Lake Suwa Research Articles

複合的な対策による諏訪湖水環境改善および副次的CO<sub>2</sub>排出による地球温暖化への影響の統合的評価

複合的な対策による諏訪湖水環境改善および副次的CO<sub>2</sub>排出による地球温暖化への影響の統合的評価

1. 諏訪湖におけるユスリカ類幼虫の水平分布について(第53回日本衛生動物学会東日本支部大会講演要旨)

1. 諏訪湖におけるユスリカ類幼虫の水平分布について(第53回日本衛生動物学会東日本支部大会講演要旨)

Mechanism and prediction for contamination of freshwater bivalves (Unionidae) with the cyanobacterial toxin microcystin in hypereutrophic Lake Suwa, Japan.

Seasonal changes of microcystin (MC) bioaccumulation in three freshwater Unionid bivalves, Anodonta woodiana, Cristaria plicata, and Unio douglasiae, were investigated in the hypereutrophic Lake Suwa. Total MC concentrations (MC-RR and -LR) as determined by reverse-phase high-performance liquid chromatography were at high levels in the hepatopancreas of C. plicata and U. douglasiae, with maxima at 297 and 420 microg/g dry weight, respectively. The amounts and seasonal changes in the accumulated MC concentration differed in all species. The total MC concentration of A. woodiana was always less than that of other species (maximum concentration of 12.6 microg/g dry weight). The toxin concentration of C. plicata remained very low in summer, when the Microcystis bloom occurred, but increased rapidly in autumn, when the toxic bloom disappeared. For U. douglasiae, simple regression analyses were performed to clarify the relationship between MC bioaccumulation and environmental parameters such as water temperature, chlorophyll a, suspended solids (SS), intracellular MC per unit volume of lake water and per-unit weight of SS and extracellular MC. The toxin concentration of U. douglasiae correlated more closely with qualitative factors, with intracellular toxin per SS (p < 0.001, R(2) = 0.72) than with quantitative factors such as chlorophyll a and intracellular toxin per unit volume of lake water. No correlation could be found between MC in the tissues and extracellular MC. These results indicate that a long-term survey is needed to assess the safety of bivalves. The study should take into consideration both interspecific differences in toxin content and what is the optimal monitoring parameter.

EVALUATION OF TRADE-OFF RELATION BETWEEN THE IMPROVEMENT OF REGIONAL ENVIRONMENT WITH AN INTRODUCTION OF ENVIRONMENTAL TECHNOLOGIES AND THE IMPACT OF IT ON GLOBAL WARMING BY CO2 EMISSION

Objectives of this study are building and applying methodologies to evaluate trade-off relation between the improvement of regional environment with an introduction of environmental technologies and the impact of it on global warming by CO2 emission.In this study, reduction of target load and emission of additional CO2 are calculated and converted to an economic value to evaluate trade-off relation. And some methodologies, which enable to consider regional characteristics, are applied to estimate an economic value of the improvement of regional environment. In addition, marginal social cost of CO2 emission is applied to estimate an economic value of the impact of global warming. Along with methodologies shown above, improvement technologies for water environment of Lake Suwa in Nagano prefecture were evaluated as a case.As results of this study, the improvement of water environment was simulated by ecosystem model, and using Contingent Valuation Method, the economic value of it was estimated as 728 million/ year. On the other hand, CO2 emission was calculated by applying inventory analysis of LCA, and the maximum value of global warming was estimated as 30million/ year by using marginal social costs. It can be inferred that both technologies are effective within environmental aspects of eutrophication and global warming.

Determination of microcystins in lake water using reusable immunoaffinity column

A reusable immunoaffinity column for purification of microcystins in lake water was prepared by coupling anti-microcystin-LR monoclonal antibodies to immunoaffinity support. Thanks to spherical shape of the immunoaffinity support Formyl-Cellulofine® used in this study, applied solutions passed the column smoothly even when used repeatedly. Reusability of the column was examined by determining the recoveries of spiked microcystins-RR, -YR and -LR (100ng each) from lake water. After extraction with a Sep-Pak PS2® cartridge containing styrene–divinylbenzene copolymer, the extract was purified with the immunoaffinity column. The immunoaffinity column was regenerated by washing with Tris–HCl buffer containing bovine serum albumin for repeated uses. Recoveries of spiked microcystins from the first use of the column were 87–88%, and 83–88% from the second and third uses, and the recoveries gradually dropped to 63–77% from the 4–5th uses, the results of which indicated that the column could be used repeatedly for three times. The present method was applied to determine microcystins in water collected from three different lakes in Japan in 1999. In a sample from Lake Suwa, microcystins-RR and -LR were determined by high performance liquid chromatography with photodiode array detection and electrospray ionization-liquid chromatography/mass spectrometry.

