Abstract The nature and quality of basal resources within aquatic food webs are complex and have the potential to shift over space and time. We used fatty acid analysis to assess variations in the nutritional structure of the suspended and basal pools along an entire river system, and to assess the contributions of vascular plant (i.e., mainly of terrestrial origin, but could include aquatic macrophytes) vs algal (i.e., aquatic origin) sources to the suspended particulate matter (SPM) pools. Samples were collected in a temperate South African river on four occasions between September 2012 and June 2013. We found orderly patterns in the fatty acid composition of the basal resources at the sites during most seasons. Regardless of site or season, the benthic algal pools (epiphyton, epipelon and epilithon) were the most nutritionally rich resources based on essential fatty acid contents and diatom indices. During early and late spring, proportions of essential fatty acids in the epiphyton decreased downstream where increased light was available, consistent with predictions from the light:nutrient hypothesis (but inconsistent with epilithon and epipelon results). There were substantial changes in vascular plant contributions to the SPM pools along the river, but the same patterns were not produced in all seasons. Of all the river models considered, the data were more consistent with the riverine productivity model, which particularly emphasises the importance of autotrophic production in rivers. Our study provides new detail on the complexity of basal resource nutritional quality and how it can shift along a lotic system over time.

中文翻译：

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温带河流/河口连续体沿线基础资源营养质量的时空变异性

摘要 水生食物网中基础资源的性质和质量是复杂的，具有随空间和时间变化的潜力。我们使用脂肪酸分析来评估整个河流系统中悬浮池和基底池营养结构的变化，并评估维管植物（即主要来自陆生，但可能包括水生大型植物）与藻类（即, 水生来源) 源到悬浮颗粒物 (SPM) 池。2012 年 9 月至 2013 年 6 月期间，我们在南非温带河流中四次采集样品。我们发现在大多数季节，这些地点的基础资源的脂肪酸组成具有有序的模式。无论地点或季节如何，底栖藻类池（附生藻、Epipelon 和 epilithon) 是基于必需脂肪酸含量和硅藻指数的营养最丰富的资源。在早春和晚春，附生植物中必需脂肪酸的比例在下游可用光增加的地方减少，这与光：营养假说的预测一致（但与附生和附生结果不一致）。维管植物对沿河 SPM 池的贡献发生了重大变化，但并非所有季节都产生相同的模式。在考虑的所有河流模型中，数据与河流生产力模型更加一致，特别强调了河流自养生产的重要性。