The role of solid waste materials as habitats for macroinvertebrates in a lowland dam reservoir |
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Authors: | Magdalena Czarnecka Małgorzata Poznańska Jarosław Kobak Norbert Wolnomiejski |
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Institution: | (1) Plant Science and Nature Management, Department of Biology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium |
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Abstract: | Eight hypereutrophic phytoplankton dominated ponds from the Brussels Capital Region (Belgium) were biomanipulated (emptied
with fish removal) to restore their ecological quality and reduce the risk of cyanobacterial bloom formation. Continuous monitoring
of the ponds before and after the biomanipulation allowed the effects of the management intervention on different compartments
of pond ecosystems (phytoplankton, zooplankton, submerged vegetation and nutrients) to be assessed. Fish removal resulted
in a drastic reduction in phytoplankton biomass and a shift to the clear-water state in seven out of eight biomanipulated
ponds. The reduction in phytoplankton biomass was associated with a marked increase in density and size of large cladocerans
in six ponds and a restoration of submerged macrophytes in five ponds. The phytoplankton biomass in the ponds with extensive
stands of submerged macrophytes was less affected by planktivorous fish recolonisation of some of the ponds later in the summer.
The two non-vegetated ponds as well as one pond with sparse submerged vegetation showed a marked increase in phytoplankton
biomass associated with the appearance of fish. Phytoplankton biomass increase coincided with the decrease in large Cladocera
density and size. One pond lacking submerged macrophytes could maintain very low phytoplankton biomass owing to large Cladocera
grazing alone. The results of this study confirmed the importance of large zooplankton grazing and revegetation with submerged
macrophytes for the maintenance of the clear-water state and restoration success in hypereutrophic ponds. They also showed
that large Cladocera size is more important than their number for efficient phytoplankton control and when cladocerans are
large enough, they can considerably restrain phytoplankton growth, including bloom-forming cyanobacteria, even when submerged
vegetation is not restored. The positive result of fish removal in seven out of eight biomanipulated ponds clearly indicated
that such management intervention can be used, at least, for the short-term restoration of ecological water quality and prevention
of noxious cyanobacterial bloom formation. The negative result of biomanipulation in one pond seems to be related to the pollution
by sewage water.
Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle
Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16
May 2008 |
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Keywords: | Biomanipulation Ponds Fish removal Submerged macrophytes Phytoplankton Large Cladocera size |
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