Nitrogen and phosphorus concentration of different structures of the aquatic macrophytes Eichhornia azurea Kunth and Scirpus cubensis Poepp & Kunth in relation to water level variation in Lagoa Infernão (São Paulo, Brazil)

Abstract

We evaluated the nitrogen and phosphorus concentration of floating meadows of Eichhornia azurea and Scirpus cubensis in Lagoa do Inferno (State of Sao Paulo, Brazil) . The chemical composition of these plants and of the water (littoral and limnetic zones) was determined during the period March 1987 to march 1988 . During high water, the water becomes enriched by soluble nutrients and particulates washed from the flooded areas adjacent to the lake, especially from areas situated between the river and Lagoa do Inferno . The soluble allochthonous material is rapidly assimilated and stocked in the plant tissues, which results in an increase in its concentration . Besides this, it was established that the aquatic macrophytes studied utilize the nutrients dissolved in the water of the floating meadow itself, these nutrients being derived principally from their own decomposition .Since these are floating stands, the sediment does not function as a direct source of nutrients, and since concentrations in the water are low, the nutrients excreted by the aquatic macrophytes during growth and liberated during decomposition do not remain available in the water, but are rapidly absorbed by the young plants . This closed nutrient system makes possible the maintenance of the high biomass of the stands during the entire hydrological cycle .

Flood pulse influence and anthropic impact on the chemical composition and energy content of Oryza glumaepatula in an Amazonian lake

“…This characteristic is even more pronounced in ecosystems with low nutrient concentrations, such as the clear and black water Amazonian ecosystems (Sioli, 1984;Setaro & Melack, 1984;Esteves et al, 1990). The participation of aquatic macrophytes in nutrient cycling has been verified by many authors (e.g., Granéli & Solander, 1988;Nogueira et al, 1996), who have demonstrated the role of this community in the absorption of nutrients from the sediment as well as their liberation in the water column.…”

The value of the Ecological Station of Jataí's ecosystem services and natural capital

“…However, this oxbow lake stands out of the Ecological Station of Jataí limits, in a degraded landscape resulting from different types of land use, such as intense deforestation, pasture and agricultural activities. However, nitrogen and phosphorus dynamic cycles in Infernão Lake, inside the Ecological Station of Jataí, evidenced an increase of nutrient concentration during rainy season (Nogueira et al, 1996). It seems that oxbow lake works as a sink compartment, since nutrients were quickly assimilated by the producers.…”

“…In general, aquatic and flooded areas on Ecological Station of Jataí are better able to decompose large amounts of organic matter with respect to flood pulse, and without evidences of eutrophication process. Some idea of intense metabolic activity that accompanies organic matter degraded is obtained by observation of the increase temperature in the substrate and water column of oxbow lakes (Ballester, 1994;Camargo & Esteves, 1995;Nogueira et al, 1996;Albuquerque & Mozeto, 1997), and also the high populations of micro-organisms (Freitas, 1989).…”

“…When nutrient rich water enter on flooded area, nitrogen and phosphate are effectively trapped and assimilated in the productive biological systems (e.g. aquatic macrophytes and phytoplankton of oxbow lakes and riparian vegetated strips) (Nogueira et al, 1996;Albuquerque & Mozeto, 1997).…”

“…Certain natural fragments and riparian forests can be considered as corridors wich enable animals to move from one habitat to the next. Mogi-Guaçu River wetland with a expressive net biomass production (Nogueira et al, 1996;Coutinho, 1989) is especially important as feeding and resting habitats (Talamoni, 1996). In general, it can be considered that higher the net-production biomass, the more migratory species can be supported by a given ecosystem (De Groot, 1992).…”