This work was carried out during one year in a fish pond to evaluate the effect of water quality in a plankton community according to the adopted management. High densities of Euglenophyceae, Chlorophyceae and Cyanobacteria were associated with high nitrate levels (1 to 210 mg.L-1). Cell densities of Cyanobacteria over 90 ind.m³ × 10³ (85.5%) occurred when nitrate concentrations approximated 210 mg.L-1, total phosphorus less than 160 mg.L-1 and temperature above 25 °C. High density of Rotifera was associated with high density of Cyanobacteria (December). Only Trichocerca sp. among the Rotifera species was constant in all sampled sites, whereas Diaphanosoma birgei, ranging between 4 and 342 ind.L-1 (0.7 and 2.4%) during the study period, was the most representative among the Cladocera species. Results show that water quality management in the fish pond had a direct influence on the plankton population due to the shallowness of the environment, large nutrient discharges through feed, fertilizing, fish waste. In fact, they contribute towards the appearance of undesirable plankton organisms.

Aim: The objective of this study was to analyze the composition of phytoplankton and zooplankton communities related to the dynamics of a fish farm; Methods: Samples were collected every other day, within a period of twenty consecutive days, during the dry and rainy seasons. Two samples were collected upstream from the fish pond (reservoir); the other four samples were collected in the fish farm area; Results: Rotifera and Chlorophyceae species were found in high densities at almost all sampling sites during both seasons under analysis. The higher phytoplankton species richness from site P3 to P6 was influenced by the management employed within the fish farm. The zooplankton community showed low values of density, species richness and equitability during the dry season; Conclusions: The continuous water flow and the addition of fertilizers (organic and inorganic) in the fish ponds had an influence on the plankton community, leading to a reduction in water quality and Cyanobacteria dominance

Growth rate and medium parameters between two bench scale volumes (13-L and 250-L) were compared. Experiments were maintained batch mode and culture parameters were periodically measured during a 13-day period. Culture growth during the cultivation of algae Haematococcus pluvialis was determined qualitatively by cell counting, optical density, dry weight, ash content, amount of chlorophyll-a, total organic carbon content and by direct measuring of medium nutrients and some abiotic aspects. Vegetative cell growth was higher when cultured in 13-L with 1.33 x 10⁵ cells.mL⁻¹ on the 12^th day than when cultured in 250-L. Significant difference (p < 0.05) in the biology and water culture of H. pluvialis, with the exception of dry weight, ash, nitrite and ammonia, was reported between the volumes. Data obtained in current study for the upscale culture maintenance of H. pluvialis in laboratory conditions shows that it should be undertaken in a 13-L volume due to a greater time span of cells in a vegetative state, greater cell density, lipids and chlorophyll-a contents. Light was of paramount importance on the direct performance of H. pluvialis on the algal biological conditions.

A laboratory culture of Ankistrodesmus gracilis algae was evaluated by studying the biology of the species and its chemical composition in a traditional medium (CHU₁₂) and in two alternative culture media, NPK (20-5-20) and macrophyte (Eichhornia crassipes) + NPK, in three different types of recipients (fiberglass, carboy and plastic bag). First peak in the growth curve of Ankistrodesmus gracilis occurred on the ninth day in macrophyte + NPK medium (74.16 x 10⁵ cells mL^-1) in a fiberglass recipient. However, highest density (p < 0.01) was reported in medium CHU₁₂ (122.87 x 10⁵ cells mL^-1) in a plastic bag on the twelfth day. Cell density was over 70 x 10⁵ cells mL^-1 starting on the twelfth day. Growth rate of A. gracilis was similar (p > 0.05) in culture media in the three recipients. Protein and fiber were similar (p > 0.05) in the treatments, but lipids were higher (p < 0.05) in NPK. Nitrate, ammonia, total phosphorus and orthophosphate contents were over 1 mg L^-1 in NPK (p < 0.01). Results show that alternative media, such as NPK and macrophyte + NPK, are possible for large-scale culture of A. gracilis cultured in three types of recipients. Costs are low, occupying less space when cultured in plastic bags and in the laboratory.

Diversas são as atividades antrópicas que disponibilizam resíduos e rejeitos nos ecossistemas, principalmente os aquáticos, e geralmente de forma inadequada. Como resultado, pode-se haver incrementos da quantidade de nutrientes, principalmente de fósforo e nitrogênio, tornando um meio propício para florações de Cyanobacteria. Objetivou-se com esse estudo identificar a comunidade fitoplanctônica e nutrientes da água em um braço do Rio Grande, Frutal, Minas Gerais, para verificar a possibilidade de uso da água na irrigação de cultivo agroecológico de olerícolas. Nos três pontos amostrais as variáveis temperatura, condutividade, oxigênio dissolvido e pH estavam em conformidade com a CONAMA 357/2005. Os nutrientes (fósforo total, ortofosfato, nitrato, nitrito e nitrogênio amoniacal total) apresentaram baixas concentrações e mantiveram-se em conformidade com a resolução em todos os pontos e períodos analisados. A abundância do fitoplâncton ficou dividida em 3 grandes grupos: Bacillariophyceae, Chlorophyceae e Cyanobacteria. Grandes quantidades de cianobactérias foram observadas nas amostras, trazendo risco devido ao potencial dessas algas para produzir toxinas. Para ser utilizada na irrigação de cultivo agroecológico, é necessário que a água em questão passe por tratamento.

Aim Examining whether small-scale tilapia cages have a potential influence on water abiotic parameters in a pond of a flow-through system. Methods Tilapia cages were installed near the pond water outlet. Samples for determination of abiotic parameters were monthly collected during eight months at five sampling sites: near three inlets receiving effluents from other fishponds (IW12, IW6 and IWM, the latter opening in a macrophyte bed), close to the cages in the open-pond (CC) and close to the water outlet (WO). The data were analyzed using Principal Component Analysis (PCA). Results The first PCA axis (70% of the data variability) was related to eutrophication and the second axis (20%) to the dependence of nitrifying bacteria on substrate availability. The sampling sites IW12, CC and WO showed high eutrophication levels. The lowest total phosphorus content, total suspended solids, hardness, alkalinity and conductivity and the highest dissolved oxygen were observed in the macrophyte bed area (IWM). Fish cages significantly increased total phosphorus content, conductivity, alkalinity and hardness in relation to the macrophyte bed inlet. Water outlet abiotic parameters were similar to near cage water. Conclusion The integrated cage-pond technology may be utilized in flow-through systems if incoming water quality (mainly in the site W12) is improved. Cages should be positioned closer to the pond center where it is deeper allowing higher flow-through and dispersion of uneaten feed residues and feces from the cages. This would avoid their deposition beneath cages and reduce their negatives influence on water quality entering the next fishpond (WO), and therefore not impair fish performance.