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  • 1
    Electronic Resource
    Electronic Resource
    Midsummer spatial variation in methane efflux from stands of littoral vegetation in a boreal meso-eutrophic lake (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Spatial variation of methane (CH4) efflux from the littoral zone of a meso-eutrophic boreal lake was studied with a closed-chamber technique for three summer days in 22 vegetation stands, consisting of three emergent and three floating-leaved species.2. Between-species differences in CH4 emission were significant. The highest emissions were measured from the emergent Phragmites australis stands (0.5–1.7 mmol m−2 h−1), followed by Schoenoplectus lacustris 〉 Equisetum fluviatile 〉 Nuphar lutea 〉 Sparganium gramineum 〉 Potamogeton natans. Within-species differences between stands were not significant.3. In P. australis stands, the stand-specific mean CH4 emission was significantly correlated with solar radiation, probably indicating the role of effective pressurised ventilation on CH4 fluxes. The proportion of net primary production emitted as CH4 was significantly higher in P. australis stands (7.4%) than in stands of S. lacustris and E. fluviatile (both 0.5%).4. In N. lutea stands, CH4 efflux was negatively correlated with the mean fetch and positively with the percentage cover of leaves on the water surface. There were no differences in CH4 efflux between intact N. lutea leaves and those grazed by coleopteran Galerucella nymphaeae. In S. graminaeum and P. natans stands, CH4 effluxes were not related to any of the measured environmental variables.5. For all vegetation stands, the biomass above water level explained about 60% of the observed spatial variation in CH4 emission, indicating the important role of plants as gas conduits and producers of substrates for methanogens in the anoxic sediment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01113.x
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  • 2
    Electronic Resource
    Electronic Resource
    Methane efflux in relation to plant biomass and sediment characteristics in stands of three common emergent macrophytes in boreal mesoeutrophic lakes (2005)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Methane efflux was studied in stands of three emergent macrophyte species (Equisetum fluviatile, Schoenoplectus lacustris and Phragmites australis) commonly found in the littoral zone of boreal lakes. In vegetation stands with relatively low methane (CH4) emissions (〈0.3 mol m−2 (ice-free period)−1), the seasonal variation of CH4 efflux was better correlated with the dynamics of plant growth than variation in sediment temperature. In dense and productive vegetation stands that released high amounts of CH4 (2.3–7.7 mol m−2 (ice-free period)−1), the seasonal variation in CH4 efflux was correlated with sediment temperature, indicating that methanogens were more limited by temperature than substrate supply. The bottom type at the growth site of the emergent plants significantly influenced the ratio of CH4 efflux to aboveground biomass of plants (Eff : B). The lowest Eff : B ratio was found in E. fluviatile stands growing on sand bottom under experimental conditions and the highest in P. australis-dominated littoral areas accumulating detritus from external sources. The future changes expected in the hydrology of boreal lakes and rivers because of climatic warming may impact the growth conditions of aquatic macrophytes as well as decomposition and accumulation of detritus and, thus, CH4 effluxes from boreal lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2004.00888.x
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  • 3
    Electronic Resource
    Electronic Resource
    Response of littoral vegetation on climate warming in the boreal zone; an experimental simulation (2000)
    Springer
    Aquatic ecology 34 (2000), S. 433-444 
    Details
    ISSN: 1573-5125
    Keywords: aquatic macrophytes ; boreal zone ; climate warming ; ecosystem experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of climate warming on the littoral zone of a boreal lake ecosystem was studied experimentally for three growing seasons in two artificial ponds (10×27 m) and in replicated chamber experiments. One pond was enclosed in a plastic greenhouse and another untreated pond served as a reference system. During the growing seasons temperature in the greenhouse was maintained at levels 2–3 °C higher than ambient with a computer-controlled ventilation system. One growing season prior to initiation of the experiment, a vegetated littoral zone with equal densities of water horsetail (Equisetum fluviatile) was established in both ponds. Although changes occurred in the species dominance (E. fluviatile - Alisma plantago-aquatica - Sparganium erectum spp. microcarpum - Elodea canadensis) within the three years of the study, the emergent macrophytes emerged earlier and grew better in the warmer conditions of the greenhouse pond compared with those in the reference pond. The difference in above-ground biomass throughout the growing seasons was 〉2 fold and after three experimental growing seasons the difference in below-ground biomass of macrophytes was 2.5-fold between the ponds. In replicated chamber experiments the biomass growth of E. fluviatile was also significantly higher in a 2–3 °C higher temperature than under ambient conditions. An ecosystem-scale induced change, characterized by a heavy growth of filamentous algae (mainly chlorophytes) was evident in the vegetated littoral zone of the greenhouse pond. A hypothesis that macrophyte rhizomes function as `phosphorus pumps' from the sediment and thus accelerate eutrophication in a warmer climate should be further studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011457815299
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  • 4
    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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