Lake Kizaki

Sampling. Water and sediments were sampled at the greatest depths of two mountain mesotrophic lakes in Nagano Prefecture, Lakes Kizaki-ko and Nakatsuna-ko. Sampling of the core sediments was made by using a core sampler devised by the author. 

Ratios of Organic Carbon and Nitrogen in Settling Detritus. The ratios of Org. C/Org. N of plankton, sediments collected at 25 meters in water, and surface bottom sediments in Lake Kizaki-ko are 5.7, 9.3, and 15.5, respectively (Table I). 

Table I. Average Ratio Organic C/Organic N of Plankton, Detritus Settled at the 25-Meter level and Surface Bottom Sediments in lake Kizaki-ko...

In order to clarify the mechanism of microbiological decomposition of organic carbon and nitrogen of detritus in the lake water, the gaseous and nitrogenous components as well as the other chemical characteristics were determined in Lake Kizaki-ko, September 7-8, 1963 and October 28-31, 1963 when stagnation had greatly advanced in the lake. 

Org. C was estimated on the assumption that the ratio C/Loss on ignition of these samples is equal to the average ratio (0.428) of sediments from Lakes Kizaki-ko and Nakatsuna-ko. 

Figure 3. Vertical distribution of various components in Lake Kizaki-ko...

Table IV. Gaseous Components in Core Sample of Sediments from lake Kizaki-koa...

TabU XI. Vertical Variation of Organic Carbon, Nitrogen, and Hydrogen in a Core Sample of Sediments from Lake Kizaki-ko, Which Was Previously Dried8... 

From the vertical distributions of various components, the mineralized carbon (Miner. C) and nitrogen (Miner. N) at various depths were calculated. On the basis of the calculated values, the ratio of Miner. C/Miner. N in a vertical water column of Lake Kizaki-ko was estimated to be 2.83, which is considerably smaller than that of plankton. 

The carbonaceous, nitrogenous, and hydrogenous components in a core sediment from Lake Kizaki-ko were determined. The ratios of Org. C/Org. H and of Org. N/Org. H in the core sample increase regularly with increasing depth. 

Subsequent nitrification ofthis ammonium, and denitrification of the resulting nitrate, both discriminate strongly against N (Table I). In the last case, selective loss of the resulting " N2 may leave an isotopically enriched residualDINpool, particularly when denitrification occurs within the water column. An example is provided by Lake Kizaki, Japan, where during the summer stratification period the of the residual deepwater N03 was found to be +15.1%c, whereas shallow-water NO3 had a of -2.2 (Yoshioka et al 1988). 

Yoshioka, T, H. Hayashi E. Wada, 1989. Seasonal variations of carbon and nitrogen isotope ratios of plankton and sinking particles in Lake Kizaki. Japan. J. Limnol. 50 313-320. 

Yoshioka, T, E. Wada Y. Saijo. 1988. Isotopic characterization of Lake Kizaki and Lake Suwa. Japan. J. Limnol. 49 119-128. 

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