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首页> 外文期刊>Aquatic Sciences >Seasonal isotopic shifts in fish of the Pantanal wetland, Brazil
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Seasonal isotopic shifts in fish of the Pantanal wetland, Brazil

机译：巴西潘塔纳尔湿地鱼类的季节性同位素变化

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摘要

Seasonal inundations shape the floodplain characteristics of the Pantanal, a large wetland in Central South America. In the first study combining stable carbon and nitrogen isotope analysis with classical stomach content analysis in this region, we investigated the influence of the annual inundation on diet and isotopic composition of floodplain fish. Apart from potential food items, 33 fish species from the Coqueiro Lake were analyzed, 10 of which were present during both the wet and dry season 1999. A δ~(13)C and δ~(15)N plot of the floodplain ecosystem allowed us to assess a foodchain of 3-4 trophic levels. However, the wide overlap of nitrogen values suggested that the organisms act on trophic continua rather than on distinct levels. The foodweb was based mainly on C_3-plant carbon. However, fish species capable of feeding on terrestrial invertebrates (e.g., Brycon microlepis) had δ~(13)C values above -25 per thousand, indicating 13-30% intake of C_4-plant based carbon during the flooding period. The novel use of vector coordinates and 2-dimensional ANOVA showed that the seasonal isotopic shifts of δ~(13)C and δ~(15)N were highly significant for some feeding guilds. δ~(15)N values increased from the wet to dry season in most fish species, and these shifts were highly significant for omnivores (Astyanax bimaculatus, Triportheus nematurus, Tetragonopterus argenteus and Moenkhausia dichroura), and significant for invertivores (Gymnogeophagus bal-zanii and Poptella paraguayensis) and carnivores (Ser-rasalmus spilopleura). Average carbon isotope ratios decreased at the same time in the herbivores (Methynnis mola: 3.4 per thousand) and detritivores (Psectrogaster curviven-tris: 5.3 per thousand), but they did not change in the hypostomatic herbivore Sturisoma robustum. We explain these shifts by abundant and variable food sources during the inundation period and increasing carnivory and starvation during the dry season when the lake is confined to its central basin. Isotopic shifts between seasons were more prominent in less specialized species of omnivores, invertivores and some carnivores, whereas more specialized herbivores and detritivores appeared to be more influenced by changes in the carbon isotope ratio of the diet affected by biogeochemical processes such as respiration and methanogenesis. A general model for the interpretation of isotope data of floodplain fish considering different time-scales is given.
机译：季节性淹没影响了南美中部大湿地潘塔纳尔湿地的洪泛区特征。在该地区将稳定的碳和氮同位素分析与经典胃含量分析相结合的第一项研究中，我们调查了年度淹水对洪泛鱼的饮食和同位素组成的影响。除了潜在的食物外，还分析了来自科奎罗湖的33种鱼类，其中10种在1999年的湿季和旱季都存在。洪泛区生态系统的δ〜（13）C和δ〜（15）N图我们评估了3-4个营养级别的食物链。然而，氮值的广泛重叠表明生物体在营养连续体而不是在不同水平上起作用。食物网主要基于C_3植物碳。然而，能够以陆生无脊椎动物为食的鱼类（例如Brycon microlepis）的δ〜（13）C值高于每千分之-25，这表明在洪水期间C_4植物基碳的摄入量为13-30％。向量坐标和二维方差分析的新颖用法表明，对于某些饲养行会来说，δ〜（13）C和δ〜（15）N的季节性同位素变化非常显着。在大多数鱼类中，δ〜（15）N值从干季到干季均增加，这些变化对于杂食动物（Astyanax bimaculatus，Triportheus nematurus，Tetragonopterus argenteus和Moenkhausia dichroura）非常重要，而对无食食动物（Gynnogeophagus bal-zanii）则非常重要。和Paraguayensis Poptella）和食肉动物（Ser-rasalmus spilopleura）。食草动物（Methynnis mola：千分之3.4）和碎屑动物（Psectrogaster curviven-tris：千分之5.3）的平均碳同位素比在同一时间下降，但在具假说性的草食性鲁棒肉中，平均碳同位素比没有变化。我们解释了这些变化的原因：在淹没期，食物来源丰富且变化多端；在干旱季节，当湖泊局限于其中心盆地时，食肉和饥饿增加了。在杂食性，无食食性和某些食肉动物等较不特殊的物种中，季节之间的同位素变化更为明显，而受生物地球化学过程（如呼吸作用和产甲烷作用）影响的饮食中碳同位素比的变化，则更特殊的食草动物和碎屑动物似乎受到更大的影响。给出了考虑不同时间尺度的洪泛区鱼类同位素数据解释的通用模型。

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