Application of an ecosystem model for aquatic ecological risk assessment of chemicals for a Japanese lake

The Lake Suwa version of the comprehensive aquatic systems model (CASM_SUWA) was developed using field data from Lake Suwa and evaluated to examine the utility of CASM_SUWA for assessing the ecological risk of chemicals for aquatic ecosystems. The calibration of the parameters for the model provided that the established reference model simulation could reproduce complex seasonal biomass behavior of populations that were not significantly different from the general seasonal pattern for the Lake Suwa ecosystem. The sensitivity analyses revealed the potential importance of indirect effects and demonstrated that the parameter values of all the trophic levels were important in determining the biomass of each trophic level in the model. The risk estimation of linear alkylbenzene sulfonates (LAS) demonstrated that the model estimated the risks of direct toxic effects on each population and the indirect ecological effects that propagate through the food-web in the model ecosystem. The CASM_SUWA-derived benchmark levels were approximately one order of magnitude less than the field-derived NOECs in literature. The analyses of the comparison implied that the model could provide a good basis in determining an ecological protective level of a chemical of concern in aquatic ecosystem. This modeling study demonstrated that the model can be used to provide additional information for the decision-making process in the management of the aquatic ecological risk of chemicals.

Female‐biased operational sex ratio of sexual host fish in a gynogenetic complex of Carassius auratus

To study the coexistence of sexual and gynogenetic forms, we examined the population structure of a gynogenetic complex of the Japanese crucian carp, Carassius auratus Temminck et Schlegel, during the April–June reproductive season by collecting 1225 mature fish that migrated from Lake Suwa to a tributary river for spawning. There were more sexual fish (about 80%) than gynogenetic fish in this complex, and the operational sex ratio in the sexual form was female biased (males were about 20%). Mean standard length and body weight of sexual females were larger than those of sexual males. Sex ratio was male biased in smaller fish (standard length, <8.5 cm) but female biased in larger fish (standard length, ≥8.5 cm). We determined age by scale ring marks; the average age of sexual females was higher than that of males, but there was no significant difference in the average age between sexual and gynogenetic females. Sex ratio in the sexual form was more female biased for old than for young fish, and the mean size of sexual females was larger than that of males of the same age. The clear female-biased sex ratio and age difference between sexual females and males can be explained either by (1) higher mortality of males or by (2) female-biased sex allocation. The latter process reduces the disadvantage of sex and contributes to the coexistence of sexual and gynogenetic forms.

Difference in parasite load and nonspecific immune reaction between sexual and gynogenetic forms of Carassius auratus

For coexistence, the sexual form in sexual/asexual complexes needs short-term advantages that can compensate for the two-fold disadvantage of sex. Higher mortality in the asexual form due to a higher parasite load will provide an advantage to the sexual form. In Lake Suwa, Japan, the parasite load (Metagonnimus sp.; Trematoda) of triploid gynogenetic females of Carassius auratus was significantly higher than that of diploid sexual females. In an immunoassay using healthy wild fish that were conditioned for 1 month in laboratory tanks, the nitroblue tetrazolium (NBT) immune reaction of sexual females was significantly higher than that of gynogenetic females. The NBT activity indicates the abundance of oxygen radicals from phagocytes, and hence the level of immune activity of the phagocytes. We suggest that the higher parasite load of the gynogenetic form is in part due to the lower immune activity of the phagocytes (nonspecific immune reaction) in the gynogenetic form compared to the sexual form.

Difference in parasite load and nonspecific immune reaction between sexual and gynogenetic forms of Carassius auratus

For coexistence, the sexual form in sexual/asexual complexes needs short-term advantages that can compensate for the two-fold disadvantage of sex. Higher mortality in the asexual form due to a higher parasite load will provide an advantage to the sexual form. In Lake Suwa, Japan, the parasite load (Metagonnimus sp.; Trematoda) of triploid gynogenetic females of Carassius auratus was significantly higher than that of diploid sexual females. In an immunoassay using healthy wild fish that were conditioned for 1 month in laboratory tanks, the nitroblue tetrazolium (NBT) immune reaction of sexual females was significantly higher than that of gynogenetic females. The NBT activity indicates the abundance of oxygen radicals from phagocytes, and hence the level of immune activity of the phagocytes. We suggest that the higher parasite load of the gynogenetic form is in part due to the lower immune activity of the phagocytes (nonspecific immune reaction) in the gynogenetic form compared to the sexual form.

