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We studied seasonal change in adult crane fly emergence from slow sand filter beds in an inland climate area of Japan and identified a total of 12 genera and 20 species belonging to two families. Crane fly fauna in filter beds was dominated by two species Antocha (Antocha) bifida and Antocha sp. 1. Emerging adults of the two main species showed a significant seasonal change in body size (determined by wing length), which decreased steadily from spring to summer and increased again in fall. We speculate that water temperatures influenced the decline in the wing length of crane flies on such filter beds.

The long-term population dynamics of chironomids were investigated in Lake Suwa, a shallow eutrophic lake in Central Japan, in order to clarify the temporal variations in the abundance of Propsilocerus akamusi (Tokunaga). The characteristics of the emergence of P. akamusi from the lake in recent years are (1) shorter emergence periods, (2) smaller number of midges collected, and (3) high ratio of females. These results clearly show that the number of D. akamusi in Lake Suwa has recently tended to decrease. There is significant relationship between the density of larvae in spring and the total number of midges trapped during the emergence period in fall. Thus, it is possible to estimate the focus of massive emergence of the midges from the larval density in the spring., Article, Medical Entomology and Zoology. 54(1):89-96 (2003)

Lake Suwa is a shallow eutrophic lake in central Japan. We have investigated the long-term population dynamics of chironomids in this lake. The objective of this study was threefold: (1) clarifying temporal variations in the emergence pattern of P. akamusi midges, (2) assessing dynamics in density, biomass and distribution pattern of Propsilocerus akamusi and Chironomus plumosus larvae in this lake, and (3) determining key factors that may affect these variations, as well as comparing the results of this study to those of previous reports. Emergence periods of P. akamusi midges from the lake have tended to become shorter in recent years. Furthermore, the mean daily catch of midges exhibits a clear decrease over time. In contrast, average densities of P. akamusi and C. plumosus larvae in the lake were 73.3±48.0 (SD) and 3.2±9.4 individuals per m2, respectively. Compared to 1986, this amounts to a decrease of about 1/70 and 1/130, respectively. Finally, the organic matter in the upper layer of the sediment has also been decreasing. This suggests that the basic conditions necessary for chironomid larvae habitats, especially quality and quantity of food, seem to be changing in Lake Suwa as water quality improves.

This is an experiment in which purifies the comparatively lower level of ionic lead by sand filtration pond model. Similarly, it also tried on zinc. As a continuation of previous work, the behavior of lead and zinc in a continuous-culture sand filtration pond model over 2 weeks were examined by dosing the influent with lead or zinc solutions. The sand filtration pond model was covered with a bath lid. It was found that most lead was adsorbed in the top about 8 cm of the sand columns with only 15% of the added load detected in the effluent, whereas zinc persisted throughout the columns and 78-90% of load was present in the effluent. Thus, sand columns exhibit a high capacity for the immobilization of lead. From a correlation between lead and particulate organic carbon in the sand columns, indicating that the adsorption of lead was principally caused by reaction involving organic substances and due to a relationship between the two materials. These results also highlight the dissimilar mobility of lead and zinc

This book provides a state-of-the-art assessment on a variety of biofiltration water treatment systems from studies conducted around the world. The authors collectively represent a perspective from 23 countries and include academics/researchers, biofiltration system users, designers, and manufacturers. Progress in Slow Sand and Alternative Biofiltration Processes !! Further Developments and Applications offers technical information and discussion to provide perspective on the biological and physical factors affecting the performance of slow sand filtration and biological filtration processes. Chapters have been submitted from the 5th International Slow Sand and Alternative Biological Filtration Conference, Nagoya, Japan in June 2014. ISBN: 9781780406381 (eBook) ISBN: 9781780406374 (Print)

Chironomid fauna in slow sand filter beds were investigated and compared with those at two different water filtration plants; one in southwestern Japan, i. e., the Sakishima Islands, and the other in a plateau area, i. e., Honshu Island. As a result, the midges were found to be dominated by three taxa, Cricotopus, Paratrichocladius rufiventris and Tanytarsus oyamai at two filtration plants in the center of Honshu Island. On the other hand, in the Sakishima Islands, the most abundant species was Polypedilum nubifer, which was also collected on Honshu Island. In addition, we recorded two chironomid species from the Sakishima Islands., Article, Medical Entomology and Zoology. 52(2):129-135 (2001)

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.

