Qualidade da água e estrutura da comunidade fitoplanctônica em tanques de piscicultura sobre efeito de probióticos

Abstract

This study aims to evaluate the water quality and the phytoplankton community structure in pisciculture tanks under probiotics influence. The research was carried out at the Pisciculture Sector, Animal Science Department (MP/DZ/CCA/UFPB) in Areia PB. In this study, three experimental systems were used with three repetitions each, with one being the witness, one being fertilized water with nitrogen (N), phosphorus (P) and probiotic, and the last being without probiotic and but with the fertilized water with nitrogen and phosphorus. The probiotics were applied in the dilution of 1:10.000. Water samples were collected from tanks each 28 days to determine the physical and chemical parameters, and also to the qualitative and quantitative determination of the phytoplankton community. Data was analyzed using SAS statistical software. To establish the significance level of the variations between treatments, variance analysis (ANOVA) was used. When the averages between treatments differed statistically, the Duncan test was applied. It has been identified 84 taxa being from this total, 63 have been found in witness tanks, 61 in the tanks fertilized with probiotics, and 62 in the tanks fertilized without probiotics, which were distributed in six classes(Bacillariophyceae, Chlamydophyceae, Chlorophycae, Cyanophyceae, Euglenophyceae e Zygnemaphyceae). Regarding the species richness the largest contribution was the class Chlorophyceae, followed by Euglenophyceae, to all experimental systems not showing significant statistic differences (P>0,05). The described species with higher density values the Schroederia indica (48%) e Chlorella sp.(24%)--typical organisms from shallow eutrophic or hypertrophic environments-- stood out in the treatments. The species Trachelomonas vovlvocinas with high affinity for environments rich in organic matter, stood out in witness tanks and in tanks fertilized with probiotics. The species Scenedesmus quadricauda and Pediastrum tetras have been representative in tanks fertilized without probiotics, common species in highly enriched environments. The tanks fertilized with probiotics showed intermediate species among the witness tanks and the fertilized tanks without probiotics. The rate levels of DBO found in environments with probiotics had been reduced, the microbial compost weekly application enhanced the degradation of organic matter improving the water quality. Regarding fish development, although statistically significant differences among treatments did not occur, the higher values of fish development were observed in tanks fertilized with probiotic application.