The use of mechanical aeration and its effects on water mass

Abstract

Due to the increasing use of artificial aerators in fish ponds, and to the lack of studies on this subject, this work studied some of the aspects associated with their use. The influence of a diffuser type aerator (AR 120) on the biotic and abiotic variables was evaluated in a fish pond. Three points of the pond were marked for the taking of samples: 5, 10 and 23 m from the aerator. Samples were taken every day for 15 consecutive days: 5 days before the use of the aerator, 5 days with the aerator functioning and 5 days with it not functioning. The limnological variables studied did not show significant differences (P > 0.05) when the three sampling points were compared, but regarding the use of the aerator, variables such as water temperature, transparency, pH, dissolved oxygen, bicarbonate, free CO 2 , total phosphorus, orthophosphate, ammonia nitrate and nitrite concentrations showed significant differences (P < 0.05) when the water was mechanically agitated. There were no significant differences (P > 0.05) with the use of the aerator regarding conductivity, alkalinity, total CO 2 and chlorophyll a values. The phytoplanktonic community suffered as a direct influence of the aerator (P < 0.05). The community was dominated by Chlorophyta, representing more than 70% of the total organisms present, followed by Cyanophyta and Chrysophyta which tended to increase in number after the use of the aerator. This probably occurred because these groups adapt quickly to changes in the environment.Key words: mechanical aeration, limnological characteristics, pond. RESUMO Utilização da aeração mecânica e seu efeito na massa de águaDevido ao crescente aumento do uso de aeradores artificiais em sistema de cultivo de peixes e à carência de estudos nesta área, este trabalho avaliou a influência de um aerador tipo "propeller diffuser" (AR 120) nas variáveis bióticas e abióticas em um viveiro de engorda de peixe. Foram demarcados três pontos de coleta localizados a 5, 10 e 23 m de distância do aerador, durante 15 dias consecutivos, sendo 5 dias antes do uso do aerador, 5 dias com o aerador ligado e 5 dias com o aerador desligado. As variáveis limnológicas estudadas não apresentaram diferenças significativas (P > 0,05) entre os três pontos de coleta, porém, em relação ao uso do aerador, variáveis como temperatura, transparência, pH, oxigênio dissolvido, bicarbonato, CO 2 livre, fósforo total, ortofosfato, amônia, nitrato e nitrito diferiram significativamente (P < 0,05) com a agitação mecânica da água. Já a condutividade, alcalinidade, CO 2 total e clorofila a não apresentaram diferenças significativas (P > 0,05) com o uso do aerador. A comunidade fitoplanctônica sofreu influência direta do aerador (P < 0,05), dominada pelas Chlorophyta, representando mais de 70% do total de organismos presentes, seguidas das Cyanophyta e Chrysophyta, porém estas últimas tenderam a aumentar após o uso do aerador, uma vez que estes grupos se adaptam rapidamente às mudanças do ambiente. Palavras

Performance of Azolla caroliniana Willd. and Salvinia auriculata Aubl. on fish farming effluent

“…Decrease of phosphate would be due to plant absorption and perhaps due to algae proliferation in the effluent without plants. However, phosphate showed a slight increase after 30 days, which possibly occurred due to decomposition of organic material and death of algae (Sipaúba-Tavares et al, 1999b).…”

TINGKAT TRANSFER OKSIGEN KINCIR AIR SELAMA PERIODE BLIND FEEDING BUDIDAYA INTENSIF UDANG PUTIH (Litopenaeus vannamei)

“…Nilai salinitas yang optimum untuk menghasilkan tingkat standart transfer oksigen yang paling maksimum adalah sebesar 30 ppt [46]. Sedangkan stratifikasi nilai suhu di kolam disebabkan oleh proses agitasi dan turbulensi akibat percikan kincir air yang dinamis [39].…”