摘要:

SummaryA pneumatically‐operated sampler for collecting water samples at close intervals of depth in lakes is described. The sampler uses plastic disposable syringes and may be operated at various depths and at the mud‐water interface. Examples of results obtained with the sampler are gi

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00080.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryA buoyant net for catching young fish quantitatively is described, together with some results based on samples taken with this net.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00081.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryPhytoplankton counts and chemical/physical analyses were carried out twice weekly for 2^ years on samples taken from Plover Cove Reservoir, and a description of the variations in species composition and abundance is followed by an analysis of the effects of these environmental factors on algal growth, and their correlation with phytoplankton abundance. In addition, 24‐h surveys were carried out over a 1‐year period in an attempt to evaluate the seasonal, diurnal and vertical distribution patterns ofthe more abundant phytoplankters.Blue‐green algal blooms were greatest in winter 1967/68 and in autumn 1969; shoreline‐attached diatoms were prevalent in winter 1968/69 and winter 1969/70. The blue‐green algal blooms have been attributed to a high rate of phosphorus and nitrogen supply, and the occurrence of diatoms at such specific times to an increase in light penetration due to the paucity of phytoplankton at these times. Various well‐marked distribution patterns were seen, and the seasonal pattern in the case of Microcystis aeruginosa was shown to be closely correlated with fluctuations in certain chemical parameters, namely. ammonia‐N, nitrate‐N and phosphate concentrations. Predictions have been made concerning future trends in the algal community o

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00082.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryFrom April 1969 to December 1970, oxygen concentrations and other physical and chemical parameters were determined in the bottom water at five sites (depths 14, 12, 8, 5 and 3 m) in Esthwaite Water in the English Lake District. In winter the bottom water at all five sites was oxygenated; while in summer, conditions at the deeper sites became anaerobic and concentrations of sulphide, ammonia and carbon dioxide increased.During the same period, some benthic ciliated Protozoa were counted at the same five sites. The species considered were Loxodes magnus, L. striatus, Frontonia leucas, Spirostomum minus, S. teres, Stentor coeruleus, S. polymorphus and Caenomorpha medusula and populations were assessed as number of individuals per 01 ml of sediment. It was found that: (1) the most dense populations tended to be at the deeper sites; (2) population maxima generally occurred when the bottom water was oxygenated (except for C. medusula) and; (3) there was, over the 21 months, considerable irregularity in the size and timing of population maxima.In March‐April 1970, population densities of benthic ciliates, at the five sites, were measured in terms of individuals per cm2of lake bottom. Population densities decreased with decrease in site depth. The availability of food organisms, turbulence and sediment texture were considered as factors which might control this distributio

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00083.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummarySpecimens of Stenostomum which could be attributed to either S. anatirostrum or S. bryophilum, from Britain, Kenya and Poland have been described, and compared with published descriptions of similar material collected in Brazil and Finland. It is concluded that 5. bryophilum ought to be regarded as a synonym of S. anati‐rostrum. S. anatirostrum is a very variable species with a wide geographical distribution. It occurs in aquatic and damp terrestrial habitat

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00084.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryTwo species of Stenostomum, viz. S. glanduloswn Kepner and Carter and S. anops Nuttycombe and Waters, are recorded for the first time from Poland. Descriptions of the Polish material are given, and these are compared with published information on the structure of the species. A new sub‐species, viz. S. Corderoi Marcus s. sp. poznanensis s. sp. nov. is recorded from Poland, and fully described. Fealures which separate the new sub‐species from S. corderoi corderoi Marcus are lis

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00085.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryA new species of Stenostomum, viz. S. beryii sp. nov. is described from Kenya. It was recorded from a pool near Nairobi, in April and May. The new species resembles S. hemisphericum Nasonov.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00086.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryStenostomum arevaloi Gieysztor, S. glandulosum Kepner and Carter, S. leucops (Duges), S. pseudoacetabtihtm Nuttycombe and Waters, and S. unicolor Schmidt are reported from E. Africa. The various localities in which each of the species were found are listed. All the species are new records for this region except S. Leucops which was recorded by Bohmig (1897) from Lake Victoria at Bukoba, Uganda. Descriptions of the species, based on the E. African material, are given.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00087.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe seasonal variation in abundance of the phytopiankton 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.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00088.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryBehaviour of Brachycentrus americanus was observed in a simulated stream in the laboratory every 2 h for 7 days in January, and in Lawrence Creek, Wisconsin, every half hour for 2 days in May. In the field, animals, algae, and detritus in the drift were sampled every half hour with an 800‐μm and a 60‐μm mesh net.The primary mutually‐exclusive behavioural units were filtering, case building, and withdrawn when the larvae had their cases attached to the substrate, and crawling and holding when cases were not attached. Diel changes in behaviour were similar i n the laboratory and field. Almost 100% of the animals were filtering at night, whereas only about 60% were during day. Withdrawn, case building and unattached activities occurred more frequently during the day. While only 0‐5% of the laboratory animals were unattached during the day, in Lawrence Creek 10‐20% were unattached at that time and many moved across the substrate and grazed. Drifting, which was acyclic, did not correlate closely with the diurnal increase in unattached activity.Available drifting food in both nets increased markedly following rain. In the absence of rain, dry weight of detritus from the 800‐μm net increased at night. Changes i n timing and method of feeding are discussed relative to gut contents, morphological adaptations, and energy expenditure of B. americanus, and to foo

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1974.tb00089.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY