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doi: 10.1007/BF00179536pmid: N/A
Summary Sixteen epifaunal species are identified encrusting dead valves of Mercenaria mercenaria, Mya arenaria, and Aequipecten irradians exposed for one year on the bottom of Buzzards Bay, Massachusetts. The three most common cheilostomatous bryozoans are Schizoporella unicormis, S. biaperta, and Parasmittina trispinosa. Balanus (Balanus) amphitrite neveus demonstrates a preferred orientation of the rostro-carinal axis parallel to the growth lines of Mercenaria mercenaria, Mya arenaria and Aequipecten irradians. No preference for difference bivalve shells is apparent in any of the epifauna examined. The lesser abundance of most species on Mercenaria mercenaria valves may be due to the more rapid burial of these heavier valves in shifting sediments of the study area.
doi: 10.1007/BF00179537pmid: N/A
Summary 35 samples from different habitats but under the same environmental conditions have been analysed and compared with each other. The non-planktonic flora was found to be more varied than the phytoplankton, species of which remained more or less constant irrespective of the sampling area. Diatoms dominated the plankton, while in the other habitats most of the algal groups were well represented, although this depended, to a great extent, on the nature of the substratum.
doi: 10.1007/BF00179538pmid: N/A
Summary Seasonal abundance and the pattern of fluctuations in the zooplankton of a tropical fish pond has been studied at weekly intervals for a period of two years from September 1960 to August 1962. Except for a group of ciliates, protozoa were found only in limited numbers. Coleps, Tintinnus and Difflugia were recorded during both the years, whereas Arcella and Codonella were collected in the first year only. Other members as Centropyxis, Didinium, Paradileptus, Stentor and Bursaria were seen occasionally as few individuals. The total numbers of protozoa showed their peak from January to April and the prevailing phytoplankton abundance and temperature conditions are suggested as probable causative factors. More than thirty species of rotifers were recorded during this study, although many of them were only in limited numbers. Loricate forms showed their maximum density in summer months only, when total alkalinity values were also high. Nonloricate forms were found during September, October and December to February. The effect of temperature, total alkalinity and phytoplankton on these populations have been discussed. Five species of Copepoda were recorded. The most dominant copepod Mesocyclops hyalinus was present almost throughout the year and its fluctuation pattern closely resembled that of the copepodids and the nauplii. Definite peaks in naupliar populations were probably indicative of periods of active reproduction. Among the five species of cladocera, Diaphanosoma brachyurum was present during certain months only, in both the years. Moina brachiata was present during the first year only. The total abundance of these microcrustacea showed direct relationship with phytoplankton production. The importance of these investigations in fish cultural practices is suggested.
doi: 10.1007/BF00179539pmid: N/A
Summary The alkalinity and pH of lakes (pans) in Central Africa on Kalahari Sand, varies with the physical nature of the pan. Natural pans show a range of pH from 6.1 to 8.7, and of total alkalinity from 10 mg/l to 580 mg/l. This range is attributable to local soil differences. Some pans have been deepened or have had water pumped into them to provide drinking points for game animals. The alkalinity of “pumped” pans is determined by the alkalinity of the water pumped into the pan and the time during which this has taken place. All these types of pan show cyclic seasonal variation in alkalinity and pH. The range in these factors is similar from one year to the next. Animals living either in permanent (deepened or pumped) pans or in temporary (natural) pans have to withstand a wide range of alkalinity fluctuation in the course of the year.
doi: 10.1007/BF00179540pmid: N/A
Summary From the above one can infer that: 1. Living cells of Microcystis aeruginosa in which the blue-violet pigment was not yet discharged, had during 21 days no toxic effects upon Daphnia longispina, increasing in some way their surviving ability with no checking influence upon their reproduction. 2. The blue-violet pigment yielded by Microcystis through refrigeration and defrosting processes, had a toxic influence upon Daphnia longispina and Eucypris virens, this influence being more intense after a longer period of refrigeration of Microcystis and growing with the degree of its concentration. 3. Individuals of Eucypris virens were especially sensible to toxic effects of blue-violet pigment of Microcystis aeruginosa, obtained through refrigeration. The toxical influence of cell liquor of Microcystis upon Daphnia and Eucypris may explain the often observed fact, why a mass development of some algae in some lake zones is not accompanied by a corresponding animal plankton life.
doi: 10.1007/BF00179541pmid: N/A
Summary 1. In some stages of their development the algae Spirogyra sp. and Euglena viridis contain in their cells bacteriostatic substances that have a reducing influence upon the growth of Sphaerotilus natans, Bacillus mycoides and Leptothrix ochracea. The extract of these algae were found to have no bacteriostatic effect upon Escherichia coli, Sarcina lutea and Staphylococcus aureus. 2. In relation to all above mentioned bacteria species on Agar plates, during our testing the extracts from Cladosphora glomerata, Zygnema sp., Chlamydomonas sp., Stratonostoc gelatinosum, Anabaena sp., Oscillatoria sp., Aphanizomenon flos aquae and Microcystis sp., no bacteriostatic effects could ever be detected. 3. Extract from Lemna minor had bacteriostatic effect in relation to Sphaerotilus natans. 4. Bacteriostatic effect of algal cell \3- contents appeared in some unprecised stages of their growth in the pond \3- possibly in some connection with its properties. 5. In general, the activity of an extract from cell contents of the algae was quickly lost in indoor conditions. When the extract was preserved at −4°C its bacteriostatic activity, was often pronouncedly enhanced and in the case of Spirogyra also prolonged in time to as much as 6 months. 6. Extract from Euglena viridis maintained its activity when, pasteurized at 60\dgC, 70\dgC and 80\dgC. In this latter case the extract was sterile. 7. Bacteriostatic effect of Lemna minor extract disappeared in the refrigerator within 5 days. 8. Cell extract from Microcystis, obtained by refrigeration and defrosting (cell juice blue-violet in colour) which was poisonous to Daphnia longispina and Eucypris virens, did, not reduce the growth of bacteria on Agar plates.
Dumont, Henri J.;de Coninck, L.
doi: 10.1007/BF00179542pmid: N/A
Summary A study is made of the vertical migrations of several zooplankters in a recent artificial freshwater reservoir in the lower part of Belgium. Two series of cyclical observations were made, the first one during summer stagnation (30 hours), the second one during autumn overturn (48 hours). In both cases numerous plankton collections were made at different depths and a number of physico-chemical features of the water, suspected to show a diurnal rhythm too, were determined (temperature, O2, pH, HCO sup−inf3 ). Using the statistical technique basically developed by Ricker, significant vertical migrations were found during the stratification period and for every species that was taken into consideration. During overturn, vertical migrations were much less evident and in some cases even doubtful. The causality of this phenomenon is briefly discussed.
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