Differential responses of aquatic consumers to variations in leaf-litter inputs
Differential responses of aquatic consumers to variations in leaf-litter inputs
复制标题
水生消费者对落叶投入变化的不同反应
作者：
Michael J. Rubbo;L. Belden;J. Kiesecker
水生食物网在陆地上的支持在生态学中已经得到了很好的证实。然而，虽然陆地能源补贴已被证明对水生食物网产生强烈影响，但尚不清楚这些补贴的变化（通过自然或人为因素）将如何影响接受国的生态系统。为了评估陆地补贴变化对水生食物网的影响，我们在人工池塘中控制了凋落叶的输入。减少凋落物输入对人工池塘中各响应变量均无影响。这可能是因为存在的最小陆地碳量与本地生产相结合足以维持食物网和/或食物网以实验设计未检测到的方式改变。然而，增加凋落叶的投入增加了林蛙幼虫的成活率和发育率。相反，增加凋落物输入似乎对浮游动物或蝾螈幼虫没有影响。增加凋落物投入也增加了人工池塘中溶解有机碳含量，降低了溶解氧饱和度。由于水生系统的系统呼吸通常由微生物呼吸主导，我们假设增加凋落物输入对林蛙的影响是蝌蚪食物资源（即微生物）增加的结果。蝾螈幼虫和浮游动物缺乏反应可能是由于在所有处理中为蝾螈提供足够食物的水箱中的浮游动物密度，特定浮游动物物种利用这些资源并将能量传递给蝾螈的能力存在差异，或者浮游动物的杂食性抵消了落叶输入的影响。需要进一步的工作来确定凋落物输入对该群落的浮游动物和蝾螈的影响。这些数据表明，凋落叶输入的变化可以影响食物网结构；然而，这些变化的重要性可能取决于不同消费者的营养状况。
Terrestrial support of aquatic food webs is becoming well established in the science of ecology. However, while terrestrial subsidies of energy have been shown to exert strong effects on aquatic food webs, it is less clear how variations in these subsidies, via natural or anthropogenic factors, will affect recipient ecosystems. To assess the influence of variations in terrestrial subsidies on an aquatic food web, we manipulated leaf-litter inputs in artificial ponds. Decreasing litter inputs did not affect any of the response variables in artificial ponds. This may be because the minimal amount of terrestrial carbon present combined with autochthonous production was enough to sustain the food web and/or the food web was altered in ways not detected by the experimental design. However, increasing leaf-litter inputs increased the percent survival and developmental rate of larval wood frogs (Rana sylvatica). Conversely, increasing litter input appeared to have no influence on zooplankton or salamander larvae. Increasing litter inputs also increased the dissolved organic carbon content and decreased the percent saturation of dissolved oxygen in artificial ponds. As system respiration in aquatic systems is frequently dominated by microbial respiration, we hypothesize that the effects of increasing litter input on wood frogs were the result of an increase food resources (i.e., microbes) for tadpoles. The lack of a response by salamander larvae and zooplankton may be due to the densities of zooplankton in tanks providing enough food for salamanders in all treatments, variation among specific zooplankton species in their ability to exploit these resources and transfer energy to salamanders, or omnivory among zooplankton offsetting the affects of leaf-litter inputs. Additional work is needed to determine the influence of litter inputs on zooplankton and salamanders in this community. These data demonstrate that variations in leaf-litter inputs can influence food web structure; however, the importance of these variations will likely be dependent upon the trophic position of various consumers.