The relationship between the macrophyte vegetation and the nutrient concentration of the water and the sediment of a stream was studied. The small stream is fed by calcareous groundwater. The alteration in the macrophyte vegetation of the stream Rotbach from oligotrophic community towards more eutrophic species is associated with an increasing concentration of nutrients in the sediment. Particularly the concentration of SRP-P in the interstitial water changes significantly.
In terms of the macrophyte vegetation the stream can be divided into 4 floristic zones, A-D. The zones are labelled in a sequence according to their sediment's nutrient content. The chemical analyses of the water and the sediment show the highest concentrations in zone D. It is characterized by the presence of Zannichellia palustris. The zones A-C have almost the same very low nutrient concentration in the water but show a different content of nutrients in the sediment, particularly of the SRP-P in the interstitial water. Zone A which is dominated by Chara hispida shows the lowest SRP-P in the interstitial water. Within zone B which is characterized by Mentha aquatica and Nasturtium officinale and even more in zone C where Chara hispida is less abundant and Elodea canadensis occurs, the SRP-P content is elevated.
The nutrient concentration in the sediment is clearly associated with changes in the macrophyte vegetation of the stream Rotbach. 相似文献
The Changjiang (Yangtze River) is known to contribute significantly to the eutrophication that has caused drastic changes to the ecosystem of the East China Sea. However, evidence for historical changes in nutrient concentrations and composition and the consequent effects on the ecosystem in the coastal water is sparse. In this paper we present some long-term data for nutrient concentrations and Si:N:P ratios in the freshwater and the river plume and the long-term response of the ecosystem structure in the river plume. These data reveal increases in the dissolved inorganic nitrogen and phosphate concentrations in the Changjiang freshwater by a factor of five from the1960s to the end of the 1990s and a reduction in dissolved silicate by two thirds over the same period. Concomitantly, an increase in DIN concentration and a reduction in silicate concentration both by a factor of two were observed in the surface water of the Changjiang plume. As an ecological consequence to such nutrient changes, the chlorophyll a concentration increased by a factor of four since the 1980s and harmful algal blooms increased rapidly since 1985 in the Changjiang estuary and adjacent sea areas. The macrozoobenthic biomass decreased sharply from the mid 1980s to the present, suggesting that the Changjiang estuary has been in a high eutrophication state since that time. We predict that, due to the continuously increasing nutrient pressure, the symptoms of eutrophication associated with nutrients will worsen in the Changjiang plume in the near future. 相似文献