Abstract:Light is an important environmental factor affecting the growth and development of aquatic animals, and its propagation characteristics in aquaculture waters are still unclear. In this experiment, five light emitting diode (LED) light sources were selected: red (peak at 645 nm), green (510 nm), blue (445 nm), UVA (355 nm), and full spectrum (the wavelength of white light emitted by blue light excited silicate phosphor can reach λ400~800 nm). The radiation irradiance was adjusted to 60 W/m2, and the propagation law of irradiance was studied under different breeding water quality environments to provide references in order to meet the photobiological requirements of indoor factory aquaculture and the standardization control of aquaculture environment. The experimental results showed that the transmittance of five different LED light sources decreases with the increase in water depth. The variation trends of different light sources were different. When the water depth was 10 cm, the green light showed the largest transmittance (46.01%±4.03%), whereas UVA showed the lowest value (26.01%±2.53%). When the water depth was 150 cm, the light transmittance of all five light sources was less than 1.5%. The attenuation curves of light transmittance in water of five different light colors all agree with power function. The absorption of LED lights by water was discrepant in different spectral regions and has obvious selectivity. Most of the infrared and ultraviolet parts of the spectrum were absorbed by water. The absorption of the red, yellow, and green spectra in the visible spectrum band is also significant. LED light is severely attenuated in aquaculture water, and water depth is the main factor affecting LED light propagation (P<0.01), followed by total suspended solids (TSS) and chemical oxygen demand (COD). However, the extent to which different light sources are affected by TSS and COD content in aquaculture water varies. The attenuation of light in water is caused by the absorption and scattering of light by water, and the attenuation rate of light in different wave bands is mainly determined by the absorption spectrum of aquatic media.