The research was carried out to appreciate a slow sand filtration treatment by an investigation of suspended matter distribution in sand beds.The chlorination treatment was given to sand beds. The core-sampler to take suspended matter was inserted in slow sand filter model beds during the filter operation. The following results were obtained.Normalized head loss value was increased at a chlorination treatment model than at a nonchlorination model (control model) after about 35 days of filter run. From the depth distribution of the suspended solid (SS), a model with chlorination treatment retained large amount of suspended matter than a model treated by non-chlorination. And suspended matter was mainly retained at the extremely thin layer at the sand column of a control model.Small animals increased in the upper sand layer of a control, but were not existed in a model chlorination treatment.Measurement of particles in filtered water by a particle counter were decreased at a control model accompany with filter run.

To clarify the role of waterfront vegetation for Chironomid midges and make it useful for control countermeasures, an investigation of the number of chironomid midges resting on each form of vegetation and how they use Phragmites australis was conducted on massively breeding Chironomus plumosus and Eifeldia dissidens. As a result, significant differences were observed in the number of resting chironomid midges according to the type of chironomid and vegetation. Chironomid midges rested on Melilotus alba with the highest density. As for C. plumosus, many chironomid midges tended to rest on plants which had many leaves per unit stem length. About 70% of chironomid midges which flew to P. australis stuck to the leaves. The difference in numbers was not significant for either side of the leaves. In light of the above, the fact that such varied forms of vegetation exist in the shoreline area would mean that the chironomid midges may avail themselves of all kinds of resting places of the kind. In addition, it was thought that were a larger vegetation area to be secured along a lake waterfront, these midges could effectively provide a buffer zone between human living space and their own habitats.

Natural field survey was done to clarify the characteristic environment for a filamentous diatom Melosira to dominate in a slow sand filter. Four natural fields where Melosira was dominated in early spring were observed periodically. There were the basin of Shiraito waterfall at the foot of Mt. Asama, a natural pond of Sato Ike at the foot of Mt. Asama, pools in a dry river bed of River Chikuma where is a lower reach of sewerage plant and a hydroelectric power plant, a small downstream of Karasawa fall, and Soehi stream of a mountain small stream with slow water current as a contrast place where was not observed Melosira. The places where Melosira was observed at always in a year were a basin of Shiraito fall and pools in a dry river bed of River Chikuma. The basin was periodically cleaned to keep a clean basin. The pools were flushed out after the heavy rain and irregularly water discharge from the power plant. Both place are similar to a slow sand filter basin where the surface mud is scraped periodically. Small stream of Karasawa fall was hidden in the grass in summer. There was sometimes a evening shower in the mountain area and there was a sudden high water after a shower. In the pond Sato Ike, filamentous diatom was observed during the low water temperature period from fall tospring. However a filamentous green alga was dominated in summer. Filamentous diatom was apioneer plant in a stable environment with a slow water current and it was replaced tofilamentous green algae in warm period. The cause of this succession was discussed with the grazing activity of aquatic insect larvae.

(1997). Longitudinal distribution of plankton in a shallow reservoir of Broa in Brazil. SIL Proceedings, 1922-2010: Vol. 26, No. 2, pp. 553-557.

Heavy algal mat of a filamentous diatom is sometimes observed in an open slow sand filter. Amount of particle leakage breaking through a slow sand filter was measured as an indicator of chlorophyll α concentration in filtrate water during the filter run. Chlorophyll α concentration decreased rapidly since the beginning of filter operation. Chlorophyll α concentration after ll days of filter run reached to inconsiderable amount of 0.005 Chl. α mg m-3. This means the particle concentration breaking through the slow sand filter was negligibly small amount. Algal mat peeling during a continuous culture condition of filamentous diatom does not cause the particle leak through a slow sand filter.

Seasonal changes of developmental patterns of algal mats of slow sand filters (Someya water works, Ueda city, Wakata water works, Takasaki city and Nabeya-ueno, Nagoya city) were examined. The water sources of Someya water works and Wakata water works were a surface water of a stream and the water source of Nabeya-ueno was a reservoir water. In the cases of slow sand filters which water sources were stream water, an algal mat of filamentous diatom of Melosira grew well due to high nutrient concentration in raw water. It was remarkable in summer when there was high nutrient concentration. However in the case of a slow sand filter which water source was a reservoir water, the developmental rate of algal mat was extremely slow. The dominant species of algal flora on the algal mat on the filter bed were almost same as the flora in the inflow water from the reservoir. Algal mat on the filter bed was just accumulated with phytoplankton which was grown in the reservoir. The low growth rate of algal mat was due to lack of available phosphorus in the inflow water.

