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The seasonal variation in abundance of the phytoplankton groups in the river Oshun before and immediately after the closure of the Asejire dam is described. The river was dominated by the Bacillariophyceae throughout the period before impoundment but soon after, the Volcocaceae and the Dinophyceae became preponderant at the lake although the diatoms remained dominant at the source. Also, the period of maximum abundance of the diatoms occurred 8 weeks before the other phytoplankton groups attained their maxima in the river. Correlation coefficient values enumerated by computer revealed the controlling effect of the discharge, transparency and nitrate nitrogen on phytoplankton development in the Oshun. [ABSTRACT FROM AUTHOR]

The seasonal and depth distribution of phytoplankton in Gull Lake, a moderately large, temperate, dimictic, recreational lake in southern Michigan, U.S.A., is described and discussed. Diatoms (Fragilaria crotonensis, Cyclotella michiganiana, Asterionella formosa, and Synedra acus) dominate the spring phytoplankton. Populations of cryptomonads, green flagellates, and non-bloom-forming blue-green algae (Chroococcus and Synechococcus) grow mainly in summer. Diatoms grew under the winter ice, and objections are lodged to the classic explanation of seasonal growth in temperate lakes, and to a recent hypothesis concerning the ‘paradox of the plankton’. Two raphe-bearing large diatom species were considered to be truly planktonic. A Synechococcus species was similar to that described previously only from Loch Leven. [ABSTRACT FROM AUTHOR]

The article presents a limnological study on the plankton communities of Amchitka Island, Alaska. The study was performed in 1967 and included the examination of over one hundred ponds and lakes on the island wherein sixteen were chosen for event-related studies. The ponds and lakes were examined for several qualities including water chemistry, suspended particulate matter, and bacterial populations. The study included the use of a Van Dorn water sampler and a Sedgewick Rafter Cell. Data from the three years examined showed different kinds of present phytoplanktons including Ochromonas, Melosira, and Dinobryon. An overview of the study is provided.

The present investigation of Ösbysjön, Djursholm, comprises a qualitative and quantitative phytoplankton analysis of samples taken continuously 3/VI 1957–30/VII 1958 plus some single samples from 1959 and I960. The methods agree with those used in my investigation of Görväln (WILLÉN 1959, p. 242). Ösbysjön is a shallow lake of pond character without any influx worth mentioning. The phytoplankton was characterized by chrysophytes: Dinobryon and several other genera during the greater part of the year. Cyanophytes, desmids and diatoms played a secondary role in the standing crop. During the winter of 1958 a considerable decrease in the content of oxygen was noted, and hydrogen sulphide was formed in the deeper layers. It was possible to follow the changes of the phytoplankton composition from the beginning of January, when sulphur bacteria and, to some extent, iron bacteria began their development, to April, when bacteriophytes, some chlorophytes and dinoflagellates dominated (Figs. 3 a-c). During May all bacteriophytes gradually disappeared (Fig. 4), and the lake plankton returned to normal algal composition. In connection with the break-up of the ice there was a decrease of the total volume of standing crop. Neither during spring nor during autumn were any peak volume values recorded. Besides the bacteriophytes there was a great development of cyanophytes (Oscillatoria spp.), chlorophytes and cryptophytes after the ice had disappeared. Peak volume values were noted in the beginning of July (Dinobryon spp.) and at the end of April (Chlamydomonas and Glenodinium spp.). In comparison with Görväln the standing crop was considerably lower. [ABSTRACT FROM AUTHOR]

The article presents information on the distribution of diatom flora, Bacillariophyceae on some littoral sediments of the Lake District, England. The distribution of the species depends upon the type of the lakes that are divided according to the chemistry of the littoral sediments. The species that are found in the lakes having both low nutritional status and pH are Achnanthes flexella and Frustulia rhomboides. Lakes with higher nutritional status contains species like Gyrosigma acuminatum and Navicula pupula. Besides, there are some species like Melosira varians and Melosira distans, that are not found in the region as it is outside their normal habitat range.

The article offers information on the phosphatase activity in lakes of differing degrees of eutrophication in Great Britain. A studies on freshwater micro-organisms are conducted in sixteen lakes of the English Lake District. Factors which have ben considered include the underwater light climate, phytoplankton populations, and hypolimnetic oxygen deficit. It is revealed that enzyme was a good indicator of biomass present and degree of eutrophication. The organism was found to possess enough levels of the enzyme than those found in other micro-organism.

This article presents a study which investigated the influence of physical and chemical conditions on the spatial and temporal distribution of the phytoplankton and of an epipelic algae community in Abbot's pond in England. The study noted a marked vertical stratification of phytoplankton species during thermally stratified conditions. It also found that the positions of various species is related to physical and chemical conditions in the water column and in some cases to motility. The effects of shelter on the limnology and algal biology of Abbot's pond are discussed, and the possible future development of the pond is outlined.

The article examines the changes in chemical composition and phytoplankton population of Cyclotella pseudostelligera Hustedt. It mentions that the numbers of the plankton diatom Cyclotella pseudostelligera were connected to the quantity of silica in solution which also had an effect on the prototype of valve ornamentation. Clonal cultures strengthened the theory that the latter and the silica-deficient forms bear a resemblance to Cyclotella woltereckii Hustedt. Several picture of the cells of Cyclotella woltereckii-type from Priest Pot plankton in England are provided in the article.

The article presents a study that estimated the population density of the non-motile colonial diatom Tabellaria flocculosa (Roth) Kütz. var. flocculosa on the vertical submerged shoots of Pharagmites communis Trin. and Schoenoplectus lacustris (L.) Palla. Samples were collected in three lakes in the English Lake District for periods up to four years. The study concludes that favorable growth conditions deter grazing, parasitism and wave action from having any effect on the population density. During low light and temperature, a high population density of T. flocculosa can be observed. A discussion of this phenomena and the influence of various factors on the periodicity of an attached diatom is presented.

The article discusses the relation of nutrient compounds and other physical and biological factors to the growth in numbers of Asterionella formosa and other plankton diatoms in the English Lake District. It was observed that light and temperature are both significant to the population growth of Asterionella, since the population increases in 1.5 to 24 degrees Celsius and decreases during the time of maximum illumination. Parasites may not directly cause the drop in Asterionella numbers, but their utilization of nutrients in lake waters affects the renewal of growth in these diatoms. It was also seen that the increase of Asterionella is affected most by silica concentration, followed by phosphate concentration.

A conference paper about the changes in the phytoplankton population of the River Thames at Reading, England is presented. The phytoplankton of the River Thames was studied weekly from May 1966 until May 1968. Findings showed a good correlation between the numbers of diatoms and the amount of molybdate reactive silica in the water, while the highest diatom density occurred with the lowest concentration of silica and, at this time, the silica concentration was very close to a limiting value.