摘要:

AbstractIn situenclosure experiments were performed in a highly humic lake to examine the effects of acidification on phyto‐, bacterio‐ and zooplankton. The acidity of three enclosures was adjusted with H2SO4to pH 3.5, 4 and 5 and one enclosure and the lake served as controls. The diversity of plankton as well as the mean concentration of chlorophyll α, primary production and respiration of plankton decreased with increasing acidity. Bacterial density was slightly lower in the pH 3.5 enclosure than in the other enclosures and in the lake, but there were no differences in the morphological type or mean volume of the cells between different treatments. In the acidified enclosuresCryptomonas ovataandChlamydomonasspp. were the dominant phytoplankters, whileDinobryonandMallomonasspecies seemed to be most sensitive to acidity.Keratella cochlearis, Kellicottia longispinaandBosmina longispinawere the most tolerant zooplankton to aci

ISSN:0020-9309    

DOI:10.1002/iroh.19860710602

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractThe spring benthos of 22 lakes ranging from 1–88 gl−1salinity contained 58 species of macroinvertebrates, but only 23 species occurred in waters>3 gl−1. The amphipodHyalella aztecaand the chironomidsProcladius freemani, Chironomusnr.muratensisandCryptochironomusspp. were important at lower salinities (1–12 gl−1) whereas the chironomidsTanypus nubifer, Cricotopus ornatusandChironomusnr.annularisdominated at moderate salinities (5–30 gl−1) and dolichopodid and ephyrid dipterans were the only species in hypersaline lakes (>50 gl−1). Diversity decreased significantly with increased salinity.Mean dry biomass ranged from 0–9.12 gm−2, showing little correlation with salinity, though hyposaline lakes often had elevated values and hypersaline lakes very low values. Shallow lakes (<5 m) had significantly lower standing crops. There were long term changes in biomass (over 45 years) in some lakes due to cultural eutrophication or secular changes in salinity. Chironomids were by far the dominant contributors to biomass at salinities to 50 gl−1, above which dolichopodid and ephyrid dipterans dominated.The lakes were classified into four groups—subsaline, hyposaline, shallow hypo‐mesosaline and hypersaline, reflecting the importance of salinity and also relative depth as

ISSN:0020-9309    

DOI:10.1002/iroh.19860710603

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19860710604

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractBenthic studies were undertaken in two mangrove‐lagoons on the south coast of Cuba. Both lagoons are approximately 30–50 cm deep and the tidal range is 15–20 cm. There is little influx of fresh water, and the lagoons are normally euhaline. Most of the lagoon bottom is not colonized by plants, although filamentous algae (CladophoraandEnteromorphaspp.) andThalassia testudiumgrow in a few places. Meiobenthic organisms account for 92% of the invertebrates in the benthic zone of the lagoon. The five most common taxa (Nematoda, Copepoda, Tanaidacea, Oligochaeta, Polychaeta) account for 88–94% of the total number of individuals in Tolete Lagoon and in Basto Lagoon the five most common taxa (Nematoda, Copepoda, Ostracoda, Amphipoda, Polychaeta) account for 97–98%. Biomasses were 26.6 g/m2in Tolete and 20.2 g/m2in Basto Lagoon. The dominant taxon on the roots ofRhizophora mangleis Crustacea (Balanus eburneus, B. recurvusandCorophium insidiosum), accounting for over 60% of the total number of individuals. They are followed by molluscs (Crassostrea rhizophora)and the polychaetes (s

ISSN:0020-9309    

DOI:10.1002/iroh.19860710605

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractThe development of a heavy phytoplankton bloom (chl.a= 360 mg/m3), which occurred in the summer 1983 in a shallow reservoir, Divor, is described. The study shows that remobilization of phosphate from the sediment was initiating the phytoplankton bloom. This was confirmed not only by calculations of the change in iron‐phosphate pool, but also supported by sorption experiments carried out with the sediment. It is discussed that turbidity of the water due to suspended matter caused the reduction in standing stock of phytoplankton to approx. 50 mg chl.a/m3in late summe

ISSN:0020-9309    

DOI:10.1002/iroh.19860710606

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractThe process of community metabolism including primary production and community respiration in eighteen undrainable rural fish ponds in India was quantified using the diurnal oxygen curve method. A considerable portion of the gross primary production that was in the moderate ranges, was consumed for the community respiration. Negative, and low positive values of net primary production indicated the significance of the allochthonous supply in these organic enriched systems. The low values of sediment respiration signified the reduced condition of stagnating sediment acting as energy trap.

ISSN:0020-9309    

DOI:10.1002/iroh.19860710607

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Bacillariophyta dominated over the other phyla and were mainly recorded in high densities during summer and autumn. The Chlorophyta and Myxophyta (Cyanobacteria) were represented by coccoid forms and by non‐heterocystous, filamentous forms, respectively. Both were mainly recorded during summer and mostly absent during winter. Other phyla were occasionally recorded in low densities; the Chrysophyta being found in the River Elan and at one site on the River Wye during June 1980. Their members were considered as “contaminants” or “fall‐out” from other communities. Pennate diatoms were the most “constant” species and either showed a general upstream or downstream increase or a general distribution throughout the study area. Populations of the same species colonising both sediments and stones were not correlated or insignificantly correlated with each other at most stations. It was concluded that sediments were unsuitable for algal colonisation. The River Elan and upper Wye were rated as oligosaprobic, the River Ithon and lower Wye as β‐mesosaprobic and the River Lugg

ISSN:0020-9309    

DOI:10.1002/iroh.19860710608

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19860710609

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractWe studied the toxicity of copper onMicrocystis aeruginosaandAphanizomenon flos‐aquae.The toxicity phenomena can be described by the survival dose relationship which allows us to define the three parameters: threshold concentration (Cs), sensitivity (k) and a NL. 50%. The latter corresponds to the copper concentration which reduces the number of cells at the end of the exponential phase by 50%.A. flos‐aquaeis very clearly less tolerant thanM. aeruginosato copper. Viable cell counts based on electron transport activity showed thatM. aeruginosacultures can detoxify cop

ISSN:0020-9309    

DOI:10.1002/iroh.19860710612

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19860710613

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY