摘要:

AbstractA survey of ecosystem research in brackish coastal waters (Baltic Sea) by the Department of Biology, University Rostock (GDR) is given. Using selected results the main goals are demonstrated, outgoing from the first steps initiated by W. Schnese.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750102

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractAlona diaphana, a common littoral tropicopolitan cladoceran, occurs in the limnetic of two Ethiopian lakes in considerable numbers and over long periods of time. Our results are presented and the composition of limnetic and littoral zooplankton, in terms of previous records of such incursions, are discussed. The high persistent densities ofA. diaphanaare due to the extensive littoral areas in the lakes, where it originates, the high intrinsic rates of increase of this species, the low diversity of zooplankton, reducing competition and the low level of predation.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750103

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractDensities of bacterioplankton and phytoplankton were studied in relation to water retention time, temperature, nutrient concentrations, and other variables in a eutrophic montane reservoir (Bluestone Lake, West Virginia, U.S.A.). Weak temperature stratification occurred occasionally during the summer, but the reservoir did not become anaerobic. Water retention times were short (3.9 to 9.7 days between June and December), and differences in flushing rate within that range were important in regulating phytoplankton populations. Green algae and planktonic diatoms were dominant in summer during periods when water residence times were shorter. The occurrence of blue‐green algal blooms in fall was related to increased water residence times. Retention time was highly correlated with the percent composition of phytoplankton represented byAnabaenaspp. andMicrocystissp. (r=0.898,p<0.001). Advective effects limited phytoplankton biomass when retention time was shortest, but were not as important when retention times were longer. Peaks in bacterial densities often coincided with decreases in viable algal cell densities, so bacterioplankton were less directly related to retention tim

ISSN:0020-9309    

DOI:10.1002/iroh.19900750104

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractThe colonization byChironomusspp. of two ponds filled after a dry period was investigated. Field data were collected by means of quantitative benthic samples and emergence traps.C. melanescens. C. annularius, C. riparius, C. piger, C. luridus, C. obtusidens, C. plumosus, C. dorsalisandCamptochironomus tentanswere determined cytotaxonomically in ponds investigated.C. melanescensandC. annulariusappear to be the most characteristic species colonizing in high numbers in newly filled ponds. Larvae ofC. annulariusgrew more slowly in ponds compared with the former one which resulted in a characteristic succession of both larval types. Most species mentioned disappeared completely from the ponds investigated after the metamorphosis of a single cohort. They were replaced byC. plumosuswhich was often attended byC. annulariusin smaller ponds.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750105

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractThe P‐budget of Dal Lake in Kashmir is described for a 12 month period. The lake is characterized by high P‐loading (7.5 g · m−2a−1) and had high P‐retention (retention coefficient 0.32). P‐loading in the lake showed positive and negative relations with flushing rate and P‐retention respectively. A negative relation was similarly found existing between flushing and P‐retention. The roles of various biotic and abiotic factors in the P‐budget of the

ISSN:0020-9309    

DOI:10.1002/iroh.19900750106

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractSeasonal content of total soluble carbohydrate, total soluble protein, free fatty acids and alkaloids were examined in a population ofCeratophyllum demersumgrowing in a pond on the southwestern edge of the Canadian Shield. Total soluble carbohydrate and total soluble protein were inversely correlated. Free fatty acids were dominated by (16:0 + 16:1), 18:2 and 18:3. Relative proportions of the different free fatty acids remained roughly constant throughout the season. Alkaloid concentrations showed large fluctuations, with the highest values found during the first half of the season. Carbohydrate and protein contents of associated periphyton were not correlated with host macrophyte metabolism.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750107

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractThe aim of this report has been to present results concerning analytical quality controls of Hg analysis of fish and sediment, analyses of Fe, Ca, total‐P, K, pH, alkalinity, conductivity, colour and hardness (Ca + Mg) of lake water samples. Despite the fact that these are standard parameters in many regular water control programs, there are major differences in the reliability with which these parameters can be determined. The focus here is on an overall inter‐laboratory comparison between the parameters. Six laboratories have been involved in the analysis. Selected results: pH gives the lowest (average) relative standard deviation (error), about 2 %; conductivity gives an error of about 5–7 %; alkalinity yields an average error of as much as 13–25 %, which is the largest among the parameters studied here; colour also gives a high error, 9–15 %; hardness gives a relative standard deviation of about 6–7 %. Of the other parameters (i. e., Hg, Fe, Ca and P), Hg gives the best reliability and Fe and P the lowest. To have knowledge of the reliability of the analytical data is of paramount importance in most control programs and resear

ISSN:0020-9309    

DOI:10.1002/iroh.19900750108

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractThe ingestion of mineral particles byBiomphalaria glabratais proved and the importance of these particles in the diet of the snails is investigated. The number of particles ingested rises with the size of the snails and they are retained in quantity in the alimentary tract when an adequate supply is not provided. The size of grit found in the gut differs widely from the mixture offered. Mineral particles are ingested actively and selectively.Quantitative investigations comparing snails cultured with and without sand showed a slight advantage concerning growth and reproduction for snails cultured with sand.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750109

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19900750110

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19900750111

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY