of food and a consumer tissue) is an important parameter in using stable isotope analysis (SIA) to reconstruct diets, characterize trophic relationships, elucidate patterns of resource allocation, and construct food webs. Isotopic enrichment factor has been considered as a constancy value across a broad range of animals. However, recent studies showed that the isotopic enrichment factor differed among various types of animals although the magnitude of variation was not clear. Here, we conducted a meta analysis to synthesize and compare Δ^13C and Δ¹⁵N among four types of aquatic animals (teleosts, crustaceans, reptiles and molluscs). We searched for papers published before 2014 on Web of Science and CNKI using the key words “stable isotope or isotopic fractionation or fractionation factor or isotopic enrichment or trophic enrichment”. Forty two publications that contain 140 studies on Δ¹³C and 159 studies on Δ¹⁵N were obtained. We conducted three parallel meta analyses by using three types of weights (the reciprocal of variance as weights, the sample size as weights, and equal weights). The results showed that no significant difference in Δ¹³C among different animal types (teleosts 1.0‰, crustaceans 1.3‰, reptiles 0.5‰, and molluscs 1.5‰), while Δ¹⁵N values were significantly different (teleosts 2.4‰, crustaceans 3.6‰, reptiles 1.0‰ and molluscs 2.5‰).Our results suggested that the overall mean of Δ¹³C could be used as a general enrichment factor, but Δ¹⁵N should be chosen according to the type of aquatic animals in using SIA to analyze trophic relationships, patterns of resource allocation and food webs.