摘要:

SUMMARY.Five populations ofAsellus aquaticus, subjected to different combinations of temperature and organic pollution in the River Trent, were examined over a period of 18 months. The life‐cycle was probably completed in a year or less in all the populations sampled, a larger proportion of the animals completing the life‐cycle in less than a year at warmer locations. Young animals also hatched 1 or 2 months earlier at the warmer locations.At the locations subjected to most organic pollution, population densities and the size of animals of both sexes were the largest. The size of ovigerous females, however, appeared to be inversely related to temperature, the smallest occurring at the warmest location. Possible explanations for these differences are given in terms of the amount of food available and the effect of temperature on growth and sexual maturat

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01175.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.The ciliate communities occurring at three benthic sites in a small eutrophic loch have heen investigated over a 2‐year period. Two characteristics of the community were studied in detail, the pattern of vertical distribution within the sediment and the temporal distribution of ciliates occurring in the surface sediment. The relationships between ciliate distributions and the environmental factors recorded were analysed by multiple regression. Significant relationships were revealed between vertical distribution of ciliates and the sediment redox (Eh) profile, the larger ciliate communities being associated with regions of higher potential. Other factors such as sediment density, organic matter, temperature and daylength, combined with other indicators of benthic metabolism (sulphide ion activity (Es2−), pH, oxygen flux) were selected in the regression analysis as accounting for much of the variation in the depth distribution of ciliates.In analysing the temporal distribution of ciliates in the surface sediment, numbers were inversely related to Eh, Es2−and oxygen flux, a result of the upwards migration of reducing conditions and greater microbial activity in the sediment surface during the summer. Daylength, temperature, organic carbon and benthic chlorophyll‐awere also selected as accounting for much of the variation in ciliate number. It is proposed that the large increases in number and biomass of surface‐sediment cilates in the summer months resulted from an intolerance of reducing conditions developing immediately beneath the surface and the increased productivity of the benthos as a whole during this period.Methods are also described for the construction, calibration and operation of electrodes used in measuring Eh, Es2−and oxygen flux in the freshwater benthos. Data recorded for these three variables revealed similar seasonal patterns at each site in each of two consec

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01176.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.The diel patterns of reproduction were studied for three rotifer populations from Lake Valencia, Venezuela. Significant departures from uniformity were recorded for egg eclosion and egg deposition rates inKeratella americanaandBrachianus calyciflorus, but only from egg deposition rates inB. havanaensis. The existence of non‐random reproduction has practical ramifications for studies of population dynamics and secondary productio

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01177.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.On the basis of material from over seventy acidic water bodies in three different areas a relationship is revealed between pH and the species diversity of their crustacean faunas. With increasing acidity species diversity decreases. No such relationship is shown between calcium concentration and species diversity. The very low calcium levels of such waters may, however, play a part in the exclusion of certain species.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01178.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.The lakes of Signy Island (60° 43′S, 45° 38′W), South Orkney Islands, Antarctica, provide a unique laboratory for the study of many processes including natural eutrophication. Current relationships between the lakes have been examined by principal components analysis of environmental data from a long‐term monitoring programme. The results from the analysis have been combined with some biological data to provide a classification scheme for the lakes. The study has produced a valuable baseline for use in future r

