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Assessing the extent and relative risk of aquatic stressors on stream macroinvertebrate assemblages in the neotropical savanna
Science of the Total Environment ( IF 9.8 ) Pub Date : 2018-03-21 , DOI: 10.1016/j.scitotenv.2018.03.127
Déborah R.O. Silva , Alan T. Herlihy , Robert M. Hughes , Diego R. Macedo , Marcos Callisto

Freshwater ecosystems are among the most threatened by human activities, influencing losses of biodiversity. To efficiently address management practices to conserve and restore those ecosystems it is important to correctly identify and quantify the severity and magnitude of anthropogenic stressors degrading freshwater biota. In this study we assessed seven stressors describing poor water quality, physical habitat alteration, and land use by means of the relative risk (RR) and relative extent (RE) approach. The RR measures the co-occurrence probability of high stressor condition and poor biological condition. The RE measures the proportion of stream length in the region in high stressor condition. To obtain accurate estimations of RR and RE we used a probabilistic survey design to select a representative sample of perennial, wadeable and accessible streams within four hydrologic units in the neotropical savanna. Results were evaluated at two spatial scales: local – within each of the four hydrologic units, and regional – all four units combined. From 143 randomly selected sites we inferred our results to a target population of 9466 km of streams. Regionally, we found turbidity, % fine sediments and % agriculture as key stressors associated with poor biological condition. At the local scale, we also found that % pasture and total nitrogen were key stressors of biological condition, but their extent was relatively small. By evaluating both RR and RE we conclude that reducing excess sedimentation on streambeds should be the most effective means of improving biological condition over the region. That finding should guide decision makers and land managers to better focus their efforts and resources on improving biological condition of savanna streams.



中文翻译:

评估新热带稀树草原中水生应激源对大型无脊椎动物组合的程度和相对风险

淡水生态系统是人类活动最严重的威胁之一,影响着生物多样性的丧失。为了有效应对保护和恢复这些生态系统的管理实践,正确识别和量化破坏淡水生物群的人为压力源的严重性和严重性很重要。在这项研究中,我们通过相对风险(RR)和相对程度(RE)方法评估了七个压力因子,描述了不良的水质,自然的栖息地变化和土地利用。RR衡量高压力条件和不良生物条件的同时发生概率。RE测量高应力条件下该区域中水流长度的比例。为了获得对RR和RE的准确估算,我们使用了概率调查设计来选择代表性的多年生植物样本,在新热带稀树草原的四个水文单元中,存在可通行的水流。在两个空间尺度上对结果进行了评估:局部-在四个水文单元中的每个区域,以及区域-所有四个单元的组合。从143个随机选择的站点中,我们将结果推断为9466 km的目标流。在区域上,我们发现浊度,细小沉积物百分比和农业百分比是与不良生物状况相关的主要压力源。在地方尺度上,我们还发现%的草场和总氮是生物条件的关键压力源,但它们的范围相对较小。通过评估RR和RE,我们得出结论,减少河床过多的沉积物应该是改善该地区生物状况的最有效手段。

更新日期:2018-03-22
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