Balances of carbon, nitrogen and phosphorus in multi-spacial and multi-trophic systems with nile tilapia and amazon river prawn.

Abstract

The use of substrates in aquaculture systems provides additional spaces for periphyton settlement, which accumulates carbon, nitrogen and phosphorus. Thus, increasing periphyton community increases the availability of minerals for reared species. The analysis of balance is an important tool to best understand the nutrients cycle in the system by measuring the output of these nutrients and subtracting from the inputs and, and to assess and quantify these elements, was designed an experiment with twelve natural pounds stocked with 22 juveniles/m2 of freshwater prawn (Macrobrachium amazonicum) and 1.1 juveniles/m2 of tilapia (Oreochromis niloticus). These species have different feeding habits and spatial distribution, what makes them very appealing for a polyculture system. Dry extruded feed was offered twice a day for tilapias only, which represented the input of allochthonous organic matter. The experimental design was completely randomized with four replications and three treatments: (1) without substrate; (2) with substrate made of geotextile blanket; (3) with substrate made of bamboo. It was collected samples of water from ponds and rain, sediment, feed, periphyton, gas (dissolved in the water and released from sediment), and stocked and harvested animals to determine the carbon, nitrogen and phosphorus content. Thus, will be possible to determine those elements in each compartment biosystem. After the trial period ended, will be conducted analyzes of samples and then analyzing the data.