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The impact of nonnative species and cultural eutrophication on the Lake Tahoe food web over time.

机译：随着时间的流逝，外来物种和文化富营养化对太浩湖食物网的影响。

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摘要

Aquatic ecosystems are impacted from anthropogenic stressors resulting primarily from increased nutrient loading and the introduction of non native species. In either case, these stressors may alter food web energetic pathways. This thesis evaluates the energetic consequences of cultural eutrophication and invasive species introductions on Lake Tahoe's food web. A novel approach comparing biotic stable isotope levels from preserved and contemporary specimens is utilized to measure impacts on food webs over time. In Chapter 1, the impact of 40 years of increased pelagic primary production on zoobenthos is measured. Increases in pelagic production shift the depth of 1% light penetration resulting in a decrease of periphyton production. As a result zoobenthic primary consumers receive a greater amount of their energy from newly sedimented pelagic primary production rather than from periphyton primary production. In Chapter 2, a retrospective analysis of over 120 years of species introductions and their impacts to the food web structure is quantified focusing on the differing impacts of vertebrate (lake trout) versus invertebrate (Mysis) introductions. Lake trout introductions did not result in significant food web structure changes however the elimination of the lake's only native predator (cutthroat trout) occurs. Mysis introduction result in a "middle out" effect shifting the trophic niche of chubs and lake trout by lowering their trophic position and shifting their energetic reliance on pelagic primary production. In Chapter 3, the impact Mysis introduction is evaluated on multiple levels of ecological organization (community and ecosystem). At the community level, Mysis eliminate their preferred cladoceran prey source. As a result they also reduce their reliance on herbivorous zooplankton over time and feed on algal-detrital material. On an ecosystem level Mysis may be playing an important role in controlling carbon export to the lake bottom by directly feeding on sedimented carbon.
机译：水生生态系统受到人为压力的影响，主要原因是养分含量增加和非本地物种的引入。无论哪种情况，这些压力源都可能改变食物网的能量通路。本论文评估了太浩湖食物网中的文化富营养化和入侵物种引进所产生的积极影响。一种比较保存的和现代标本中生物稳定同位素水平的新颖方法可用来衡量随时间推移对食物网的影响。在第1章中，测量了40年来中上层初级生产增加对底栖动物的影响。中上层产量的增加转移了1％的光穿透深度，从而导致水生植物减少。结果，游动底栖动物的初级消费者从新沉积的浮游鱼类初级生产中而不是浮游植物初级生产中获得了更多的能量。在第2章中，对超过120年的物种引进及其对食物网结构的影响进行了回顾性分析，重点是脊椎动物（湖鳟）与无脊椎动物（Mysis）引进的不同影响。引入鳟鱼并没有导致食物网结构的显着变化，但是消除了该湖唯一的本地捕食者（（鳟）。 Mysis的引入导致“中间”效应，即通过降低鲑鱼和湖鳟的营养位置并转移其对中上层初级生产的能量依赖，从而改变其营养价值。在第3章中，评估了Mysis引入对生态组织（社区和生态系统）的多个层次的影响。在社区级别，Mysis消除了他们偏爱的锁骨猎物来源。结果，随着时间的流逝，它们还减少了对草食性浮游植物的依赖，并以藻类碎屑为食。在生态系统层面，Mysis可能通过直接以沉积的碳为食，在控制向湖底的碳出口中发挥重要作用。

著录项

  • 作者

    Chandra, Sudeep.;

  • 作者单位

    University of California, Davis.;

  • 授予单位 University of California, Davis.;
  • 学科 Biology Ecology.; Biology Limnology.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 92 p.
  • 总页数 92
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生态学（生物生态学）;
  • 关键词

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