Removing dissolved nutrients from river water flowing into lakes and marshes is an effective method of preventing eutrophication of them. We have proposed the continuous cultivation of filamentous algae outdoors in artificial waterways to remove phosphorus and nitrogen from the water.The ability of filamentous algae to absorb dissolved nutrients depends on the radiation (illuminance on the water surface in the daytime, diurnal periodicity), the concentration of nutrient in raw water, the temperature, and the stream regime (flow velocity, shape of the substratum which the filamentous algae are attached to, water depth). This study investigated the effects of the diurnal periodicity on the ability of filamentous algae to absorb phosphorus and nitrogen.The results of field experiments in the artificial waterway have clearly confirmed that the ability of filamentous algae to absorb phosphorus and nitrogen is influenced by the diurnal periodicity of the radiation. The results indicated that in the case of river, lake, or marsh water in which the major constituents of inorganic nitrogen in the water are NO3-N, more dissolved orthophosphate is absorbed at night than during the day, and more inorganic nitrogen is absorbed during the day than at night.

This research was carried out to appreciate a slow sand filtration treatment by an investigation of suspended matter distribution in sand beds of Ishifune and Someya slow sand filters. The core-sampler was inserted to take suspended matter in slow sand filter beds during the filter operation when the filters were easy to clog in winter. The following results were obtained.From the depth distribution of the Total Organic Carbon, Someya slow sand filter detained larger amount of suspended matter than Ishifune slow sand filter. And suspended matter was detained until deeper layer of the sand column at Someya water works.The depth distribution of the Chl/SAND indicated the nearly same profile as TOC distribution.Pheophytin content in the sand column at Someya water works was several times larger at the deeper layer in the sand columns than Ishifune slow sand filter. From the depth distribution of the Chl/TOC ratio, Someya slow sand filter suggested that algae which had brought by inflow water at early times of filter run detained at the upper sand layer. Total cells number of the algae in the sand columns at Someya slow sand filter were from sevral to ten times higher than Ishifune slow sand filter.

The differences of algal mat development on the slow sand filter beds in shallow ponds (110 cm depth) and in deep ponds (171 cm depth) were studied at Wakata water works, Takasaki city. The algal mat development in shallow ponds was high growth rate and marked a high standing mass. This was remarkable in summer. Decrease of algal biomass was observed after the peak biomass on 10 days in shallow ponds. It was estimated that this decrease was caused by the grazing of Chironomidae larvae. Colony size of the length of filamentous diatom of Melosira was measured to evaluate the health condition of diatom. Empty shells and small numbers of cology were abundant in deep filter beds. And chlorophyll a content to total pigments of algal mat in shallow ponds was higher than that in deep ponds. It seems that active growth of filamentous diatom in a shallow filter pond keeps an aerobic condition in the filter bed.

This paper describes the vertical profile of adhered suspended matter on the filter sand and its composition in the upper column of a slow sand filter. The water source of the studied slow sand filter is a surface water of a stream. An active growth of algal mat of filamentous diatom and the floating algal mat peeled off from the bottom were commonly observed during the study period in summer. The upper sand column was taken when the supernatant water drained off for the filter cleaning after the long filter run.The majority of suspended matter was adhered on the filter sand in the upper 1cm of the sand column. The amount of adhered matter was quickly decreased with the depth. The order in the decreasing rate of suspended matter with the depth was: Chlorophyll a > Pheophytin a > Consumption of KMnO4 > Ignition loss > Mud (adhered suspended matter). These results show the biological degradation is active in the surface sand column. And almost all the suspended matters penetrated into the sand are easily trapped and are decomposed within the surface sand layer.

