Influência do enriquecimento por fósforo sobre o desenvolvimento da macrófita aquática flutuante livre Salvinia sp.

Abstract

Aquatic weeds are plants that live from swamps to truly aquatic environments. It is a diverse group of organisms that grows permanently or periodically submerged or floating on the water surface, representing one of the main producers of organic matter in environments where they occur. The factors that influence its development are: light, temperature, nutrients, pH, alkalinity, salinity, current speed and variation of the watermark level. The overgrowth of weeds in aquatic environments can, in many cases, become undesirable as it undermines the multiple uses of water (irrigation, supply, recreation and power generation). In southern Brazil, is exacerbated growth of free floating fern Salvinia sp. in aquatic environments for the fish or the water supply which, in addition to changing the balance of aquatic communities, can bring harm to the activities involving the use of water from these environments. The present study aimed to evaluate the effects of increasing concentrations of phosphorus in the development of Salvinia and contributing to the knowledge of species’ autoecology. The study was developed in the dam Ecological Trail of UTFPR – Dois Vizinhos. Mesocosms experimental systems have been deployed in the pelagic region of the dam, forming controlled conditions for treatments. The following treatments were established: control treatment, oligotrophic treatment; mesotrophic treatment; and supertrophic treatment, in triplicate. Individuals of Salvinia inoculated remained for a period of 4 weeks during which it was conducted to control and maintain the availability of phosphorus in water in order to maintain the balance of trophic state of each treatment. Considering the weekly average it was found that the concentration of nutrients present in the water of the tanks showed lower values in the control treatments and oligotrófico and higher in mesotrophic and supertrófico. The results obtained by analysis of variance (ANOVA - One Way) showed that the contents of dry matter and nutrient concentration significantly different in lower and higher concentrations treatments, control and supertrophic. In the other, where the trophic limits were close, variations do not show significant. The canonical correspondence analysis (CCA) showed that in treatments where the phosphorus concentration in the water was greater, Salvinia developed quickly and increased their biomass. In this study it was possible to prove that in eutrophic environments where environmental variables are presented in balance, the cultivation of aquatic weeds is favored. These plants when properly handled, can be used to purify eutrophic water environments, taking the nutrients present in the water and incorporating a biomass.