Use of allochthonous resources by zooplankton in reservoirs
Use of allochthonous resources by zooplankton in reservoirs
复制标题
水库浮游动物对外地资源的利用
作者：
K. A. Emery;G. Wilkinson;Flannery G. Ballard;M. Pace
水生食物网由系统内的初级生产（原生体）以及系统外产生并运输到系统内的有机物质（异原生体）支持。浮游动物利用外来资源，特别是在高陆地负荷和中低内部初级生产的系统中。我们假设，由于高陆地负荷和残留的水下陆地物质，浮游动物对所有水库的异源资源的利用将是显著的，并将随着水库年龄梯度的增加而下降。利用氢稳定同位素和贝叶斯混合模型，估算了10个水库外来源对有机质库和甲壳类浮游动物生物量的贡献。所有体系中溶解有机质（DOM）均以异源源为主（后分布中位数为92%），而颗粒有机质（POM）组成各不相同（2-68%为异源），且在老储层中异源含量较低。浮游动物异质性与水库年龄没有关系。在不同的生态系统中，甲壳类浮游动物的异食率从26%到94%不等，在4个水库中测量到的潮藻异食率也有类似的变化（33-94%）。在一些水库中，消费异质高于POM异质，可能是由于陆地DOM途径很重要和/或藻类资源不可食用（例如蓝藻）。与许多湖泊一样，在我们研究的水库中，外来输入占基础消费者有机质的很大一部分。
Aquatic food webs are supported by primary production from within the system (autochthony) as well as organic matter produced outside of and transported into the system (allochthony). Zooplankton use allochthonous resources, especially in systems with high terrestrial loading and moderate to low internal primary production. We hypothesized that due to high terrestrial loads and remnant submerged terrestrial material, allochthonous resource use by zooplankton would be significant in all reservoirs and would decline along an increasing reservoir age gradient. Using hydrogen stable isotopes and a Bayesian mixing model, we estimated the contribution of allochthonous sources to organic matter pools and crustaceous zooplankton biomass for ten reservoirs. Dissolved organic matter (DOM) in all systems was dominated by allochthonous sources (posterior distribution median >92% allochthonous), while particulate organic matter (POM) composition varied (2–68% allochthonous) and had a lower allochthonous fraction in older reservoirs. There was no relationship between zooplankton allochthony and reservoir age. Crustaceous zooplankton allochthony varied among systems from 26 to 94%, and Chaoborus allochthony, measured in four reservoirs, was similarly variable (33–94%). Consumer allochthony was higher than POM allochthony in some reservoirs, potentially due to terrestrial DOM pathways being important and/or algal resources being inedible (e.g., cyanobacteria). As with many lakes, in the reservoirs we studied, allochthonous inputs account for a significant fraction of the organic matter of basal consumers.