緩速ろ過池砂層内における抑留物質の深度分布を調査して、砂層内における抑留物質の浄化作用について評価した結果、以下のことが明らかになった。1) 懸濁物質は砂層上部の表層でほとんど捕捉されるが、砂層内に侵入した懸濁物質も砂層上層で抑留された。ろ過継続日数が通常の倍でも抑留物質の侵入度合は変わりがなかった。2) 砂層内での抑留物質の減少率は、クロロフィルa>フエオフイチンa>全有機炭素の順であった。このことから、抑留物質に対する分解能が物質によって異なることが考えられた。3) 藻類体の砂層内への侵入度合は、染屋浄水場よりも石舟浄水場の方が高かった。このことから、浄水場によってろ過池砂層内の懸濁物質の侵入程度が異なることが判明した。

AIM: This work is aimed at extending the understanding of urea cycle in freshwater ecosystems. Its degradation rate concerning microorganisms activities was measured in the turbid waters of Pindaré and Turiaçu rivers located on the pre-Amazonian floodplain, Brazil; METHODS: The Pindaré and Turiaçu aquatic systems have distinct dry and rainy periods. The investigation was developed in the middle of the rainy period, and field activities were carried out in the extensive water bodies from the middle to lower reaches. The rate of degradation in the surface waters of the two aquatic systems was determined with in situ simulation technique using 14C-labelled urea. Photosynthetic rates were determined by the radiocarbon technique simultaneously with experimental measurements of urea degradation rate; RESULTS: Urea degradation rates (sum of carbon incorporation into particulate matter and CO2 liberation into water) were 2.0 mg urea C m-3 day-1 in the Pindaré and 17.1 mg urea C m-3 day-1 in the Turiaçu waters. Daylight values were obviously higher than those in the dark, and the urea degradation rates in Turiaçu showed much higher values than those in Pindaré. Most of the urea degradation occurred during the CO2 liberation phase. The average of chlorophyll a specific urea degradation rate was 0.13 and 0.83 mg urea C mg chl.a-1 day-1 in both river waters. The ratio of urea carbon degradation to photosynthetic carbon assimilation in both waters averaged 1.2 and 4.2%, respectively. The residence time of urea in the surface water was calculated as 2.3 to 4.5 days in the Pindaré and 0.21 to 0.50 days in the Turiaçu. Much shorter residence times were obtained in the Turiaçu due to the high degradation rate of urea; CONCLUSION: The correlation coefficient between the urea degradation rate and chlorophyll a or photosynthetic rate showed a statistically significant value in the Turiaçu. This indicates that in the Turiaçu system the urea degradation rate was proportional to the standing crop of phytoplankton and their photosynthetic rate. A strong relationship between the urea carbon incorporation rate and photosynthetic rate in the light bottles was observed, indicating that the carbon incorporation into the phytoplankton cells was also related to the photosynthetic rate. The present brief residence time indicates that the urea was being rapidly recycled in the euphotic zone of the investigated systems in the rainy period. OBJETIVO: O objetivo deste trabalho é ampliar o conhecimento do ciclo da ureia em ecossistemas de água doce. A taxa de sua degradação em relação às atividades dos microorganismos foi medida nas águas turvas dos rios Pindaré e Turiaçu localizados na várzea pré-Amazônica, Baixada Maranhense, Brasil; MÉTODOS: Os sistemas aquáticos dos rios Pindaré e Turiaçu têm períodos diferentes de chuva e seca. A investigação foi realizada no meio do período chuvoso, e as atividades de campo foram feitas ao longo dos extensos corpos d'água compreendendo águas de médio a baixo cursos. A taxa de degradação nas águas superficiais nas respectivas estações de ambos os sistemas foi determinada com a técnica de simulação in situ usando 14C- ureia. As taxas fotossintéticas foram determinadas pela técnica de radio carbono simultaneamente com medidas experimentais de degradação; RESULTADOS: As taxas de degradação (somatório da incorporação de carbono na matéria particulada e liberação de CO2 na água) foram 2,0 mg de ureia C m-3 dia-1 nas águas do Pindaré e 17,1 mg ureia C m-3 dia-1 nas do Turiaçu. Os valores no claro foram naturalmente maiores que os obtidos no escuro, e as taxas de degradação no Turiaçu foram muito mais elevadas que as do Pindaré. A maior parte da degradação ocorreu durante a fase de liberação de CO2. As taxas de degradação específica de ureia da clorofila a foram calculadas com valor médio de 0,13 e 0,83 mg ureia C mg chl.a-1 dia-1 nas águas de ambos os rios. As taxas de degradação de ureia carbono para a assimilação fotossintética de carbono em ambas as águas foram em média 1,2 e 4,2%, respectivamente. O tempo de residência desse composto orgânico na superfície da água foi entre 2,3 a 4,5 dias no Pindaré e 0,21 a 0,50 dias no Turiaçu. Tempos de residência muito mais curtos foram achados nas águas do Turiaçu devido à elevada taxa de degradação; CONCLUSÃO: O coeficiente de correlação entre a taxa de degradação da ureia e a clorofila a ou a taxa fotossintética foi calculada como um valor estatisticamente significativo nas águas do Turiaçu. Isto indica que no sistema Turiaçu a taxa de degradação desse nutriente foi proporcional à quantidade de fitoplâncton e sua taxa fotossintética. Foi observada uma sólida relação entre a taxa de incorporação de ureia carbono e a taxa de fotossíntese nas garrafas no claro, indicando que a incorporação de carbono no fitoplâncton está relacionada com a taxa fotossintética. O breve tempo de residência indica que a ureia estava sendo rapidamente reciclada na zona eufótica dos sistemas investigados no período chuvoso.