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01179.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.Scales of several members of the Chrysophyceae (family Synuraceae) were examined from a core of the recent sediments of Hall Lake, Washington, in conjunction with a study of fossil diatoms. Both types of microfossils revealed communities changing with the historical development of the lake. Increases in planktonic diatoms and in two species ofMallomonasoccurred about the time of European settlement. Several acidophilous species among the Chrysophyta disappeared with the establishment of a sawmill and meromictic conditions in the lake. When extensive road construction around the lake ended the period of meromixis, the ratio of Synuraceae, in general, to diatoms, declined. Besides the change in ratio of Synuraceae to diatoms there was a change in the composition of the community of Synuraceae at that time. Species ofSynurathat had been rare before became the most abundant, andMallomonasbecame relatively rare. Throughout the recent history of the lake the dominant Synuraceae seemed to respond more strongly to disturbance around the lake than the most abundant diatoms; thus, scales ofMallomonas, Synura, and other Synuraceae are valuable microfossils for paleolimnological studies.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01180.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.The bdelloid rotifers and nematodes of a small clean watercourse in the area surrounding the Po river near Parma have been studied. The samples were collected at two sites 400 m apart. The species found in twelve collections of benthos between May 1977 and June 1978 were eighteen belonging to Bdelloidea and forty‐seven to Nematoda (Tylenchida have not been considered). Nearly all the bdelloid species were oligosaprobic or beta‐mesosaprobic; the Shannon index of diversity was 3.0 at the first site and 2.4 at the second. Among the Nematoda the dominant species wereParaplectonema pedunculatum and Paraphanolaimus anisitsiwhich were not previously recorded for Italy. Nearly all nematodes are microphagous; predators represent only 10% of collected specimens. Polluted water indicator species (Secernentia group) were only 3.5% of the total nematodes recorded. Most rotifers and nematodes did not show seasonal fluctuations in numbers. The two sampling sites do not seem to have substantial differences in the taxocoenosis of Rotifera and Nematoda; their percentage of similarity is 69% and 79% for the two classes respectiv

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01181.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.Lake Dakataua (5°S, 150°E) is a large freshwater lake which fills the caldera at the tip of the Willaumez Peninsula on West New Britain, Papua New Guinea. A peninsula produced by post‐collapse volcanic activity divides the lake into two basins connected by a narrow channel. The surface of the lake isc. 76 m above sea level, the surface area is 48 km2, and the maximum depthc. 120 m (Lowder&Carmichael, 1970). A bathymetric map of the lake has been constructed from fathometer transects.In October‐November, 1974, the lake was alkaline throughout with surface pH 7.6–8.2; acidity increased with depth to pH 7.1–7.5. Surface temperatures were 30.8–31.9°C. There were thermoclines at 22 m and at 40–45 m. Minimum temperature recorded was 26.8°C (at 80 m). Oxygen saturation curves were similar to the temperature curves with sharp gradients at 22 m and 40–45 m. There was no measurable O2from 80 m downward. Living organisms were common in dredge hauls to 20 m but were not found in those from greater depths. Carbon dioxide concentration rose steadily from 1.4 mg I−1at the surface to 19.6 mg I−1at 80 m. Average Secchi disc transparency was 11.1 m.Shallow water areas support dense beds of mixed aquatic plants (Najas tenuifolia and Charasp.). Invertebrates collected included two species of sponge, a rotifer, an ostracod, six species of molluscs, seven species of Cladocera, a copepod, eight species of Hemiptera, two species of Trichoptera, ten species of Odonata, two species of Coleoptera, and seven species of Chironomidae. Vertebrates included frogs (two species) and crocodiles. Water birds, including ducks, grebes, and waders, were abundant. The biota of L. Dakataua is more diverse than that of nearby Lake Wisdom probably due to the combination of greater age and greater proximity to sources of colonists. Most species found in L. Wisdom are also

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01182.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARY.The crustacean Zooplankton community in Bough Beech, a flooded valley reservoir in south‐east England, was investigated in the early years of impoundment. The nutrient status and phytoplankton were typical of a lowland eutrophic lake, and this was reflected in the composition of the Zooplankton. At any given time, the latter comprised one or two cladoceran and two or three copepod species, of which the cladocerans were generally numerically predominant. Marked alterations in the Zooplankton community occurred in the first 2 years of the study and were related to changes in predation pressure by fishes. By the end of the third year, the composition of the Zooplankton community had stabilized.The cladoceran biomass was normally in excess of that of the copepods, with maxima in spring and autumn. Peaks in copepod biomass occurred within 2 months of those of the Cladocer

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01183.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Kiefer, F.&Fryer, G. (1978).Das Zooplankton der Binnengewässer.Roberts, R.J. (Ed.) (1978).Fish Pathólogy.Gerking, S.D. (Ed.) (1978).Ecology of Freshwater Fish Production.Golterman H.L., Clymo R.S., andOhnstad M.A.M. (1978)Methods for Physical and Chemical Analysis of Fresh Wate

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1980.tb01184.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY