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  • 1
    Electronic Resource
    Electronic Resource
    On the importance of dissolved organic matter in the nutrition of zooplankton in some lake waters (1986)
    Springer
    Oecologia 68 (1986), S. 246-253 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A steady state, radiotracer technique was used to study the original source of the carbon in zooplankton. The experiments were started in filtered lake water with added inorganic radiocarbon. At the beginning of the experiments, a proportionally insignificant volume of unfiltered water was introduced into the culture, together with some ovigerous zooplankton individuals. Since the radioactivity: carbon ratio in the dissolved inorganic carbon was kept constant, a similar ratio would be expected to develop in the autotrophic phytoplankton. The same ratio would then be expected to develop in the zooplankton, if its sole carbon source was autotrophic phytoplankton. According to the results of this approach dissolved organic matter seems to be an important food resource for zooplankton, particularly in highly humic lakes. This conclusion was confirmed by the finding that zooplankton from these lakes was able to grow and reproduce in experiments started with filtered lake water and conducted in complete darkness. The development of algae was followed over the course of one experiment in highly humic water. The same micro-flagellates reproduced equally well in both light and darkness, which indicates the importance of heterotrophic metabolism in their nutrition. Although there are no direct observations about the food of zooplankton in our experiments, it appears likely that heterotrophic flagellates play an important role as a food of zooplankton in humic waters. The importance of dissolved organic matter in the nutrition of aquatic organisms would seem to be much greater than has generally been recognized. Consequently the prevailing concepts of the structure and functioning of planktonic ecosystem should be thoroughly re-evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384795
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of different preservation methods on the carbon content of megacyclops gigas (1980)
    Springer
    Hydrobiologia 72 (1980), S. 281-285 
    Details
    ISSN: 1573-5117
    Keywords: Preservation ; fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of various preservation methods on the carbon content of the copepod Megacyclops gigas was studied using the carbon content of living animals as a control. No differences were found between animals dried at −20, +60, or +105°C, but in all cases the carbon content was slightly lower than that found in living animals. Chemical preservation with formaldehyde and acid Lugol's solution rapidly resulted in about 35% loss of carbon. Freezing at −20°C in water caused less marked but significant loss of carbon, whereas freezing in dilute formaldehyde yielded values agreeing with those of living animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00005632
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of different glass fibre and silver metal filters for the determination of particulate organic carbon (1979)
    Springer
    Hydrobiologia 67 (1979), S. 29-32 
    Details
    ISSN: 1573-5117
    Keywords: Filtration ; determination of particulate organic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The most retentive glass fibre filters were able to retain almost all bacteria from the water of an oligotrophic lake. Having satisfactory speed and capacity, of filtration this type of filter is quite near to the ideal which should be able to include all algae and bacteria in the category of particulate organic carbon. Similar retention could also be achieved by silver filters but, because of their high blank values, price, and lower filtration speed and capacity, they are not able to compete with glass fibre filters in practical work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020875
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  • 4
    Electronic Resource
    Electronic Resource
    A multiple filtration device for glass fibre filters (1979)
    Springer
    Hydrobiologia 67 (1979), S. 27-28 
    Details
    ISSN: 1573-5117
    Keywords: Filtration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A practical multiple filter holder is described for collection of particles on glass fibre filters. The device utilizes large diameter discs and the ends of individual filter tubes compress against the filter so that, after filtration, the separate filtering areas can easily be taken from the large disc with forceps. If analyses of collected particulate matter are to be made at a later time, the filtering areas are left attached to the original filter. Precise volumes of water can be filtered by attaching volumetric pipettes to individual filter tubes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020874
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  • 5
    Electronic Resource
    Electronic Resource
    Photochemical mineralization of synthetic lignin in lake water indicates enhanced turnover of aromatic organic matter under solar radiation (1999)
    Springer
    Biodegradation 10 (1999), S. 415-420 
    Details
    ISSN: 1572-9729
    Keywords: Carbon cycling ; humic matter ; lignin ; mineralization ; photocatalysis ; solar radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The degradation of 14C-[ring]-labelled syntheticlignin (14C-DHP) and dissolved organic carbon(DOC) from lake water were studied simultaneously.14C-DHP was incubated in humic lake water (colour173 mg Pt l-1) for 7 d in the dark or under solarradiation. In the dark 〈0.4% of the introduced14C-DHP label and 4% of the indigenous DOC weremineralized, indicating that the 14C-labelledaromatic rings of DHP and the humic DOC weremicrobiologically recalcitrant. Under solar radiation(116 MJ m-2), 17–21% of the 14C-labelledcarbons in DHP and 18–23% of the indigenous DOC weremineralized in 7 d. Simultaneously the watersolubility of 14C-DHP increased. Solar radiationconverted the aromatic cores of synthetic lignin toCO2 and soluble organic photoproducts. Theresults suggest that solar radiation plays a key rolein the decomposition of natural polyaromatic matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008322520299
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  • 6
    Electronic Resource
    Electronic Resource
    Migrations of haemoglobin-rich Daphnia longispina in a small, steeply stratified, humic lake with an anoxic hypolimnion (1992)
    Springer
    Hydrobiologia 229 (1992), S. 271-288 
    Details
    ISSN: 1573-5117
    Keywords: Daphnia longispina ; haemoglobin ; vertical migration ; humic lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Migrations of Daphnia longispina were studied in a small humic lake with an exceptionally shallow oxic epilimnion. Horizontal distributions showed clear avoidance of the shoreline, which might be explained by the lower density of predators (Chaoborus sp. and Notonecta sp.) in the central parts of the lake. In early summer all size classes of D. longispina exhibited upward nocturnal vertical migration, descending to the upper hypolimnion in daytime. Later in summer, when the nocturnally migrating Chaoborus sp. had grown large enough to graze on small Daphnia, the latter seemed to shift towards twilight migration. However, large Daphnia individuals showed no synchronized migration; rather their bimodal vertical distributions suggested asynchronous vertical migration. Large individuals showed a particular tendency to concentrate near to the oxycline, close to the dense phytoplankton and bacteria populations in the upper part of the anoxic hypolimnion. According to vertical trap experiments, large D. longispina visited the anoxic hypolimnion and might harvest its abundant food resources. The high haemoglobin content of large individuals seems a specific adaptation to allow access to low oxygen water and hence to maximize grazing potential, in both epi- and hypolimnion, and minimize predation pressure. By staying predominantly in cooler water near the oxycline, Daphnia might also minimize its energy consumption to adjust to low food availability while sustaining a sufficiently high population density to exploit those unpredictable short periods with abundant food which are common in small headwater lakes. It is suggested that migrations of zooplankton are a complex behavioural adaptation which may not be explained by any single factor. In humic lakes with shallow stratification, vertical migrations seem to offer particularly high potential advantages, because of the short distances between dramatically different environments in the water column. In further studies more emphasis should be placed on migrations of individuals rather than populations, and migrations should be considered as a dynamic part of the structure and function of the whole planktonic ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007005
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  • 7
    Electronic Resource
    Electronic Resource
    Bacterioplankton in a small polyhumic lake with an anoxic hypolimnion (1992)
    Springer
    Hydrobiologia 229 (1992), S. 159-168 
    Details
    ISSN: 1573-5117
    Keywords: bacterioplankton ; polyhumic lake ; photosynthetic bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterioplankton biomass and dark fixation of inorganic carbon were measured in the highly humic (water colour up to 550 mg Pt l−1) and acidic lake, Mekkojärvi. Strong thermal and chemical stratification developed in the water column early in spring and led rapidly to anoxia in the hypolimnion, which extended to less than 1.0 m from the surface. In the epilimnion only small bacteria were abundant. In the anoxic zone both the abundance and the mean size of bacteria were considerably higher than in the epilimnion. These differences are thought to be the result of different grazing pressure from zooplankton in the two zones. In late summer a high concentration of bacteriochlorophyll d in the upper hypolimnion indicated a high density of photosynthetic bacteria. Bacterial biomass was similar to that of phytoplankton in the epilimnion, but 23 times higher in the whole water column. In August, dark fixation of inorganic radiocarbon in the anaerobic zone was 51% of the total 14C-incorporation and the contribution of light fixation was only 5.4%. In the polyhumic Mekkojarvi, bacterioplankton was evidently a potentially significant carbon source for higher trophic levels, but bacterioplankton production could not be supported by phytoplankton alone. Allochthonous inputs of dissolved organic matter probably support most of the bacterial production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006998
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  • 8
