A large number of studies across many different disciplines have been conducted on the Swartvlei estuarine system over the past five decades, thus providing an ideal opportunity to review spatial and temporal aspects of fish food webs in the lower estuary and upper lake. The aquatic and semi-aquatic macrophytes, together with the physico-chemical environment associated with these two parts of the system are very different, thus providing an immediate contrast in terms of habitat functioning for the associated fish assemblages. In addition, major macrophyte senescence is known to occur episodically in Swartvlei Lake, bringing with it major consequences for the trophic functioning of that part of the system. The scientific information on the Swartvlei estuarine lake system is reviewed and conceptual trophic diagrams created that encapsulate both the spatial and temporal aspects described above. The next step in our understanding of the trophic functioning of the Swartvlei system is to undertake stable isotope analyses in both the lake and estuary. To prepare for such a step, the global literature on the use of stable isotopes in estuaries is reviewed and some of the findings, particularly in relation to fishes and food webs in different habitats, are highlighted. One of the conclusions reached by this review is that microalgae, whether epipsammic, epiphytic and/or planktonic, have been under-estimated relative to estuarine macrophytes in terms of their importance to the nutrition and productivity of fishes in estuaries. The central role of detritus and associated microorganisms in providing trophic stability for invertebrates and fishes in estuaries is also highlighted. Finally, it is apparent that fishes do not rely on a single source of organic matter for growth and development, e.g. most carnivorous fish species rely on mixes of prey that use different organic sources for production, and that benthic/demersal fishes in particular seem to access food chains from different parts of the water column.

中文翻译：

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南非河口的鱼类食物网：空间和时间评估

在过去的五年中，对 Swartvlei 河口系统进行了许多不同学科的大量研究，从而提供了一个理想的机会来审查下河口和上湖鱼类食物网的空间和时间方面。水生和半水生大型植物以及与系统这两个部分相关的物理化学环境非常不同，因此在相关鱼类组合的栖息地功能方面提供了直接的对比。此外，已知主要大型植物衰老会在 Swartvlei 湖中偶发性发生，从而对系统该部分的营养功能产生重大影响。审查了有关 Swartvlei 河口湖系统的科学信息，并创建了包含上述空间和时间方面的概念营养图。我们理解 Swartvlei 系统营养功能的下一步是在湖泊和河口进行稳定同位素分析。为准备这一步骤，审查了关于在河口使用稳定同位素的全球文献，并重点介绍了一些发现，特别是与不同栖息地的鱼类和食物网有关的发现。本综述得出的结论之一是，微藻，无论是附生的、附生的和/或浮游的，相对于河口大型植物，就其对河口鱼类的营养和生产力的重要性而言，都被低估了。还强调了碎屑和相关微生物在为河口无脊椎动物和鱼类提供营养稳定性方面的核心作用。最后，很明显，鱼类的生长和发育并不依赖单一的有机物质来源，例如，大多数肉食性鱼类依赖于使用不同有机来源进行生产的混合猎物，尤其是底栖/底栖鱼类似乎从水体的不同部分访问食物链。