Knoff A J, Macko S A, Erwin R M
University of Virginia, Department of Environmental Sciences, Charlottesville 22903, USA.
Isotopes Environ Health Stud. 2001;37(1):67-88. doi: 10.1080/10256010108033282.
Food web studies often ignore details of temporal, spatial, and intrapopulation dietary variation in top-level consumers. In this study, intrapopulation dietary variation of a dominant carnivore, the Laughing Gull (Larus atricilla), was examined using carbon, nitrogen, and sulfur isotope analysis of gull tissues as well as their prey (fish, invertebrates, and insects) from the Virginia Coast Reserve estuarine system. As earlier traditional diet studies found evidence of individual dietary specialization within gull populations, this study used stable isotope analysis to assess specialization in a coastal Laughing Gull population. Specifically, blood, muscle, and feather isotope values indicated significant intrapopulation dietary specialization. Some gulls relied more heavily on estuarine prey (mean blood delta13C = -17.5, delta15N = 12.6, and delta34S = 9.3), whereas others appeared to consume more foods of marine origin (mean blood delta13C = -19.4, delta15N = 14.8, and delta34S = 10.4). It is important to account for such dietary variability when assessing trophic linkages in dynamic estuarine systems.
食物网研究常常忽略顶级消费者在时间、空间和种群内部饮食变化的细节。在本研究中，利用对笑鸥（Larus atricilla）及其猎物（鱼类、无脊椎动物和昆虫）的碳、氮和硫同位素分析，对弗吉尼亚海岸保护区河口系统中一种占主导地位的食肉动物——笑鸥的种群内部饮食变化进行了研究。正如早期传统饮食研究发现鸥类种群中存在个体饮食特化的证据一样，本研究使用稳定同位素分析来评估沿海笑鸥种群的特化情况。具体而言，血液、肌肉和羽毛的同位素值表明种群内部存在显著的饮食特化。一些笑鸥更依赖河口猎物（血液平均δ13C = -17.5，δ15N = 12.6，δ34S = 9.3），而其他笑鸥似乎食用更多海洋来源的食物（血液平均δ13C = -19.4，δ15N = 14.8，δ34S = 10.4）。在评估动态河口系统中的营养联系时，考虑这种饮食变异性很重要。
