Response of phytoplankton to different carbon sources and C:N ratios in tilapia fingerling culture with bioflocs.

Abstract

The objectives of this study were to evaluate the dynamics and qualitative and quantitative aspects of the phytoplankton community during the fingerlings production of Nile tilapia (Oreochromis niloticus) using biofloc technology. A complete randomized design, with 6 treatments and 4 replications was used. Three carbon sources molasses (M), sugar (S) and cassava starch (CS) at carbon:nitrogen (C:N) ratios of 10:1 and 20:1 were evaluated. Phytoplankton was collected weekly during 63 days using 5 L water samples that were filtered through a 25 μm mesh plankton net. The phytoplankton community was represented by 17 genera of the Bacillariophyceae, Chlorophyceae, Cyanophyceae, Euglenophyceae, and Fragilariophyceae classes. Pseudanabaena and Synechococcus were the main genera responsible for the dominance of the Cyanophyceae class in all treatments. Chlorophyceae was the second most diverse class, whose main genera were Chlorella and Scenedesmus. Molasses at C:N ratio of 20:1 were the carbon source that most affected the phytoplankton development