近年の諏訪湖における生物群集の動態研究の意義

Studies of the organic community in Lake Suwa have been performed since 1907. During the long history of such studies, lake eutrophication reached serious levels in 1960s and 1970s, and eutrophication problems occurred. These studies have, therefore, reflected the changes in the community associated with lake eutrophication. In order to solve the resultant problems, a sewerage system was built in the lake catchment area in 1979, and the residential area covered by the system has increased since that time. Nevertheless, the lake water quality had not been markedly restored for about the last 20 years. Around 1997, however, the seasonal patterns in various parameters of the organic community started to change. This may indicate that ecosystem of Lake Suwa is changing associated with changes in lake water quality, which is being markedly restored. Therefore, since current studies are starting to show how the ecosystem responds to the water quality improvement, such studies should be intensified. To effectively conduct such studies in future, it is very important to review the results of recent studies on the organic community of the lake. For this purpose, five review papers were produced and are presented in this special issue. They concern chironomid populations, zooplankton, bloom-forming cyanobacteria and its toxins, and the fish community; all of which are characteristic of the Lake Suwa ecosystem. Three of them (papers on chironomids and zooplankton) are published in the present issue, while the remaining two will appear in the next issue.

諏訪湖水環境改善効果と対策に伴う地球環境への影響の費用便益換算による統合的評価

水環境改善対策の実施に際してはCO2などの環境負荷が増加する可能性がある. 本論文では, CVMやLCAなどの手法を組み合わせ環境改善対策にともなう地域環境および地球環境への影響の費用・便益換算による統合的評価を目的とし, ケーススタディとして長野県・諏訪湖における下水道整備および底泥浚渫について評価を試みた.まず, 諏訪湖集水域においてCVMを適用したアンケート調査を行い対策による諏訪湖の水環境改善便益を解析した結果, 年間7.3億円となった. 一方, 対策についてLCインベントリー分析を行い追加的CO2排出による地球温暖化の損害費用を算出した結果, 年間100万～2, 300万円となった. これらの結果から, 評価対象の対策は統合的にみて環境改善効果が大きいことが示された.

Co-production of microcystins and aeruginopeptins by natural cyanobacterial bloom.

The relationship between Microcystis composition and the production of microcystins and nontoxic peptides in bloom cells, which was regularly collected in Lake Suwa, Japan, in the summer season from 1991 to 1994, was investigated. In order to determine the structures of the nontoxic peptides, we collected large amounts of bloom materials from the same lake on July 23, 1991, and isolated three nontoxic peptides. They were named as aeruginopeptins 917S-A, -B, and -C, and their structures were mainly determined by a mass spectrometry/mass spectrometry (MS/MS) technique as 19-membered cyclic depsipeptides possessing the Ahp (3-amino-6-hydroxy-2-piperidone) moiety. An analysis of the microcystins and aeruginopeptins in the collected blood cells and their Microcystis composition suggested that the M. aeruginosa large cell size produces both microcystins and aeruginopeptins, and the production of both compounds is genetically closely related.

諏訪湖の生物群集の研究 諏訪湖におけるアオコ毒素ｍｉｃｒｏｃｙｓｔｉｎの動態

湖沼生態系におけるアオコ毒素ミクロキスチン(microcystin)の動態に関する研究が世界各国の研究者によって遂行されてきた。諏訪湖においてもいち早くmicrocystinの生産,吸着,物理化学的分解,生物蓄積そして生物分解に関する研究が開始された。諏訪湖のアオコ毒素microcystinの消長については,1991年から1998年まで8年間に及ぶ長期観測が行われた。その結果,Microcystisのアオコ形成初期に見られる細胞の増殖期には細胞内microcystin濃度が高いが,アオコの衰退時には細胞外microcystinの濃度が高いことが分かった。このようにアオコの衰退時期にはMicrocystisの細胞は分解が進み,細胞からmicrocystinが溶出することにより湖水濾液中のmicrocystinの割合が高くなる。諏訪湖産の淡水二枚貝,イシガイ(Unio douglasiae),ドブガイ(Anodonta woodiana),カラスガイ(Cristaria plicata)はmicrocystinを蓄積することが分かった。特に,毒素の含有量が多いイシガイについて,部位別のmicrocystin含有率を示すと,中腸腺が53%,鰓と筋肉が34%,生殖腺が6%,消化管7%となり,microcystinの多くは貝の肝臓に当たる中腸腺に蓄積されていることが明らかにされた。諏訪湖の二枚貝における中腸腺のmicrocystin最大蓄積量はイシガイが420μg g-1,カラスガイが297μg g-1,ドブガイが12.6μg g-1で,最大含有量は貝の種類により大きな差が見られた。また,朴らは諏訪湖からmicrocystin-RR,-YR,-LRを特異的に分解する新属新種のバクテリアを単離することに成功した。このバクテリアは20μgmL-1のmicrocystinを数日ですべて分解することができる。Microcystinの分解速度は分解時の温度に強く影響され,30℃で最も分解率が高いことを報告した。水源池になっている湖沼におけるアオコ毒素の存在は健康被害の危険性をはらんでいることから,浄水場には定期的なモニタリングのシステムを完備するなどの危機管理が必要である。また,microcystin分解バクテリアの動態を明らかにし,microcystin分解機構を詳細に解明するこができれば,水源池におけるアオコ毒素の処理に用いられる分解・除去方法に,その知見を応用することができると期待される。

