Carbon cycle in Lake Suwa (maximum depth : 6.7 m;area : 14.5 km²) which is a highly polluted and eutrophic lake in Nagano Prefecture, Japan, was studied by determining pH and total carbon dioxide as follows :
(1) Total carbon dioxide (Total CO₂) of the lake water was determined by KOYAMA's method. The same water sample was aerated in order to be equilibrated with air. Total CO₂ of the aerated water sample was determined as an original total carbon dioxide (Orig. CO₂).
In the stably stratified lake waters, the difference (ΔCO₂) between Orig. CO₂ and Total CO₂ corresponds to the net fixation of CO₂ (N. Fix. CO₂) in a case of positive value and the net formation of CO₂ (N. Form. CO₂) in a case of negative value.
In the case of Lake Suwa, however, it should be suitable to call the former as the preserved amount of net fixation of CO₂ (P. A. N. Fix. CO₂) and the latter as the preserved amount of net formation of CO₂ (P. A. N. Form. CO₂), because the lake water layers are easily mixed and some of the dissolved CO₂ may be exchanged for the atmospheric CO₂ through all seasons.
From a vertical distribution of ΔCO₂, P. A. N. Fix. CO₂ or P. A. N. Form. CO₂ in a water column was calculated on the basis of (g C/m²).
(2) Relation curves between pH and Total CO₂ of the lake water were constructed from pH and Total CO₂ values obtained from the water samples collected in different months.
(3) Greater part of the numerous data of Total CO₂ values used in this study were estimated from a large number of vertical distributions of pH values obtained at different times in different days while comparing with the relation curves between pH and Total CO₂.
(4) Average P. A. N. Fix. CO₂ (A. P. A. N. Fix. CO₂) and average P. A. N. Form. CO₂ (A. P. A. N. Form. CO₂) in a whole day were estimated from the values of P. A. N. Fix. CO₂ and P. A. N. Form. CO₂ in a water column, which were estimated at different times in the day.
(5) Numerous data of these A. P. A. N. Fix. CO₂ or A. P. A. N. Form. CO₂ in the water column were estimated on different days in different months.
(6) A histogram of A. P. A. N. Fix. CO₂ and A. P. A. N. Form. CO₂ was then constructed against months.
(7) This histogram shows the following facts : (a) A. P. A. N. Fix. CO₂ ranged between 3.8 and 6.6 g C/m² from April through August. (b) A. P. A. N. Form. CO₂ ranged between -8.2 and -12.9 g C/m² from September through December. (c) On the assumption that the average exchangeability of CO₂ between air and lake water in a month is similar to those of the adjacent months, the difference between A. P. A. N. Fix. CO₂ or A. P. A. N. Form. CO₂ of a month and that of an adjacent month corresponds to the average net fixation rate of CO₂ during the two months in a case of positive value and to the average net formation rate of CO₂ in a case of negative value. (d) The average net fixation rate of CO₂ and the average net formation rate of CO₂ correspond to the average net production rate and the average net decomposition rate of organic matter respectively.
(8) The maximum net production rate which was found between March and April amounted up to 4.5 g C/m². day and the maximum net decomposition rate which was found between August and September amounted up to-13.5 g C/m². day.

