Several factors directly influence the formation and maintenance of bioflocs, such as the carbon/nitrogen ratio, oxygenation, carbon sources, light, etc. Light is considered an extremely important abiotic factor for organisms that live in the aquatic environment. Studies show significant differences in behavior, growth, food intake, maturation, reproduction, and possibly changes in swimming activity of peneid shrimp when exposed to different light conditions. For microorganisms, often especially when exposed to sunlight, it can change abruptly from a heterotrophic system (dominated by bacteria and protozoa mainly) to a predominantly photoautotrophic system (dominated by microalgae). This study aimed to evaluate the growth performance of Litopenaeus vannamei reared in a BFT system with supplementary colored LED light.
Five treatments were designed with 3 repetitions each, using colored LED lights, namely: yellow, blue, red, green and white. The experimental units were isolated from each other using a conical lid over the tanks, so that the influence of a color on the other would not occur. Animals weighing 0.37 g were stored at a stocking density of 500 shrimp/m³ in experimental units of 150 L. The experiment lasted for 70 days.
Significant differences were found for water quality parameters such as nitrite, light penetration into the water column and total amount of water used during culture period. No statistical differences were found for temperature, dissolved oxygen, pH, ammonia, nitrate, phosphate, alkalinity, CO2, total suspended solids, settleable solids, turbidity and chlorophyll a. The total amount of water used differ significantly, the colors of green, blue and red lights used lower amounts of water (340 liters), comparing with white and yellow lights (495 liters)(Figure 1). This difference in the total amount of water for production is related to the number of water exchange that were carried out when nitrite levels exceeded the safety levels for the specie (Figure 2). The color of green and blue light had better nitrification when compared to white light (control).
The present study demonstrated that the production of Litopenaeus vannamei exposed to green light showed significantly better results in water quality and zootechnical parameters when compared to other colors, we are currently analyzing the microbial community and oxidative stress in different treatments in order to elucidate these questions.