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The effects of reduced stream flow caused by natural and anthropogenic disturbances on headwater stream food webs: Evidence from stable isotope analysis.

机译：自然和人为干扰引起的水流量减少对上游水源食物网的影响：稳定同位素分析的证据。

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摘要

A combination of stable isotope ratios, gut content analyses, and known feeding habits of macroinvertebrates was used to determine the impacts of natural and anthropogenic alterations to flow in headwater stream systems in southwestern Ontario. Specifically, this study looked at the effects of beaver impoundment and the effects of water abstraction on food webs in headwater streams. Analyses of food webs determined the impacts of reduced flow on the food webs, and elucidated specific changes in food webs from reference to impacted sites.;In a second study, water abstraction caused changes to the invertebrate food webs as evidenced through stable isotope analysis (SIA). Although food web complexity was not changed, impacted sites consistently had smaller food web areas as seen through food web polygons, and a higher overall niche occupancy than reference sites. Reduced current velocity by water abstraction allowed detritus to accumulate which provided an ample food supply to invertebrates and represented the area of highest carbon flow in the food web, allowed for more specific predation, and promoted growth of aufwuchs that was also an important food source for invertebrates thereby creating a smaller food web area and higher niche occupancy.;The food webs did not conform to the universally accepted trophic enrichment factors of 0.4‰ for delta13C and 3.4‰ for delta 15N. Instead, omnivory was generally accepted as the preferred feeding method, meaning that consumer delta13C signatures had to be intermediate between two or three food sources. For delta15N, it was found that trophic enrichment was in the range of 2.0-2.5‰ and food webs were constructed based on this premise.;Voucher taxa from feeding guilds should not be used to exemplify the feeding habit, diet, or trophic status of the guild. Individuals within guilds have unique signatures, and do not always rely on the same food source. Each constituent of the food web needs to be analyzed separately in order to fully understand the feeding links, interactions and carbon flow within the food web.;Impoundment by beaver significantly affected the delta13 and delta 15N signatures of macroinvertebrates, and increased the abundance of species suited to a more lentic environment. Carbon and nitrogen stable isotope analyses (SIA) were used to demonstrate and interpret differences between species above and below a beaver impoundment in a cold water headwater stream in southwestern Ontario. The delta13C and delta 15N signatures did not vary with season or year within each reach, but food web polygons indicated carbon signatures were depleted and nitrogen signatures were enriched downstream of the impoundment relative to reaches above the impoundment. The lack of canopy cover in the beaver impounded reach facilitated increased autochthonous growth, which in turn caused increased invertebrate biomass and food web complexity. Increased sedimentation and uptake by aquatic plants when combined with high sunlight irradiance promoted a fast-growing environment that caused less discrimination against delta 15N, resulting in an overall enrichment of delta15N in the beaver impounded area.
机译：稳定同位素比，肠道含量分析和已知的大型无脊椎动物摄食习惯的组合，用于确定自然和人为改变对安大略省西南部上游水流系统流量的影响。具体而言，这项研究着眼于海狸蓄水的影响和取水对上游水源食物网的影响。对食物网的分析确定了流量减少对食物网的影响，并阐明了从参考到受影响地点的食物网的具体变化。;在第二项研究中，通过稳定的同位素分析证明，取水导致无脊椎动物食物网发生了变化（新航）。尽管食物网的复杂性没有改变，但从食物网多边形的角度来看，受影响的站点始终具有较小的食物网区域，并且与参考站点相比，整体利基占有率更高。通过取水降低流速，碎屑会积聚，这为无脊椎动物提供了充足的食物供应，并代表了食物网中碳流量最高的区域，允许进行更具体的捕食，并促进了uf夫的生长，uf夫也是重要的食物来源无脊椎动物因此产生较小的食物网面积和较高的生态位占有率。食物网不符合公认的营养富集因子，δ13C为0.4‰，δ15N为3.4‰。取而代之的是，杂食被普遍接受为首选的喂养方式，这意味着消费者的delta13C签名必须介于两种或三种食物来源之间。对于delta15N，发现营养富集范围在2.0-2.5‰之间，并在此前提下构建了食物网。;不应使用来自行会的凭证类目来举例说明食饵的习性，饮食或营养状况公会。行会中的个人具有独特的签名，并不总是依靠相同的食物来源。食物链的每个组成部分都需要单独分析，以充分了解食物链内的饲养联系，相互作用和碳流量。；海狸的积水显着影响了大型无脊椎动物的delta13和delta 15N特征，并增加了物种的丰富度适用于更宽松的环境。碳和氮稳定同位素分析（SIA）用于证明和解释安大略省西南部冷水上游水流中海狸蓄水区上下物种之间的差异。 δ13​​C和δ15N信号在每个范围内均不随季节或年份变化，但食物网多边形表明碳特征已耗尽，氮素特征相对于蓄水区上方的河段富集了下游。在海狸蓄水的河床上没有树冠覆盖物，促进了当地动物的生长，这反过来又导致了无脊椎动物生物量的增加和食物网的复杂性。水生植物增加的沉降和吸收以及高强度的阳光照射促进了快速生长的环境，导致对δ15N的歧视程度降低，从而导致在河狸蓄水区整体吸收了delta15N。

著录项

  • 作者

    Robinson, Laura.;

  • 作者单位

    University of Waterloo (Canada).;

  • 授予单位 University of Waterloo (Canada).;
  • 学科 Environmental Sciences.;Hydrology.;Biology Ecology.
  • 学位 M.Sc.
  • 年度 2006
  • 页码 92 p.
  • 总页数 92
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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