抄録全体を表示

The Urabandai Lake Group consisting of about 80 lakes and ponds was formed by the eruption of the Volcano Bandai in 1888. The waters of these lakes are similar in nature in having sulphuric or hydrochloric acid in high concentrations. Lake Tatsu-numa is one of such lakes. Lake Tatsu-numa was selected as the IBP water area for two reasons : (1) all trophic levels from primary producers to higher consumers are present, and (2) the lake is comparatively small and is convenient for censuring by a few researchers.
As a part of the studies on the biological productivity in the disharmonic waters in the JIBP-PF The Urabandai Lake Group consisting of about 80 lakes and ponds was formed by the eruption of the Volcano Bandai in 1888. The waters of these lakes are similar in nature in having sulphuric or hydrochloric acid in high concentrations. Lake Tatsu-numa is one of such lakes. Lake Tatsu-numa was selected as the IBP water area for two reasons : (1) all trophic levels from primary producers to higher consumers are present, and (2) the lake is comparatively small and is convenient for censuring by a few researchers.
As a part of the studies on the biological productivity in the disharmonic waters in the JIBP-PF section, the author has engaged in research on the primary production since 1967, especially the plankton production in Lake Tatsu-numa.
(1) Lake Tatsu-numa is situated at the central portion of the Goshiki-numa Lake Group (Fig. 1). Its water contains such ions in high concentrations as SO₄^-- (237mg/l), Ca⁺⁺ (61.6mg/l), and Na⁺ (67.5mg/l), and has a pH of 6.4 (5.9-6.9) (KATO & AITA, 1970) (Fig. 2). Under such environmental conditions, there were found in this lake about 43 species of phytoplankton, among which, the following 9 species were selected by ADACHI (1970) as the important phytoplanktonic species in Lake Tatsu-numa. They are : Oscillatoria pseudogeminata, Melosira granulata, M. italica, Nitzschia obtusa var. scalpeiiiformis, Surireiia sp., Gymnodinium ordinatum, Peridinium inconspicuum, Scourfieldia cordiformis, and Tracheiomonas volvocina.
(2) The standing crop of the phytoplankton in Lake Tatsu-numa varied from 40.5 to 557.4 in the number of cells per 1 millilitre during these five years. The chlorophyll-a content showed the value from 0.136 to 2.5mg/m³ and from 0.5 to 9.1 mg/m², and the energy efficiency in the gross production ranged from 0.0042 to 0.036% throughout the year. The carbon uptake obtained by ¹⁴C-experiments was 19.97 mg/m²/day in November, 1971. On the basis of these results, Lake Tatsu-numa is classified into an oligotrophic type (Figs. 4-6, Table 1).
(3) In the marginal shrub zone of Lake Tatsu-numa, there were found abundantly Oedogonium sp. and diatoms (Fig.8), which grew to a large biomass by autumn. The standing crop of these littoral sessile algae was estimated to be 10.77 kg in dry weight in November, 1971 for the lake as a whole. Moreover, the algal mat consisting of Vaucheria hamata, Niteiia sp., and diatoms developed over the bottom surface of the lake (Fig. 9). The standing crop of such benthic algae was estimated by SHOJI and SHISHIDO (1972) to be 65 kg in dry weight and about 500 kg in fresh weight in November, 1971.
The standing crops of phytoplankton, sessile algae in the marginal shrub zone, and of benthic algae on the lake bottom were estimated to be 4.2kg, 10.77kg, and 65kg in dry weight, respectively in the late autumn. Their percentages to the whole were 5.25%, 13.5%, and 81.3%, respectively, their ratios to the phytoplankton being 1 : 2.6 : 15.5, respectively.

抄録全体を表示

1. Aquatic small animals collected in the littoral region of Lake Yuno-ko on November3, 1968 were investigated concerning the contents of their digestive tracts.
2. One individual of Ephemera sp. (Ephemeroptera) seems to take algae attached to the shore or deposited on the bottom.
3. A large quantity of algae was found in 11 individuals of Nemoura sp. (Plecoptera). It seems likely that they take attached or deposited algae.
4. As regards Trichoptera, only each one individual of Goera japonica and Polycentropus sp. and an undetermined species were examined concerning their foods. Goera japonica mainly takes attached or deposited algae, while Polycentropus sp. takes abundantly either floating Chlamydomonas sp. or that which may be a zoospore of any green alga. In the digestive tract of the species of undetermined genus contains abundant planktonic diatoms.
5. No alga was found in Platambus sp. (Coleoptera) Helichus sp. belonging also to the same order takes a large quantity of attached algae.
6. The main contents of the digestive tracts of 21 individuals of a crustacean, Asellus sp. are Chlamydomonas sp., Melosira italica f, curvata, Ulothrix sp. and Fragilaria sp., all of which are the species mostly attached to fallen leaves on the lake bottom.
7. For comparison of similarity in the composition of algal flora in the digestive tracts of the larval samples collected at the same place, it is attempted to analyse according to the c'_λ method.
8. The floral composition is similar among Nemoura sp. and among Asellus sp. It implies that the composition of the flora in the same species of aquatic small animals is similar, but that similarity is not found between the different species.
s. In regard to the construction of the flora in the digestive tracts of the same species collected at the different places, a great similarity is found in the individuals collected at the resembling environments, while there is less similarity between the individuals collected at the different environments.
Such a phenomenon will attribute to the construction of different algal communities at the different environments.

抄録全体を表示

This paper deals with the seasonal variation of body length of Sinodiaptomus volkanoni KIEFER, collected from small ponds near Miki City, Hyogo Prefecture, from August, 1967 to July, 1970. With regard to its body length, two different types could be found i. e., a small-sized group occurring in the warm season (autumn) and a large-sized group in the cold season.
The seasonal changes in length of the head, thorax and abdomen were also found. The maximum percentage of head length to body length was met with in the warm season and the minimum in the cold season. On the contrary, the maximum percentage of abdomen length to body length was found in the cold season and the minimum in the warm season.
However, the thorax length to body length, regarding its maximum percentage, was sporadic to some extent.
In the specimens collected in winter it was observed that reddish orange oil drops were deposited in the body, but, as the season progressed, they gradually decreased and entirely disappeared in summer.

抄録全体を表示