When the bed resistance of slow sand filter increases, the schmutzdeck on the surface bed must be removed by scraping. The indication of the decision of this work is the increase of the head loss. However the head loss changes with the fil tering rate. The calculated head loss at the normal flow rate of 20cm/h is introduced as the normalized head loss which is popular in England. The normalized head loss at Someya water works in Ueda city, Nagano quickly increases in winter when the water temperature is low. In the growing season of filamentous algae, the normalized head loss does not increase.The algal mat is like as a blanket herb and it prevent the clogging of filter. The filter operations at several water works are compared with the data redrawn in normalized head loss.

A heavy filter clogging at a slow sand filter was observed in early July 1992. It was caused by the flow of phytoplankton (Nitzschia holsatica) from a reservoir.N.holsatica under the bloom condition consumed almost all available reactive phosphorus in surface water of the reservoir. And phosphorous concentration in raw water to the slow sand filter decreased in this period. A filamenlous diatom (Melosira varians) which prevented the filter clogging could not grow in the filter pond due to deficient of available phosphorus.

Role of filamentous alga ofMelosira varians which grows on the sand bed in slow sand filter is described and the lack of understanding of its continuous culture is discussed. Algal mat of filamentous algae is lifted by bubbles of oxygen produced by photosynthesis and the floating mat drains away through the over flow pipes together with adhering grains from the inflow water. Slow sand filter is an optimum environment for a continuous culture system of filamentous algae. The importance of the water level control of slow sand filter to drain the floating algal mat through the overflow pipe is discussed.

Massive flights of chironomid midges have been observed frequently, and they have caused some problems in the daily life of residents around water treatment works. The development of physical and biological control strategies against chironomid midges is urgently needed because chemical control is not feasible in slow sand filter beds. In this study, in order to collect basic biological data for controlling the massive flights of chironomid midges, seasonal changes in the abundance and species composition of chironomid midges and larvae were investigated in slow sand filter beds. We identified 21 genera and 49 species belonging to 3 subfamilies. In spring, Cricotopus sylvestris and Rheopelopia maculipennis were the dominant species, whereas Polypedilum nubifer, Cricotopus trifasciatus, Chironomus kiiensis, and Procladius sagitalis were dominant in summer. Tanytarsus mendax and T. volgensis were the dominant species in fall. Polypedilum nubifer, C. sylvestris, and C. kiiensis were the major pest species in Japan. The overall factors influencing the abundance pattern of chironomids supposedly are temperature and the quality and quantity of food in slow sand filter beds.

