Estimating the trophic position of aquatic consumers in river food webs using stable nitrogen isotopes
Estimating the trophic position of aquatic consumers in river food webs using stable nitrogen isotopes
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DOI：
10.1899/0887-3593(2007)26
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发表时间：
2007-06-01
影响因子：
--
通讯作者：
Cabana, Gilbert
中科院分区：
文献类型：
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作者：
Anderson, Caroline;Cabana, Gilbert
各种消费者的营养位置的种内和种间变化是许多水生生态系统功能和动力学理论的核心。近年来，这些问题已经得到解决，使用稳定的N同位素（δ N-15），以估计消费者在水生生态系统中的营养地位。然而，人们需要校正的变化，在基线三角洲N-15之间的网站，以估计任何水生消费者的营养位置使用三角洲N-15。我们首先讨论了在河流生态系统中选择基线指标所需的步骤，其中丰富的食物网同位素数据已经公布，但有限的注意力已经支付给识别基线生物。我们检查了属于不同功能和分类群体的初级消费者中Delta N-15的地点内差异，发现Delta N-15存在显着差异。与其他初级消费者相比，收藏家的财富显著增加。我们建议刮刀作为基线Δ N-15指标，因为它们显示出较低的Δ N-15值，并且在整个研究地点比其他主要消费者分布更广。使用此基线Delta N-15，我们计算了87个河流食物网的消费者（无脊椎动物和小鱼）营养位置的连续估计。初级消费者有一个显着较低的平均营养位置（2.3）比捕食性无脊椎动物（2.9）和鱼类（3.5），这些结果是一致的估计传统的研究。然而，消费者（包括无脊椎动物和鱼类）的营养位置估计是高度可变的网站之间的标准偏差跨越高达0.67营养水平，这表明潜在的杂食性。将这些营养位置估计值与基于所有初级消费者的平均Δ N-15的估计值进行比较（没有将刮削器作为基线指标）表明，在估计基线Δ N-15时，使用有限数量的组和校正组间同位素差异，可以减少使用具有可变Δ N-15值的各种功能喂养组引起的一些偏差。
Intraspecific and interspecific variation in the trophic position of various consumers is central to many theories of aquatic ecosystem functioning and dynamics. In recent years, such issues have been addressed using stable N isotopes (delta N-15) to estimate trophic position of consumers in aquatic ecosystems. However, one needs to correct for variation in baseline delta N-15 among sites to estimate the trophic position of any aquatic consumer using delta N-15. We first discuss the steps needed to select a baseline indicator in river ecosystems, where abundant foodweb isotopic data have been published but limited attention has been paid to identification of baseline organisms. We examined within-site differences in delta N-15 among primary consumers belonging to different functional and taxonomic groups and found significant differences in delta N-15. Collectors were significantly enriched compared to other primary consumers. We propose scrapers as a baseline delta N-15 indicator because they showed low delta N-15 values and were more widely distributed than other primary consumers throughout our study sites. Using this baseline delta N-15, we calculated continuous estimates of trophic position of consumers (invertebrates and small fish) for our 87 river food webs. Primary consumers had a significantly lower mean trophic position (2.3) than predatory invertebrates (2.9) and fish (3.5), and these results are concordant with estimates based on traditional studies. However, trophic-position estimates of consumers (both invertebrates and fish) were highly variable across sites with standard deviations spanning up to 0.67 trophic levels, which suggested potential omnivory. Comparison of these trophic-position estimates with estimates based on mean delta N-15 of all primary consumers combined (no targeting of scrapers as baseline indicators) suggested that use of a constrained number of groups and corrections for isotopic differences among groups when estimating baseline delta N-15 could reduce some biases induced by the use of various functional feeding groups with variable delta N-15 values.