Analysis of nitrogen and phosphorus transfer through aquatic food webs.

为了研究水环境中碳(C)、氮(N)和磷(P)通过食物网的转移过程，对不同浮游生物中这些元素的含量进行了测定。以欧瓦湖为富营养化水体为例，以冈玉湖为贫营养水体为例，选取两个研究点采集浮游生物样品。在实验室研究中，评估了氮和磷对细菌、浮游植物和浮游动物的生长和生产的影响，并考虑了食物网的作用。以下信息来自对分级浮游生物样品的化学分析。1.通常情况下，柳杉样品的N/C和P/C比值高于大田柳杉样品。2.浮游动物的这两个比值高于浮游植物，N/C是N/C的2倍，P/C是P/C的4倍，说明在它们的放牧活动中元素的凝聚是必要的。3.计算细菌细胞中C、N含量，细胞体积为0.06~0.19pgC/um，平均N/C为0.203。一项利用H-胸腺嘧啶核苷摄取的实验表明，磷是一个贫营养化湖泊中细菌生产的限制营养物质。浮游动物的生长和元素组成受食用浮游植物中N、P含量的影响，特别是在低食物浓度下。这些结果表明，细菌和浮游动物并不一定像以前认为的那样，在水环境中发挥营养再生的作用。

In order to study the processes of carbon(C), nitrogen(N) and phosphorus(P) transfer through food webs in aquatic environments, contents of these elements in various plankton organisms were determined. Two study sites, Lake Ouwa as an example of eutrophic waters and lake okutama as oligotrophic ones, were selected to obtain planktonic samples. In laboratory studies the effects of nitrogen and phosphorus on the growth and production of bacteria, phytoplankton and zooplankton were assessed and the role of food webs was considered. The following information was obtained from the chemical analysis of size fractionated plankton samples. 1. Generally, higher N/C and P/C rations were recorded in L. Suwa samples than those from L. Okutama. 2. These two ratios were higher in zooplankton than phytoplankton; two times in N/C and four times in P/C, suggesting the necessity of condensation of the elements in their grazing activity. 3. C and N contents in bacterial cells were estimated; 0.06 to 0.19 pgC/um cell volume and 0.203 in mean N/C ratio. An experiment using H thymidine uptake revealed that phosphorus was a limiting nutrient for bacterial production in an oligotrophic lake. It was also shown phytoplankton production was controlled by P and N. The growth and element composition of zooplankton were affected by N and P-content of food phytoplankton especially under low food concentration. These results show that bacteria and zooplankton do not necessarily play the role of nutrient regeneration in aquatic environments as previously believed.