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首页> 外文期刊>Marine ecology progress series >Carbon and nitrogen system dynamics in three small South African estuaries, with particular emphasis on the influence of seasons, river flow and mouth state
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Carbon and nitrogen system dynamics in three small South African estuaries, with particular emphasis on the influence of seasons, river flow and mouth state

机译：南非三个小河口的碳和氮系统动力学，特别强调季节，河流流量和河口状态的影响

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摘要

The importance of fluctuations in rainfall and riverine flow on ecosystem functioning in a permanently open estuary (POE), the Mlalazi, and 2 temporarily open/closed estuaries (TOCEs), the East Kleinemonde and Mpenjati, were investigated. These systems, located on the east coast of South Africa, are strongly influenced by seasonal changes in rainfall and river flow. Most TOCEs are open to the sea during the wet season and closed during the dry season. Ecosystem models based on ecological network analysis were applied to the data, using both carbon (C) and nitrogen (N) as model currencies. The analyses indicated that the dependency of consumers on primary producers was higher during the closed phase than the open phase in TOCEs, which was attributed to the higher phytoplankton and microphytobenthos standing stocks during the former phase. Higher trophic efficiencies at trophic level (TL) 1 (primary producers) were recorded for C and N networks in the TOCEs during the open phase, while in the Mlalazi Estuary the trophic efficiency at TL 1 was highest during the dry season. The detritivory: herbivory ratio and total system throughput (TST) reflected the seasonal variations in the phytoplankton and microphytobenthos standing stocks within the estuaries. Cycling indices suggested that more N was recycled during TOCE closed phases and during the POE dry season. The contrasting results between the dry and wet seasons in the 3 estuaries, as well as the opposite system-level responses within TOCEs and POE, clearly emphasised the importance of seasonal variations in river flow and mouth state to ecosystem level functioning.
机译：研究了降雨和河流流量波动对永久性开放河口（POE），Malalazi和2个临时开放/封闭河口（TOCE），东克莱因蒙德和姆彭贾蒂的生态系统功能的重要性。这些系统位于南非的东海岸，受到降雨和河流流量的季节性变化的强烈影响。大多数TOCE在雨季向海开放，在旱季不开放。将基于生态网络分析的生态系统模型应用于数据，同时使用碳（C）和氮（N）作为模型货币。分析表明，在封闭阶段，消费者对初级生产者的依赖程度高于开放阶段，这归因于前一阶段浮游植物和微型底栖鱼类的较高存量。在开放阶段，TOCE中的C和N网络在营养水平（TL）1（主要生产者）处记录到较高的营养效率，而在Malalazi河口，干燥季节中TL 1的营养效率最高。有害物质：草食动物的比例和总系统吞吐率（TST）反映了河口浮游植物和微型底栖鱼类的种群季节性变化。循环指数表明，在TOCE封闭阶段和POE干旱季节，有更多的N被循环利用。 3个河口的干湿季之间的对比结果，以及TOCEs和POE中相反的系统级响应，清楚地强调了河流流量和河口状态的季节性变化对生态系统功能的重要性。

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