Dissertation Research: Effects of Omnivorous Fishes and Shrimps on Community Structure Along a Tropical Stream Continuum, Puerto Rico

9701299品客热带溪流的典型特征是丰富的杂食性鱼类和虾；然而，人们对这些宏观消费者在构建流社区中的相对角色知之甚少。这些物种通常有迁徙的生命周期，一生中既居住在低地，也居住在上游。从下游大量取水导致这些生物群直接死亡，并改变了它们的分布和丰度。拟议的研究将确定鱼类和虾对波多黎各东北部里约热内卢埃斯皮里图圣连续体的底栖生物群落结构的影响。本研究将解决以下问题：(1)杂食性鱼虾是否显著影响沉积物积累模式（即底栖沉积环境）？(2)排除杂食性鱼虾会发生营养级联吗？(3)鱼虾对河流连续体的影响是如何变化的？利用原位电封闭技术，在河流连续体的三个地点通过控制鱼虾对昆虫、藻类资源和沉积物积累的影响进行实验研究。建议的研究将提供关于杂食性动物在热带河流群落结构中的作用的信息，并将扩展我们之前关于鱼类和虾类对叶片分解的影响的研究，包括它们对河流连续体的初级生产者、沉积和群落结构的影响。这项研究还将提高我们预测这些受威胁的河流生态系统如何应对人为干扰的能力。

9701299 Pringle Tropical streams are typically characterized by an abundance of omnivorous fishes and shrimps; however little is known about the relative roles of these macroconsumers in structuring stream communities. These species typically have migratory life cycles, inhabiting both lowlands and headwaters during their lifetime. High levels of water withdrawal from lower stream reaches are resulting in direct mortality of these biota and changes in their distribution and abundance. Proposed research will determine the effects of fishes and shrimps on benthic community structure along the continuum of the Rio Espiritu Santo in northeastern Puerto Rico. In this study, the following questions will be addressed: (1) Do omnivorous fishes and shrimps significantly affect patterns of sediment accrual (i.e. the benthic depositional environment)?; (2) Do trophic cascades occur when omnivorous fishes and shrimps are excluded? and (3) How do effects of fishes and shrimps vary along the stream continuum? Effects of fishes and shrimps on insects, algal resources, and sediment accrual will be experimentally examined by manipulating their presence and absence at three sites along the river continuum using an in situ electric exclosure technique. Proposed research will provide information on the role of omnivory in structuring a tropical stream community and will expand our previous studies of effects of fishes and shrimps on leaf decomposition to include their effects on primary producers, sedimentation, and community structure along the river continuum. This research will also enhance our ability to predict how these threatened stream ecosystems respond to anthropogenic disturbance.