Evaluation of phytoplankton and epipelon responses to different restoration techniques of the eutrophic ecosystems

Abstract

The increase in phytoplankton biomass is one of the main causes of eutrophication, which is a worldwide problem and needs to be reversed. The photosynthetically active epipelon contributes to phosphorus immobilization at the bottom of the ecosystems, but in eutrophic systems that practically nonexistent community. Many techniques are used for the purpose of reversing eutrophication; however, most studies focus on temperate lakes and do not include assessment of epipelon changes. In this sense, we will evaluate experimentally the phytoplankton and epipelon responses to treatments with different restoration techniques for shallow lakes and reservoirs. The main questions to be answered are: i) What treatment has a negative effect on the water P concentration and phytoplankton biomass?; ii) What treatment favors the formation of a photosynthetic active epipelon? making the epipelon photosynthetically active?; iii) What treatment promotes the highest change in the taxonomic structure of phytoplankton?; iv) Can combination of two techniques increase phosphorus immobilization and reduce phytoplankton biomass? Two experiments will be performed in situ in open-bottom mesocosms in the Garças Lake (PEFI, São Paulo). Sampling for determination of physical, chemical and biological variables will be performed at 7th, 14th, 21st, 28th, 60th and 90th day of the experimental period. Seven treatments in triplicates will be performed: C, control (without any technique); Pr, use of periphyton as bioreactor; Mf, introduction of floating macrophytes; Msub, introduction of submerged macrophytes; As, introduction of clay with seeds of submerged macrophytes; Ae, use of aeration with air bubbles in the bottom; Ox, use of aeration with oxygen gas in the bottom. The results generated by the development of this research may support future processes for the restauration of eutrophic lakes and reservoirs. (AU)