摘要:

AbstractToxicity ofMicrocystisblooms to warm‐blooded animals generated by microcystins has bew reported world wide. The ecological relevance of microcystin production for cyanobacteria remains unknown. The microcystin concentration inMicrocystisblooms occurring in the Bautzen reservoir Was investigated. The microcystin content of samples were determined by HPLC and ranged from undetectabel to 14.7 μg mg−1. Various chemical and physical parameters were monitored at the same time asMicrocystissampling, however, there was no correlation between these parameters and microcystin dynamics. The spatial distribution of microcystin in theMicrocystispopulation was investigated once and showed no difference between samples taken at five stations. The microcystin concentration in ihc cell free water from the reservoir was below the detection threshold (306 h100μm) in which the highest microcystin concentrations

ISSN:0020-9309    

DOI:10.1002/iroh.19960810402

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

摘要:

AbstractA pico sizedSynechococcusspecies isolated from Lake Balaton was studied in batch and continuous cultures. This picocyanobacterium had a pH optimum at 8.5 and a temperature optimum at 28‐30°C. TheIkvalue for growth was 52 μEinstein m−2S−1, the maximum growth rate 2.27 d−1, the half saturation Constant of growth 1.2 μg PO4‐P I−1and the minimal cell quota 1.74 nig P g dry weight−1. The dry weight of cells showed a minimum, the chlorophyll‐a/biomass ratio a maximum as a function of growth rate. Above the quota of 3.4 fg P Cell−1significant amounts of non‐reactive dissolved Pho

ISSN:0020-9309    

DOI:10.1002/iroh.19960810403

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

摘要:

AbstractMany factors have ken put forward to account for the development of nuisance phytoplankton blooms in coastal zones. Usually hydrological factors as temperature or salinity stratification and adequate nutrient and trace metal availability are held responsible for the phenomenon. The most frequent causative organisms for nuisance blooms are dinoflagellates, many of which have a dormant stage (resting cyst) in their life cycle. The role of the complex life‐strategies of these forms in initiating bloom formation is the focus of this study. Special attention is given to 25 different dinoflagellate resting cyst types isolated from recent German North Sea and Baltic Sea sediments, and their germination frequency under different environmental conditions. Also, the role of cyst resuspension in relationship to the timing, persistence and recurrence of dinoflagellate blooms is extensive discusse

ISSN:0020-9309    

DOI:10.1002/iroh.19960810404

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19960810405

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

摘要:

AbstractFloating chironomid pupal exuviae were collected every three months from January 1992 to April 1993 on the windward shore of three endoreic karstic lagoons varying in the mineralization of the water and the characteristics of the sediment.A total of 16 chironomid species were identified in the three lagoons studied. Species richness was rather similar in the lagoons, varying from 8 species in Lagoon Chica to 10 species in Lagoon Caja. The chironomid assemblage of Lagoon Caja seems to be determined by the vast cover of aquatic macro‐phytes (mainlyMyriophyllcim spicurum), a substrate widely preferred by the species of the subfamily Orthocladiinae. However, in Lagoon Chica with a similar cover ofM. spicurm, only one Orthocladi‐inae species was found with a low relative abundance. The higher salinity may have limited the colonization of more Orthocladiinae species.The chironomid assemblages of the lagoons Chica and Grande are largely determined by the high mineralization of the water, most of the resident species being widely recognized as halophilous or tolerant of a wide range of water mineralization, and by the concomitant high intensity and frequency of disturbance in the sediment. Continuous anoxia, sulphide production and the compact layer of salt precipitates in these lagoons appear to deplete the abundance of sedentary detritivorous‐phytophagous species, but allow a stronger representation of highly mobile facultative predatory taxa (e.g.Proclucliiis)which are more able to withstand this constantly stressed environment, as in the profundal benthos of eutrophic aquatic systems with long‐lasting periods of

ISSN:0020-9309    

DOI:10.1002/iroh.19960810409

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19960810407

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

摘要:

AbstractWater velocity acting at the upper edge of the case opening was measured at the locations of 1074 cased caddis larvae along a cross section of the Seebach near Lunz Biological Station (Lower Austria). In addition, Froude number, boundary Reynolds number, bottom shear stress and thickness of the viscous sublayer were measured at the center of contagious sampling squares of 30 × 30 cm over the same cross section. Measurements were made at monthly intervals from 2 November 1993 to 24 October 1994 using an impeller‐meter (Ott C2; propeller diameter = 30 mm) and a set of FST hemispheres. A total of 16 species was recorded withDrusus biguttatusPictet,Allogamus auricollisPictet andPotamophylax cingulatusStephens being most abundant. Maximum values of current velocity and hydraulic stress parameters (e.g. Froude numbers up to 0.90) were recorded forD. biguttatus. P. cingulatusandGlossosoma conformisNeboiss, whereas lowest values of hydraulic stress parameters were observed inSericostoma flavicorneSchneider. In addition, up to 40% of the population in Drusinae species andP. cingulatuswas over‐represented in high stress areas at the streambed, whilst up to 36% of the population inS. flavicorneandAllogamusspp. were over‐represented in low stress

ISSN:0020-9309    

DOI:10.1002/iroh.19960810408

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

摘要:

AbstractWhile different studies investigated effects of surface properties on the adhesion and population dynamics of marine sessile organisms (Balanidae, Bryozoa etc.), little is known about sedentary freshwater macroinvertebrates. Artificial substrates were used to investigate the effects of Aufwuchs on density and distribution of colonizing blackfly larvae and pupae. Although, settlement of blackfly larvae often is said to be impeded by Aufwuchs or siltation, they colonized both bare substrates and those on which a thick Aufwuchs cover had developed. Often no differences in density appeared on substrates exposed for less than 6‐9 d. Thus Aufwuchs apparently does not prevent initial settling of larvae. However, simuliid densities on Aufwuchs covered substrates declined after several more days of exposure, suggesting that surface properties may affect long‐term settlem

ISSN:0020-9309    

DOI:10.1002/iroh.19960810410

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

摘要:

AbstractMacrobenthic samples Were collected along 3 north‐south transects at 244‐1394 m depth across the Chatham Rise, eastern New Zealand, to examine the distribution of polychaete assemblages in the region of the Subtropical Convergence (STC). Two main assemblages were identified: at 244‐663 m depth occurring mainly on the crest of the Rise, and at 802‐1394 m on the slopes of the Rise. Community composition differed., however, between the northern and southern slopes of the Rise. The southern slope supported higher faunal densities and a greater proportion of surface deposit feeders. This latitudinal difference may reflect variability in organic flux across

ISSN:0020-9309    

DOI:10.1002/iroh.19960810411

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY

摘要:

AbstractTubifex tubifex(Müller, 1774) was found in the profundal of 23 Estonian lakes out of the 187 lakes where oligochaetes were met in the deeper zone: in 4 cases as the single tubificid species but usually together withPotamothrix hammoniensis(Michaelsen) dominating in almost all lakes.T. tubifexwas abundant and large in size in the profundal of a few lakes with mesotrophic features but scarce and dwarfish (if not lacking) in the common eutrophic ones. Observations in aquaria demonstrate that its occurrence in eutrophic lakes is not limited by the bacterial food. Some kind of competition withP. hammoniensiscan be supposed but no direct evidence exists. Recent colonization of the profundal of an eutrophic lake byT. tubifex, probably from the littoral of the same lake, was observed

ISSN:0020-9309    

DOI:10.1002/iroh.19960810412

出版商:Akademie Verlag, Berlin    

年代:1996

数据来源: WILEY