Long-term retention of surgically implanted radio transmitters in pikeperch

Radio-tagged pikeperch Stizostedion lucioperca (55–74 cm L _T) were recaptured in a reservoir by anglers 52–55 months after tagging. A total of four fish were recaptured during the summer of 2001. These recaptures are remarkable because of the long period between tagging and recapture and because only one (of 15 potential) tagged pikeperch had been caught in the long period since tagging.     

Midsummer heat wave effects on lacustrine plankton: Variation of assemblage structure and fatty acid composition

The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002.     

Limnology of a hypertrophic reservoir storing wastewater effluent for agriculture at Kibbutz Na'an,Israel

The reservoir investigated collects domestic and agricultural effluents after primary and secondary treatment. Despite the high concentration of organic matter (mean BOD⁵ = 60 mg l^–1), the reservoir does not deteriorate to produce obnoxious, anaerobic conditions. During a one year period, dissolved oxygen levels fluctuated widely but presented a long term dynamic stability, based on diffusion from the air during the winter mixing and on algal — bacterial — zooplankton equilibrium during the summer stagnation. The system, rich in organic and inorganic nutrients exhibited a much higher self-regulatory cability, than would be expected from its extreme enrichment. A hypothesis is proposed to explain the dynamic equilibrium achieved under extremely hypertrophic conditions.Human Environmental Sciences Division, School of Applied Science and Technology     

Effect of rainstorms on heterotrophic bacterial activity in a hypertrophic African lake

Hartbeespoort Dam is a hypertrophic man-made lake which is located in the Transvaal Province of South Africa. This region has recently experienced its most severe drought of the century. However, on three occasions in the summer rainy seasons of 1984 and 1985, major rainfalls (> 50 mm) occurred which caused large inflows to the lake. Inflowing river water entered as a density current causing marked silting of the water. Within the epilimnion (0–10 m) prior to these rainfalls there was usually no variation of bacterial numbers with depth, but heterotrophic bacterial activity (glucose uptake) decreased with depth concomitant with primary production. With the increased river inflow bacterial numbers did not increase but bacterial activity at the bottom of the epilimnion (10 m) increased to as high as 2.7 µg C l^–1 h^–1 in January 1985, reversing the depth profile of bacterial activity within the epilimnion. This resulted in decreased glucose concentrations (K_t + S_n) and turnover times. Heterotrophic activity per cell increased by between 2.5 and 5 times. These data demonstrate that storm events are important phenomena causing short-term changes in the metabolic activity of planktonic heterotrophic bacteria in lakes.     

Relative importance of temporal and spatial heterogeneity in the zooplankton community of an artificial reservoir

Zooplankton samples were collected monthly at three stations in Ogochi Reservoir during 1980, and the temporal and horizontal variations in the density of dominant taxa were evaluated by a standard 2-way ANOVA with random effects. The analysis revealed that horizontal is greater than temporal variation in the warm water season (> 18 °C), whereas temporal variation is greater in the cold water season (< 18 °C). Horizontal heterogeneity of the zooplankton community found in the warm water season seems to be associated with differences in site-specific conditions.     

洈水水库鳡鱼(Elopichthys bambusa)生长规律的研究

本文对洈水水库鳡鱼的生长及其利用进行了分析研究,结果表明:1.该种鱼生长快,高速生长时间长,可连续5年每年生长6kg以上;2.雌、雄鱼体长与体重生长分别适合Von.Bertalanffy的生长公式:L=L_∞(1-e-k(t-t·))和W=W_∞(1-e-k(t-t·))~3;3.雌鱼体重生长速度快于雄鱼,体长生长无明显差别;4.建议大中型水体中的鳡鱼与其它鱼类群落体重之比控制在3—5％为宜。     

洈水水库鳡鱼(Elopichthys bambusa)生长规律的研究

本文对洈水水库鳡鱼的生长及其利用进行了分析研究,结果表明:1.该种鱼生长快,高速生长时间长,可连续5年每年生长6kg以上;2.雌、雄鱼体长与体重生长分别适合Von.Bertalanffy的生长公式:L=L_∞(1-e-k(t-t·))和W=W_∞(1-e-k(t-t·))~3;3.雌鱼体重生长速度快于雄鱼,体长生长无明显差别;4.建议大中型水体中的鳡鱼与其它鱼类群落体重之比控制在3—5％为宜。     

Distribution pattern of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in a reservoir

Horizontal distribution of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in the Ishitegawa Reservoir, Ehime Prefecture, Japan, was investigated. Water quality was also surveyed. It was observed that the population ofC. hirundinella exponentially decreased in number from the head of the reservoir to the dam site. Further investigation proved thatC. hirundinella initiated growth at the head of the reservoir, and later gradually expanded downstream. It was found during the period of increase in water temperature that the cell density ofC. hirundinella at the uppermost station exponentially increased.     

Succession of phytoplankton species in indoor reservoir models varying in sediment composition and water inlet site

Using four continuous-flow indoor reservoir models, the combined effects of varying water inlet depth and sediment composition on phytoplankton species composition and its succession pattern were studied. Species which are known to bloom in eutrophicated reservoirs were dominant in the species succession in each tank. At any one time, a step-like pattern was observed in the composition of the dominant species of each tank, wherein all the species which appeared in a tank with a lower phosphorus concentration were included in the species composition of the tank with a higher phosphorus concentration in an additive relationship.     

Seasonality,abundance, and biomass of bacteria in a southwestern reservoir

The seasonality, abundance, and biomass of planktonic bacteria was investigated in a south temperate zone reservoir. Epilimnetic samples were collected periodically throughout 1983 from 5 locations within Lake Arlington, TX. Total bacteria were determined from epifluorescence microscopy and averaged 1.1 × 10¹³ cells m^–3 of water. Planktobacteria accounted for 85% of total cell counts and 73% of total bacterial biomass. Cell volumes were substantially larger in winter than in summer and were negatively correlated with temperature. Cell volumes ranged from 0.076 to 0.330 µm³ and averaged 0.160 µm³. The average biovolume corresponded to a sphere 0.670 µm in diameter. Bacterial biomass was high, averaging 172 mg C m^–3 of water and reached seasonal maximum during winter months. Correlation analysis (simple linear and multiple linear) revealed that approximately 50% of the variation in bacterial biomass could be accounted for by variation in temperature and dissolved organic carbon.