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首页> 外文期刊>Freshwater science >Influence of stream-floodplain biogeochemical linkages on aquatic food web structure along a gradient of stream size in a tropical catchment
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Influence of stream-floodplain biogeochemical linkages on aquatic food web structure along a gradient of stream size in a tropical catchment

机译：流域平原上河流-洪泛平原生物地球化学联系对水生食物网结构的影响

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We measured nutrients and dissolved organic matter (DOM) in surface water and floodplain sediments to evaluate biogeochemical linkages between streams and floodplains in 3 streams of increasing size in a tropical catchment in northwestern Australia. We hypothesized that stream-floodplain biogeochemical connectivity, measured as similar DOM concentrations and spectroscopic properties of streamwater and floodplain sediment leachate, would decrease with increasing stream size. We expected decreasing connectivity to shift support of aquatic foodweb structure from mainly allochthonous C in small streams to algal C in larger streams. Streamwater and sediment leachate concentrations of NH4-N, NO3-N, soluble reactive P, and DOM varied several-fold across the 3 sites but showed no strong pattern in stream-floodplain connectivity with increasing stream size. Fluorescence index, specific ultraviolet absorbance, and 813C-dissolved organic C (DOC) for stream water and sediment leachate were most similar to each other at the mid-size Adcock River, indicating tight river-floodplain biogeochemical connectivity via input of allochthonous DOM and NH4-N to stream water. 613C and δ15N signatures for key producers and consumers for all 3 streams showed that invertebrate consumers probably were supported by a range of in-stream (e.g., benthi? and filamentous algae) and floodplain (allochthonous leaf litter) sources, whereas fish strongly reflected δ13C-enriched sources (e.g., benthic algae). Allochthonous C was probably only a minor energy source for metazoa, but we propose that river-floodplain biogeochemical linkages may-be important for other aspects of ecosystem productivity, such as input of inorganic nutrients to support in-stream primary production. Terrestrial-aquatic biogeochemical linkages may be critical but poorly quantified components of river-floodplain ecosystems.
机译：我们测量了地表水和洪泛区沉积物中的养分和溶解性有机质（DOM），以评估澳大利亚西北部热带集水区中3条大小不断增加的河流中河流与洪泛区之间的生物地球化学联系。我们假设河流-洪泛区生物地球化学连通性（以相似的DOM浓度和河流水与洪泛区沉积物渗滤液的光谱性质来衡量）将随着河流规模的增加而减少。我们预计连通性的下降将使水生食物网结构的支持从小溪流中的主要异源碳转移到大溪流中的藻类碳。 NH4-N，NO3-N，可溶性反应性P和DOM的河水和沉积物浸出液浓度在3个位置上变化了几倍，但随着河道尺寸的增加，河道-洪泛区连通性没有显示出很强的模式。中型阿多克河的溪流水和沉积物渗出液的荧光指数，比紫外线吸收率和813C溶解的有机碳（DOC）彼此最相似，表明通过异源DOM和NH4的输入，河水泛滥的生物地球化学联系紧密-N放水。所有3种溪流的主要生产者和消费者的613C和δ15N签名显示，无脊椎动物的消费者可能受到一系列溪流资源（例如，本底和丝状藻类）和洪泛区（散落性叶子凋落物）的支持，而鱼类强烈反映了δ13C -丰富的来源（例如底栖藻类）。异源碳可能只是后生动物的一种次要能源，但是我们认为，河漫滩生物地球化学联系对于生态系统生产力的其他方面可能是重要的，例如输入无机养分以支持河流初级生产。陆地-水生生物地球化学联系可能是至关重要的，但是河洪平原生态系统的组成部分定量化程度很低。

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