摘要:

AbstractThe accumulation of natural radioisotopes by aquatic organisms and bottom sediments was studied in two small rivers, one uncontaminated and the other polluted by effluents of uranium ore mining and milling.Parabolic regressions between the water and uppermost sediment content of both uranium and total beta activity (corrected for40K content) is presented and demonstrates the water cumulative capacity of organically rich sediments. For226Ra no significant differences between sediments with different organic content were found. The226Ra content of bottom sediments is expressed as a power function of radium and calcium concentration in the water.In the given reaches, 53% and 85% of uranium and over 90% of226Ra and total beta activity (corrected for40K) was accumulated in the upper two centimetres of sediments and biomass of aquatic vegetation. Filamentous algae, plankton, aquatic bryophyta and macrophyta from the present and other published data showed rather higher cumulation capacities as compared with bottom sediments.

ISSN:0020-9309    

DOI:10.1002/iroh.19740590502

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

摘要:

AbstractThe choice of methods to be used for the enumeration of bacteria in sea water must depend on the objectives of the investigators. Comparisons of data based on different methods may be invalid. An operational definition is given for a colony‐generating unit (CGU) which, under some conditions,maybe a single viable bacterium. Such units can conveniently be enumerated by a modification of the “minimum probable number” method currently employed in aquatic bacteriology. Counts of “viable bacteria” (CGU) in surface sea water samples from the region of the North Pacific Gyre (28° N, 155°W) were estimated to range from 10,000 to 200,00

ISSN:0020-9309    

DOI:10.1002/iroh.19740590503

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

摘要:

AbstractAn air lift, operated by a diver‐boatman team and permitting rapid excision and automatic sieving of uniform portions of mud, sand, and fine to medium shell hash bottoms, is described. The apparatus can be deployed from a very small boat. It is inexpensive to make and to operate and has been used with great success at depths of not more than five meter

ISSN:0020-9309    

DOI:10.1002/iroh.19740590504

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

摘要:

AbstractAt the fish ponds under study the authors defined several types of plankton which have been frequently found during the season (April – October). These types are: Early‐spring maximum of phytoplankton, Depression of phytoplankton, Bloom ofAphanizomenon, Maximum of Chlorococcales.The periods of “depression” seem to be typical for the managed carp ponds in the spring. They are characterized by the low density of rapidly reproducing algal populations (e. g.Cryptomonas) and by the dense populations of large cladocerans of the genusDaphnia. Chlorophyll in phytoplankton is less than 5μg/l, transparency is higher than 2 meters.Periods of the spring depression may be followed by the maxima of eitherAphanizomenonor Chlorococcales, with concentrations of chlorophyll increasing to 100 μg/l and more. The change from the phase of “depression” to the “maximum of Chlorococcales” is accompanied by decrease in numbers ofDaphniaand increase in numbers of the small cladoceran species, but all the mechanisms responsible for the transition are not yet

ISSN:0020-9309    

DOI:10.1002/iroh.19740590505

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effects of photoperiod and light intensity on the reproduction of laboratory populations of three species inPleuroxusfrom different geographic origins were determined statistically. There were highly significant differences in the numbers of gamogenetic individuals produced between the populations at different photoperiods but not at different light intensities. More males than ephippial females appeared at long‐day photoperiods.Pleuroxus denticulatusstocks showed greater variation of gamogenetic response to photoperiod and geographic origin suggesting that local populations have evolved different reproductive patterns to meet the major environmental stresses of the regio

ISSN:0020-9309    

DOI:10.1002/iroh.19740590506

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

摘要:

AbstractA quantitative study was made of the littoral microcrustaceans in a bog pond and an acid marsh located on the Avalon Peninsula, Newfoundland, from May, 1972 to May, 1973. A total of 17 species of Cladocera and 7 species of Copepoda were found in La Manche Marsh, while 21 species of Cladocera and 5 species of Copepoda were collected in Round Pond. The maximum standing stocks were similar in the two localities. The dominant forms in the summer and fall in La Manche Marsh were Cladocera:Acantholeberis curvirostris, Biapertura intermedia, Chydorus sphaericus, andIlyocryptus spinifer.In the winter the copepod,Macrocyclops albidus, was dominant, whileCyclops varicans rubelluswas the most abundant species in the spring. Round Pond also was dominated by Cladocera in the summer and fall; namely,Acroperus alonoides, Alona rustica, Alonella excisa, Chydorus sphaericus, andSida crystallina.The copepods,Eucyclops agilisandMacrocyclops albidus, were dominant in the winter and early spring.

ISSN:0020-9309    

DOI:10.1002/iroh.19740590507

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to determine the composition of the benthic fauna near the mouth of Delaware Bay. One hundred and five species were collected and identified from 277 grab samples. A sediment sample was also collected at each of the stations. Faunal density was low with the number of individuals rarely exceeding 10/0.1 m2. Species were ranked according to number of individuals; the nine top species comprised 83.4% of the fauna. The top three species,Tellina agilis, Gemma gemma, andNucula proxima, comprised 65.2% of all the individuals collected. A high percentage of the species (41.9%) occurred in two samples or less. The six most frequently collected species were compared with six sediment classes based on weight percentage of siltclay.Protohaustorius wigleyiandTrichophoxus epistomuswere found mainly in less than 10% silt‐clay.Tellina agilisandAmpelisca verrilliwere transitional between the pure sand and mud facies.Nucula proximaandHeteromastus filiformiswere members of a high silt‐clay facies (25% silt‐clay). The relative dominance (redundancy) was not significantly different in any of the

ISSN:0020-9309    

DOI:10.1002/iroh.19740590508

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

摘要:

AbstractAs early as in 1888, NORDSTEDT published some information about the algal flora of Rotorua lakes, on the North Island of New Zealand. He studied samples from the lakes Rotomahana and Tarawera, and made some notes on the algae in Lake Taupo. Since then a number of minor contributions with additional information about the algal flora of the Rotorua district have been published. The present paper describes the composition of phytoplankton in nine of the lakes in Rotorua district, and in Lake Taupo. These are all monomictic soft water lakes. The plankton is fairly rich in desmids, quantitatively as well as qualitatively. The study is based on random sampling by the author in March, 1968.

ISSN:0020-9309    

DOI:10.1002/iroh.19740590509

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19740590510

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19740590511

出版商:Akademie Verlag, Berlin    

年代:1974

数据来源: WILEY