(1994). Primary production by harvest method in a pond of a slow sand filter. SIL Proceedings, 1922-2010: Vol. 25, No. 3, pp. 1996-1998.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:18:12Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:38:46Z : No. of bitstreams: 1 2-s2.0-0031465282.pdf: 741243 bytes, checksum: bc6f258f51befe39250db8c617f54a1d (MD5) Made available in DSpace on 2014-05-27T11:18:12Z (GMT). No. of bitstreams: 0 Previous issue date: 1997-03-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The Pantanal is one of the largest wetland in the world, and its located almost in the central part of South America. Preliminary studies on the chemical features of waters were carried out in July, 1983 in Rio Paraguai and its tributaries in southern Pantanal, and in January, 1986 for some lakes near Porto Jofre and a river in northern Pantanal. The former showed an extremely oligotrophic character and the latter a eutrophic character, while the nitrogen seemed to be the limiting nutrient rather than phosphorus in both waters. The oxygen deficiency in water seemed rather common throughout the area studied in spite of the difference in water temperature and the organic matter contents. Shinjuku 2-247, Meito-ku, Nagoya 465 School of Environmental Science University of Shiga Prefecture, Hikone 522 Elétronorte Centrais Electricas do N. do Brasil, CEP 70710, Brasilia, DF , Shimoshizu, Shinden 2535-6, Yotsukaido 284 CNPq, SEPN 507-Bloco B, 70740-901, Brasilia, DF Faculty of Education Kagawa University, Takamatsu 760 Dept. of Applied Biological Science Shinshu University at Ueda, Ueda 386 Niigata University, Niigata 950-21 Department of General Biology Federal University of Minas Gerais, CEP 30000, Belo Horizonte, MG Department of Zoology State Julio de Mesquita Filho Univ., CEP 18610, Botucatu, SP Department of Biological Sciences Federal University of Mato Grosso, CEP 78000, Cuiabá, MT Department of Zoology State Julio de Mesquita Filho Univ., CEP 18610, Botucatu, SP

A long-lived, heavy freshwater red tide of Pyridinium occurred in a newly built water supply reservoir, between late February and late May, 1972 and 1973, starting and spreading from the entrance region. The densities of the alga reached at least 9.3 x 104 cells per ml and at least 2, 700 μg chlorophyll- a per liter at a wind drift. The red tide is attributed to the increase of solar radiation, the hardness of water and the sewage drains from towns and croplands. The water mass containing a dense algal bloom was an excellent receiver of the solar radiation. This flagellate acted as an accumulater of nutrients at the entrance region of the reservoir.

Fluctuation of dissolved organic carbon (DOC) was studied during 1971–1972 at monthly intervals in surface layers of Sagami Bay. Concentration of DOC varied from 0.8 to 1.7 mgC/l in surface water (0 m). Maximum concentration of 1.7 mgC/l was observed in July 1971 and after then DOC decreased gradually to a minimum of 0.8 mgC/l in May 1972. The fluctuation of DOC during the observation periods seems to have close relations with those of water temperature and salinity. High DOC concentration found in summer months may be associated with bloom of phytoplankton or intrusion of seawater from Tokyo Bay and/or inland water containing high DOC.

The study on the freezing-out phenomena of lake water is carried out in two mountain lakes, Lake Suwa and Lake Haruna in the central part of Japan. The reduction rates were measured concerning the following components : dissolved oxygen, carbon dioxide, ions (Cl, Na, Mg, and Ca), dissolved organic carbon, particulate organic carbon and nitrogen, and bacterial number. Substances in solution in the waters freeze out to 80%. The freezing-out of dissolved oxygen and carbon dioxide was also observed. This may account for the significant accumulation of dissolved gases immediately under the ice at the distinct inverse stratification in Lake Suwa. This accumulation was not observed at a volcanic lake of Haruna. In Lake Suwa a trend of the decrease of concentration was observed in the ice from its upper layer to the bottom. In Lake Haruna the opposite tendency was observed. The viable number of bacteria reduces by factor 103 or more in freezing.

The distribution of chlorophylla and photosynthetic characterestics of phytoplankters were investigated along 155°W between 50°N and 15°S during the KH-69-4 cruise of the R. V. Hakuhō Maru (Aug. 12–Nov. 13, 1969). High concentrations of chlorophylla (more than 0.2 mg Chla/m3) were observed above the depths of 150 m at all stations except in 17°N, 5°S and 15°S. North of 20°N, the depths of chlorophyll accumulation shifted from near the surface to 50–100 m with southwards. In the equatorial region, chlorophyll accumulation centered at a depth of about 70 m and ranged vertically between 10 and 150 m. In all cases in the present study area, chlorophyll accumulation occurred within the euphotic zone (above the depth corresponding to 1% of the surface illumination), and except in the subarctic and some equatorial waters, this was usually prevalent in the lower half of the euphotic zone.

A filamentous diatom Melosira italica was collected at the beginning of rainy season from a shallow lake in the tropical savanna region in Brazil. Even the sample taken from surface water contained empty cells in high percentages. The number of cells per filament of M. italica showed a peculiar pulse-like frequency distribution with peak values at 4, 8, 12 and 16. Evidences of the synchronous cell division in this planktonic diatom under natural environment are discussed.