諏訪湖の御神渡り記録に関する気候復元資料としての均質性

諏訪湖の御神渡り記録に関する気候復元資料としての均質性

13 諏訪湖周辺域におけるユスリカ成虫の飛翔行動

13 諏訪湖周辺域におけるユスリカ成虫の飛翔行動

Field Study on Acoustic Response of Chironomid Midges (Diptera: Chironomidae) Around a Hyper-Eutrophic Lake in Japan

A new method was developed to control adult chironomid midges, Chironomus plumosus (L.) and Einfeldia dissidens (Walker), using their acoustic responses to sound traps in the field. Trials were conducted in 1999 from 2 to 7 June (during emergence period of E. dissidens ) and from 2 to 7 September (emergence period of C. plumosus ) near hyper-eutrophic Lake Suwa in central Japan. Swarms of E. dissidens were formed at 1–3 m above the terrain and were observed from 1900 to 1930 hours. More than 97% of E. dissidens trapped from the swarms were males. In cylindrical sound traps, optimal trapping of swarming males occurred at a frequency of 240 Hz at 21.9 ± 2.3°C. Swarms of C. plumosus were formed at 1 m to >5 m above ground, and were observed from 1830 to 1900 hours. More than 88% of C. plumosus caught from the swarm were males, and optimal trapping of swarming males occurred at frequencies of 300–360 Hz at 20.7 ± 0.5°C. We compared our results with those of other chironomid species and attempted to clarify the relationship between female wing length and ambient air temperature. There was no correlation between the most attractive frequency and female wing length. However, a positive correlation existed between the most attractive frequency and air temperature. It is concluded that the most attractive frequency differed among species (interspecific) according to air temperature. These mechanisms may play an important role in isolation during chironomid swarming.

Massive flights of chironomid midges (Diptera) as nuisance insects and plans for their control in hyper-eutrophic Lake Suwa in Japan

(2000). Massive flights of chironomid midges (Diptera) as nuisance insects and plans for their control in hyper-eutrophic Lake Suwa in Japan. SIL Proceedings, 1922-2010: Vol. 27, No. 4, pp. 2378-2382.

The hydro-climatological significance of long-term ice records of Lake Suwa, Japan

(2000). The hydro-climatological significance of long-term ice records of Lake Suwa, Japan. SIL Proceedings, 1922-2010: Vol. 27, No. 5, pp. 2757-2760.

諏訪湖周辺における低層住宅の不同沈下調査事例による基礎の沈下抑制効果について

The region around Lake Suwa has a very soft layer and damage from differential settlement is apparent in many houses. In this study, the authors studies differential settlement at 28 built in Toyoda, Suwa City on the south side of Lake Suwa, Nagano. Prefecture over a period of five years from when the houses were newly built. Using the results of the study, the authors crganized the settlement pattern and the impect factors on settlement, and indicated a number of points that were discemed concerning on differential settlement of the low-rise housing. The research revealed that the depth of the banking have a great impact on differential settlement.

The efficiency of artificial wingbeat sounds for capturing midges in black light traps

AbstractThis study was conducted to develop a new method to control adult Chironomus plumosus (L.) midges (Diptera: Chironomidae) using their acoustic responses to sound + light traps in the field. Trials were conducted from June 10 to June 27, 1996 near the hyper‐eutrophic Lake Suwa in central Japan. In cylindrical sound traps, optimal trapping of swarming males occurred at frequencies of 270–300 Hz at 22.5 °C. This effect was significantly enhanced using a sound trap equipped with a black light lamp. The mean number of midges captured by sound + light trap was about 4.5 times the number of midges caught by either light or sound trap alone. In conclusion, the application of audio‐frequency sounds combined with attraction to light for chironomid midge control seems to be quite feasible, assuming the availability of a suitable collecting device.