    Electronic Resource
    Electronic Resource
    Variation in the carbon content of two Asplanchna species (1988)
    Springer
    Hydrobiologia 162 (1988), S. 79-87 
    Details
    ISSN: 1573-5117
    Keywords: Asplanchna ; biomass ; carbon content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rotifers of the genus Asplanchna were sampled four times during the summer from eight lakes of different types. The mean individual carbon content in the population varied between 0.15–0.66 µg C ind.-1 (n = 21) for A. priodonta and 1.0–1.6 µg C ind.-1 (n = 3) for A. herricki. The carbon content and the size of A. priodonta varied considerably between the populations of both different lakes and dates. The carbon level of both Asplanchna species (sample mean 0.2–1% of wet weight) was considerably lower than is generally found for rotifers. Much of the variation of carbon level could be explained by an inverse relationship with wet weight. The high variation in the carbon content of individuals suggests that Asplanch population may adapt their mean body size to fit prevailing environmental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014335
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  • 9
    Electronic Resource
    Electronic Resource
    Flagellate grazing on bacteria in a small dystrophic lake (1988)
    Springer
    Hydrobiologia 161 (1988), S. 203-209 
    Details
    ISSN: 1573-5117
    Keywords: Bacteria ; flagellates ; grazing ; humic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fluorescent beads were used to determine the grazing on bacteria by heterotrophic and mixotrophic flagellates in a highly humic (water colour 300–600 mg Pt l−1) small lake. In summer phagotrophic flagellates constituted about three quarters of the numbers of phytoplankton (including heterotrophic or mixotrophic flagellates) in the uppermost epilimnion. Due to their small size their respective contribution to the biomass was about one quarter. The most important phagotrophic species were Ochromonas sp., and Chromulina spp. which ingested 75–203% of their body carbon per day from bacteria. In view of the abundance and biomass of phagotrophic and mixotrophic flagellates and their very high growth potential, they clearly play a significant role in the food chains of this lake. In addition to providing energy, bacteriovory also represents an important supply of inorganic and organic nutrients under nutrient limiting conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044111
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  • 10
    Electronic Resource
    Electronic Resource
    Growth of Daphnia longispina L. in a polyhumic lake under various availabilities of algal, bacterial and detrital food (1995)
    Springer
    Hydrobiologia 315 (1995), S. 119-134 
    Details
    ISSN: 1573-5117
    Keywords: Daphnia longispina ; humic lakes ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The availability and importance of food sources for growth of Daphnia longispina L. from a highly coloured fishless lake with anoxic hypolimnion were assessed by combining in situ and laboratory experiments. In in situ experiments populations were enclosed in tubes with natural temperature stratification and with or without anoxic hypolimnion. In the laboratory experiments the importance of food source (littoral zone vs pelagic epilimnion) was assessed by enclosing moss thalli and a natural zooplankton population in a large-scale flow-through system supplying food for experimental Daphnia. Growth of juveniles of Daphnia in epilimnetic water was determined in batch culture experiments and the importance of increasing concentrations of bacteria and algae for their growth and development was investigated with a small-scale flow-through system. Access to the anoxic hypolimnion enhanced the growth of Daphnia by 23–24%. Growth rates in the tubes with anoxic hypolimnion were 0.36 and 0.16 d−1 in July and August respectively. In tubes without anoxia the corresponding values were 0.29 and 0.13. In batch-cultures the highest growth rate determined was 0.16 and the overall rates were lower than in in situ experiments. In batch culture Daphnia was able to grow in darkness for 10 days with a rate of 0.16. In the large-scale flow-through system Daphnia population fed with littoral water reproduced well despite the low concentration of algae and increased its number by a factor of c. 32 in 10 days. However, the animals were small and net production of Daphnia population thus lower under the littoral influence than in the control treatment. Population could survive and grew slowly on pelagial water processed by a natural zooplankton community and with very little algae left. It is thus possible that bacteria serve as a ‘life-support system’ enabling the population survival over periods of algal shortage. Small-scale flow-through experiments revealed that Daphnia longispina is able to mature and reproduce on a bacterial diet if the food concentration is high enough and Daphnia on bacterial food could achieve growth rates similar to those on an algal diet. The threshold food level for Daphnia longispina was estimated to be c. 18.5 μg C 1−1. Detrital material is of limited value in nutrition of Daphnia even in a lake where more than 75% of carbon is bound in particulate detritus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033624
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