Fluxo de nutrientes em um sistema de aquicultura orgânica

Abstract

The cultivation of marine shrimp in organic system has become an alternative less harmful to the environment. The union of this system with the integrated cultivation (seaweed–shrimp) is an economically and socially beneficial way of reducing environmental impacts from this activity. This study focuses on the nutrient flow in an organic shrimp (Litopenaeus vannamei) farming system and on the ability of macroalga Gracilariopsis tenuifrons, Gracilaria caudata, Ulva lactuca and Gracilaria domingensis to absorb nitrogen and phosphorus when grown in this system. This thesis is composed of four chapters. The chapter 1 is in the form of introduction that highlights the current state of aquaculture, the cultivation systems, the current knowledge of integrated cultivation and the most commonly used algal species as biofilters. This chapter also justifies and emphasizes the need to undertake the current research. The chapter 2 analyzes the nutrient (NH4 + , NO2 - , NO3 - and PO4 - ) flow and assesses the environmental parameters in the organic shrimp (Litopenaeus vannamei) farm. In this study, the water and sediment quality from the shrimp farm were determined for a period corresponding to one cycle of the shrimp. These data were combined with information on the physical and chemical parameters in order to investigate which variables influence the shrimp growth and survival. The chapter 3 evaluates the relationship among nutrient loading and nutrient removal and assimilation rate by macroalgae Gp. tenuifrons when grown in organic farming wastewater. Aspects related to algal physiology, such as pigment composition, photosynthetic rate and growth were evaluated in the laboratory. Finally, in the chapter 4, the bioremediation potential and nitrogen and phosphorus assimilation of G. Caudata, G. domingensis and U. lactuca were estimated in outdoor. Evaluation of the integrated organic farming role is also discussed. All these chapters give shape to this research and they may be seen as important data for organic aquaculture.