一项新的研究报告说，在36条北美河流中的食物链（即由进食生物和被进食生物所进行的连续性的能量转移）受到了能量和水流变化的影响。
这些发现可能会影响河流中食物网的管理，因为干旱和气候变化预计会使河流变干加速并增加水流容积率的可变性；从而危及一个已经很脆弱的鱼类和其它水生生物的食物供应。 食物链的长度是决定能量流动、碳交换及营养物循环的生态系统的一个重要的特征。食物链长度还对人类的健康非常重要，它会影响我们所吃的动物体内污染物质的生物积累量。 然而，食物链的长度会有很大的变化，而生态学家一直在努力了解是什么造成了这些变化。John Sabo及其同事在此提出了不同因素（如生态系统的大小、能量供应及水流的容积率）的同时性效应是如何进行相互作用以影响食物链的长度的。
文章的作者观察了来自整个美国的36个流域的数据后发现，这些流域中的食物链长度会随着生态系统的变大而增加，随着能量流的变化而缩短（这与过去在河流中的发现是一致的）；但他们还显示了在生态系统大小与水流的容积率之间的关系会对食物链的长度造成很强的影响。 此外，河流的变干会缩短食物链的长度，因为断断续续的河流在水流的速度上要比长期持续性的河流或周期性河流有着高得多的变异性。（生物谷Bioon.com）
生物谷推荐英文摘要：
Science DOI: 10.1126/science.1196005
The Role of Discharge Variation in Scaling of Drainage Area and Food Chain Length in Rivers
John L. Sabo,1 Jacques. C. Finlay,2 Theodore Kennedy,3 David M. Post4
Food chain length (FCL) is a fundamental component of food web structure. Studies in a variety of ecosystems suggest that FCL is determined by energy supply, environmental stability, and/or ecosystem size, but the nature of the relationship between environmental stability and FCL, and the mechanism linking ecosystem size to FCL remain unclear. Here, we show that FCL increases with drainage area and decreases with hydrologic variability and intermittency across 36 North American rivers. Our analysis further suggests that hydrologic variability is the mechanism underlying the correlation between ecosystem size and FCL in rivers. Ecosystem size lengthens river food chains by integrating and attenuating discharge variation through stream networks, thereby enhancing environmental stability in larger river systems.
1 Faculty of Ecology Evolution and Environmental Sciences, School of Life Sciences, Arizona State University. P.O. Box 874501, Tempe AZ 85287–4501, USA.
2 Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, USA.
3 U.S. Geological Survey, Southwest Biological Science Center, 2255 North Gemini Drive, Flagstaff, AZ 86001, USA.
4 Department of Ecology and Evolutionary Biology, Yale University. P.O. Box 208106, 165 Prospect Street, New Haven, CT 06520–8106 USA.
