ISSN:0020-9309    

DOI:10.1002/iroh.19850700402

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractFrom 1975 to 1981, 136 diurnal values ofP/Bcoefficients for the phytoplankton over the water‐column and 22 seasonal ones were obtained in 8 shallow fertilized lakes. A distinct direct correlation was found between the specific rate of photosynthesis and the temperature during the summer‐autumn season. In spring, the correlation was not so distinct; this period is characterized by higher photosynthetic activity of the phytoplankton due to a number of conditions favouring the development of algae: enrichment of water with nutrients, high daylight factor, and low biomasses in young populations of algae. An inverse correlation was found between the specific rate of photosynthesis and the phytoplankton biomass. The data obtained show that the introduction of nitrogen‐phosphorus fertilizers into the lakes (in the absence of unfavourable factors) greatly increases the dailyP/Bcoefficients. The specific rate of photosynthesis and the morphometry of lakes were found to be correlated directly in small (up to 50 ha)

ISSN:0020-9309    

DOI:10.1002/iroh.19850700403

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractThe pikeperch populations inhabiting three distinct water areas of Lake Balaton differ in regard of growth. Due to stock depletion, pikeperch in the NE‐basin of the lake grew considerably faster than ten years ago. The annual rate of growth in length (von Bertalanffy'sK) varied between 0.09 and 0.19. The specific rate of growth in length (GL) ranged from 0.16 to 0.23 and that of growth in weight (GW) from 0.52 to 0.69. Length and age‐structures of the stocks differed significantly between different areas and years, but the overwhelming majority of the stocks consisted of age‐groups IV–V (98.2–99.3%). From NE to SW, the rates of survival were 34, 29 and 70%, respectively. These differences, and the differences in growth resulted in changes in the productive capacity of the stocks. The ratios of production and biomass were 59% (NE‐basin), 63% (central basin) and 39% (SW‐basin), respectively. The magnitudes of production varied inversely. The 50% retention lengths of the seine nets used in Lake Balaton were 35.0, 35.7 and 42.5 cm with weights of 572, 655 and 1019 g,

ISSN:0020-9309    

DOI:10.1002/iroh.19850700404

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractThe competition betweenBosmina coregoniandB. longirostriswas studied by culturing of mixed and isolated populations in lake water. While interaction was detectable between the two species, they were capable of coexisting for at least 124 days. The pattern of predominance was found to depend on initial frequencies. The ratio ofB. coregonitoB. longirostrisin the pelagic zone of a mesotrophic lake could be explained on the basis of competition between either species. Birth, death, and population growth rates proved to be delayed functions of stock density, as was borne out by cross‐correlation analysis of experimental population dynamics. Time lag estimates for all three rates varied for different phases of population oscillation. For accurate assessment of time lags, the phases of monotonous changes in density should have been separated from one another. The time lag estimated for the rate of population growth in mixed cultures was significantly higher for the superior competitor (B. coregoni). This estimate may well be predicted as an arithmetic mean value cf time lag estimates for birth and death rates. The duration of population growth (or decline) was correlated to the time lag of the death rate, whereas the amplitude was not correlated to any time lag at al

ISSN:0020-9309    

DOI:10.1002/iroh.19850700405

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractMost investigations dealing with rotifer reproduction have been performed with populations and not with individuals. At the same time the variations in the growth and reproduction rates of rotifers are of considerable interest. This paper presents the results of investigations carried out by culturing individuals ofPhilodina roseoladuring the lifespan of an individual under different temperature conditions ranging from 9 to 35 °C. The paper presents curves showing the growth in length and weight, the periods of maximum growth rate and the maximum sizes ofPhilodinaas affected by temperature conditions. The reproduction rate is investigated at the same time. The variation in egg evolution duration, in duration of the reproductive period and in the egg laying rate are shown under all the conditions investigated. The data serve as a basis for estimating the effect of temperature on the productivity ofPhilodina roseola

ISSN:0020-9309    

DOI:10.1002/iroh.19850700406

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractThe spring development of phytoplankton and the phosphorus content were monitored intensively in Laken Erken during the springs of 1979 and 1980. The dominant species were dinoflagellates, mainlyWoloszynskia ordinataandPeridinium aciculiferum, during the entire spring of 1979. The long period of ice‐cover (21 weeks) favoured the motile species, which were able to utilize the available light immediately below the ice. A considerable vertical migration was noticed in March 1979.These large and slow‐growing algae were able to store luxury phosphorus, and surplus phosphorus concentrations up to 12 μg P/l were measured, which corresponded to an algal content of 10 μg P/mg C. These values were more than twice as high as those recorded earlier in Lake Erken. Although a spring outburst of diatoms did not occur in 1979 and 1980, the algae were phosphorus‐limited in May, as indicated by high alkaline phosphatase activity, low algal surplus phosphorus content and high inorganic N : P

ISSN:0020-9309    

DOI:10.1002/iroh.19850700407

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractA technique for analyzing the stability of a zooplankton, phytoplankton, nutrient interaction model is described. This is an extension of a two‐dimensional predator‐prey model, incorporating a nutrient food source. In this study difference equations, rather than differential equations, are used to simulate the system since the systems are more easily studied in this formulation. Using only a few reasonable constraints on the system, a remarkable stability is obtai

ISSN:0020-9309    

DOI:10.1002/iroh.19850700408

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractPrimary productivity of the phytoplankton was evaluated by the14C and dissolved oxygen methods in December 1981 at the Barra Bonita Reservoir (São Paulo State, Brazil). The primary production varied between 0.17 to 14.51 mg C m−3h−1at 4 and 0 m depth, respectively. About 57 to 94% of the photosynthetic activity was due to phytoplankton>50 μm. The highest value of assimilation rate (3.36 mg C mg Chl−1h−1) was found in the surface water. Dissolved nutrient concentrations were very high and consisted mainly of nitrate. Light penetration was low, the aphotic zone accounting for about 90% of the water column. Enrichment with nitrate and phosphate showed that both N and P stimulated the production of biomass (chlorophylla), mainly due to the addition of phosphate. The enrichment experiment also indicated that phosphate addition has a significant stimulatory effect on the growth ofMelosirasp. The limiting effect of light penetration on photosynthetic activity is more severe than that of

ISSN:0020-9309    

DOI:10.1002/iroh.19850700409

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractThe spatial and temporal fluctuations of the phytopigment content, “potential” primary productivity and total biomass of the epipelic algae of the River Wye System were studied during June 1979 to May 1981. Chlorophyll‐aand productivity values showed a downstream increase, much less obvious for the total biomass. Phaeophytin‐avalues followed almost similar spatial and temporal fluctuations to those of chlorophyll‐a. High chlorophyll‐aproductivity and total biomass values were recorded during warmer months due to favourable environmental conditions for algal growth, but lower values during unfavourable winter and fl

ISSN:0020-9309    

DOI:10.1002/iroh.19850700410

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractA comprehensive study of phyto‐ and zooplankton and macrozoobenthic components in Lake Nainital showed that species richness was high for plankton and low for macrozoobenthos. The algal biomass was dominated by greens (54 %) and blue‐greens (31 %), the zooplankton population by copepods (84 %), and the macrozoobenthic community by aTubifex‐Chironomusassociation constituting≥95 % of the annual number of the macrobenthic invertebrates. Respiration (807.5g C m−2year−1) surpassed gross production (630.5 g C m−2year−1). The mean annual ratio between phyto‐ and zooplankton biomass is 3.3 and between phytoplankton and herbivores it is 4.6. If biomass is treated as a measure of crude production, the relationship among the three trophic levels suggests that herbivory is inefficient while carnivory is efficient, because part of the primary production remains unutilized by dominant herbivorous zooplankters, whereasMesocyclops leuckarti, the sole carnivore, feeds efficiently on rotifers and juveniles of other copepods. The low diversity of different biotic components and theP/Rratio of less than 1 perhaps suggest that the lake is passing through the stage of heterot

ISSN:0020-9309    

DOI:10.1002/iroh.19850700411

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY