摘要:

AbstractEvents in the plankton community of a 120 ha, shallow (1.2 m), brackish lake have been studied with the help of two watertight enclosures, each of which isolated about 300 m3of water and its underlying sediment. Analyses of soluble reactive phosphorus, total phosphorus, ammonia‐N, nitrate‐N, silicate‐Si, chloride, photosynthetic pigments, phytoplankton and zooplankton counts are reported and are related to inputs of nitrogen and phosphorus into the lake from adjoining basins and the catchment, and to the hydrologic regime. The inputs of phosphorus are budgeted and a very large roost of black‐headed gulls appears to provide most of the phosphorus supply. The results are discussed with reference to the eutrophication of the lake and decline of aquatic macrophytes which have occurred in the past te

ISSN:0020-9309    

DOI:10.1002/iroh.19780630302

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractThe salinity of Saskatchewan saline lakes varies up to 342%0. Highly saline lakes are widely distributed. Some reach saturation at high summer temperatures but salt precipitation occurs on cooling. Saline lakes tend to increase in salinity with time but the greatest changes occur in the shallow more saline lakes.The lakes are dominated by sodium, magnesium and sulphate. The cation sequences are dominated by sodium or magnesium while calcium and potassium are proportionally much smaller. Chloride or bicarbonate‐carbonate are secondary to sulphate among the anions. Ion sequences tend to be characteristic of certain physiographic regions. Lake types were magnesium (sodium) sulphate, sodium sulphate and sodium (magnesium) sulphate in order of abundance of lakes.Phosphorus and ammonia were high in concentration but nitrate and silica were scarce. The lakes were all alkaline between pH 7.8 and 9.8.The evolution of closed saline lakes is briefly discusse

ISSN:0020-9309    

DOI:10.1002/iroh.19780630303

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractPrimary production by phytoplankton, efficiency of photosynthesis, and chlorophyll‐aconcentrations were determined for seven saline lakes that varied widely in ionic concentration and composition. The investigations were done during the summer months of 1972 and 1973. Productivity ranged from 0.001 to 11.135 g C m−3day−1and 0.053 to 7.968 g C m−2day−1. Highest productivities were measured in two lakes that supported blooms ofAphanizomenon flos‐aquaeandNodularia spumigena, respectively. Species of Cyanophyceae, Bacillariophyceae and Chlorophyceae dominated the phytoplankton of the study lakes. Active chlorophyll‐aranged from 0.01 to 116 mg m−3. Integral photosynthetic efficiency estimates were<1% except during phytoplankton blooms when they were considerably higher. The overall range of 0.03 to 3.8% is concordant with estimates for other lacustrine ecosystems. The extinction of light caused by photo‐synthetic processes, orin situefficiency, was<1% in the trophogenic zone for most lakes but, it was considerably higher during blooms.In situefficiencies invariably increased with d

ISSN:0020-9309    

DOI:10.1002/iroh.19780630304

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractIn laboratory models of sewage ponds operated on a semicontinuous‐flow basis, the net primary productionIIof the phytoplankton was measured by harvesting the suspended matter both from the outflow and the bottom of the vessels at daily intervals. The maximum value ofIIwas as high as 50 mg dry weight/l day (corresponding to 20 mg C/l day). With the nutrient loadLkept ad a constant level, the steady state phytoplankton biomassxdecreased with decreasing water residence timetin accordance with the dropping inflow concentration of the nutrients. On the other hand, at 20 °C no higherxwas yielded att=40 than att=5 days. This result obviously has to be attributed to a substantial increase in grazing rate with progressingtat the temperature level of 20 and 30 °C. In this connection extremely low magnitudes ofIImay result despite optimum levels of nutrient supply, radiation and temperature.The highest estimates ofIIhitherto measured and recorded in the literature relate to the euphotic zone depth (zeuin m) as foll

ISSN:0020-9309    

DOI:10.1002/iroh.19780630305

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractDiatoms were examined in surface sediments collected from 43 lakes throughout New York State to determine the interrelationships among the abundances of various diatom taxa,' lake productivity and lake morphometry. Diatom ratios, including the A/C, C/P and five new quotients, were not well correlated with lake productivity, probably because of the diversity of the taxa which they employ. The abundance of individual genera or combinations of genera were better indicators of productivity. Cyclotella was the best single indicator of productivity being most abundant in low productivity lakes. Several fairly distinct diatom associations were identified by correlations between all possible pairs of diatom taxa. Finally, lake productivity was found to be significantly correlated with morphometry, being highest in small/shallow lakes.

ISSN:0020-9309    

DOI:10.1002/iroh.19780630306

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractThe limnetic crustaceans of Grasmere, a small lake in the English Lake District, were studied from February 1969 to December 1970 (23 months) and from January to December 1975. These observations were made before and after a change in sewage effluent treatment effected in May 1971. Planktonic species, except for one cladoceran, were more abundant in the second than the first period, while hypolimnetic and profundal forms either became less abundant or modified their life‐style in conjunction with a developing hypolimnetic oxygen‐defi

ISSN:0020-9309    

DOI:10.1002/iroh.19780630307

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractPreservation in 70% ethanol or 4% formaldehyde solution resulted in the leaching of ca. 30% arid ca. 10% dry matter, respectively. Subsequent soaking in water considerably increased leaching. The percent ratio of dry weight to live weight decreased during the summer from ca. 15% in June to ca. 11 % in September for the fourth instar larvae. The results indicate that formaldehyde can chemically react with the larvae, thereby increasing their dry weight. The dry weight of the gut content was ca. 4% of the total dry weight.

ISSN:0020-9309    

DOI:10.1002/iroh.19780630308

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractNo severe changes take place in the plankton of highly eutrophic non‐stratified water bodies up to a stocking rate of 1,000 Si3/ha. This rate gives additional yield of 200‐300 kg/ha. Stocking rates of 10,000 Si3/ha allow selective overexploitation of microphytoplankton incl. bluegreens and of nearly all zooplankton. Yield reaches in this case 1 t/ha in 1 m deep wat

ISSN:0020-9309    

DOI:10.1002/iroh.19780630309

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

摘要:

AbstractThe paper describes the food ofClarias batrachus(LINN.) occuring in derelict and swampy waters of the Bihar region of the Indian subcontinent. The study revealed that the early post‐larval stage is exclusively planktophagous while in the late post‐larval stage it starts including larger organisms in its diet. Juvenile stage is predominantly insectivorous. Though adults have a wide range of food preference, the insect material forms by far the most important source of their food. The fish did not appear to possess enough sense to sort out edible from non‐edible forms. March and September are the peak periods of relatively intensive feeding. The intensity of feeding in relation to the size of the fish showed that the average weight of food/g weight of the fish decreases with increasing weight of the

ISSN:0020-9309    

DOI:10.1002/iroh.19780630310

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19780630311

出版商:Akademie Verlag, Berlin    

年代:1978

数据来源: WILEY