Natural and constructed littoral zones as nutrient traps in eutrophicated shallow lakes |
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Authors: | Susan Sollie Hugo Coops Jos T A Verhoeven |
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Institution: | (1) Landscape Ecology, Institute of Environmental Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands;(2) RIZA, P.O. Box 17, 8200 AA Lelystad, The Netherlands |
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Abstract: | It is generally known that the water quality of shallow lakes can be influenced significantly by marginal wetlands. In order
to study the efficacy of constructed littoral wetlands in the IJsselmeer area (The Netherlands) for water quality improvement,
a field survey was carried out in 2003. Vegetation, soil, pore water and surface water characteristics were measured in spring
and summer in two types of littoral zones: natural and constructed for 8–16 years. The study showed that constructed wetlands
perform well and are suitable to enlarge the vegetated littoral zone in the IJsselmeer area. In both natural and constructed
sites vegetation biomass varied between 2,200 g m−2 for helophyte vegetation and 1,300 g m−2 for low herbaceous vegetation. Nutrient concentrations in the pore water of constructed sites tended to be higher than in
natural sites.
and concentrations in pore water were much lower when vegetation was present, probably as a result of plant uptake. The N and
P accumulation rate in the soil of constructed wetlands was 20 g N m−2 y−1 and 3 g P m−2 y−1 in vegetated plots; without vegetation the rate was much lower (8 g N m−2 y−1 and 1.8 g P m−2 y−1). We conclude that concerning their effect on water quality, constructed sites may replace natural sites, at least after
8–16 years. Principal component analysis showed a relationship between vegetation biomass and flooding, and nutrient concentrations
in soil and pore water. Biomass was negatively correlated with extractable nutrients and positively with soil total N and
P content. Flooding duration was negatively related to pore water salinity and positively to pore water nutrients. Due to
their high biomass, helophyte stands retained significantly more nutrients than low pioneer vegetation and are therefore more
suitable for improving water quality.
Handling editor: S. Declerck |
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Keywords: | Water quality Phragmites australis Artificial wetland Shallow lake Water level fluctuations Biogeochemistry |
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