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  • carbon dioxide  (1)
  • clearance rate  (1)
  • 1
    ISSN: 1573-5117
    Keywords: eutrophication ; Microcystis ; reservoir restoration ; phosphorus precipitation ; carbon dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Bautzen reservoir, a shallow, hypertrophic water in Eastern Saxony, biomanipulation led to structural changes in the phytoplankton community but did not reduce algal biomass. To supplement the top-down management, a new type of water treatment technology was tested during two seasons (May–August 1996/1997), aiming at the bottom-up control of mass developments of the cyanobacterium Microcystis aeruginosa.The technology is based on a combined lake–internal phosphorus precipitation and a transport of hypolimnetic water rich in free carbon dioxide into the upper layers. During the treatment periods, there were found both an increase of CO2concentrations in the mixed layer and an extension of the period in which free CO2was detected in the epilimnion. The concentrations of phosphorus could be lowered drastically in the whole water body. Microcystiswas almost totally suppressed (1996) or appeared with a delay (1997) compared to the regular annual pattern observed before the treatment. In contrast to the preceding year (1995), diatoms played a major role in the summer phytoplankton during the treatment years (1996/1997). The two application periods are compared with respect to the influence of meteorologically determined variables.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: bacteria ; phytoplankton ; daphnids ; clearance rate ; ingestion ; biomanipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We determined clearance rates and ingestion rates of Daphnia galeata on bacteria and phytoplankton in order to test if bacteria are an important alternative food resource for daphnids during periods of low phytoplankton biomass in the biomanipulated Bautzen reservoir (Germany). D. galeata was able to feed on bacteria with the same efficiency as on algae during most of the time. In spite of similar clearance rates, bacteria ingestion was usually lower than phytoplankton ingestion due to lower bacterial biomass. Only at low biomass of algae in late fall and during the clear water phase, bacteria contributed up to 87% and 42%, respectively, to total carbon ingestion of D. galeata. However, even a short period of relatively high bacteria grazing by daphnids may be important for biomanipulation. Bacteria might bridge over periods of food limitation of daphnids thus promoting the maintenance of high Daphnia biomass. Therefore, ingestion of bacteria by daphnids is thought to stabilize biomanipulation and may hold a key position in the food web of biomanipulated lakes.
    Type of Medium: Electronic Resource
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