Variability of Nutrient Concentrations in Sediments and Wetland Plants during the Vegetation Season under Different Sediment Moisture Conditions

Changes of nutrient concentrations in sediments and plant biomass as well as above-ground biomass production of four emergent macrophytes during the vegetation season were studied. Particularly, variations over time in N:P and N:K ratios in sediments between sites with and without vegetation as well as seasonally flooded and permanently flooded sites were investigated. In plant covered sites, biomass production and nutrient concentrations in the four wetland plant species were measured monthly from March to September 2008. The study was conducted in the littoral zone of the polymictic Lake Niepruszewskie. The performed analyses of N, P and K concentrations in plants and sediments indicated that measurements of nutrients in plant biomass better reflected nutrient availability for plant growth than analyses of nutrient contents in sediments. The vegetation biomass and nutrient concentrations in plant biomass in the shallow littoral zone were more sensitive to changes of water depth in comparison with the permanently flooded part of the littoral zone. The present study showed that the N:P biomass ratio was a better indicator of moisture changes than the N:K ratio or individual nutrients. Preferences of the studied macrophytes for nutrient concentrations in sediments depended more on the N:P ratio in the sediment than N or P or K concentrations individually. Glyceria maxima preferred sites with high N and K concentrations (N:K = 0.9) while Typha angustifolia occurred in sites with the lowest nutrient concentrations among the studied species (N:P and N:K = 0.1).