Phytoplankton community structure in Nile tilapia fish pond

Aim: This article is intended to identify which phytoplankton species can be biological descriptors and evaluate the dynamics of this community during the final stage of Nile tilapia ( Oreochromis niloticus ) growth, linking it to the production management method and to limnological variables. Methods : Samples of the inlet water and of the fish pond were used for the limnological analysis and to evaluate the phytoplankton community structure. Results : It was observed an increase of 1.5 times in N and TSS concentrations and of 2 times in P concentrations when comparing the results from the inlet water sample with the fish pond water. During the production cycle (113 days), 134 taxa belonging to ten taxonomic classes were registered. Chlorophyceae (60 taxa) and Cyanobacteria (26 taxa) were the classes that presented more diversity and abundance of species. The largest biovolumes were recorded in the fish pond. Nanoplankton species were the most abundant and represented 35% of the descriptor species in the phytoplankton community in the fish pond. Conclusions : As a consequence of the farming method applied, the instability of the system related to the control of the hydraulic retention time favored the presence of small cellular dimension species. The decrease in air and water temperature recorded at the end of the fattening cycle probably favored the increase and maintenance of diatoms.