Variation in the Underwater Light Field under Simulated Water Current Conditions in Lake Taihu, China

ABSTRACT

Under simulated water current conditions, we investigated the effects of total suspended solids (TSS) and chlorophyll a (chl a) on the diffuse attenuation coefficient and euphotic depth in Lake Taihu water. Photosynthetically available radiation (PAR) diffuse attenuation coefficients [K_d (PAR)] ranged from 1 to 2 and 4 m⁻¹, with corresponding euphotic depths of 4.6, 2.3, and 1.15 m under still, slow, and fast water currents, respectively. The blue wavelength was the most strongly attenuated, and green was the most penetrating wavelength. The ranges of spectral diffuse attenuation coefficients from 400 to 700 nm were 0.75–2.56, 2.30–4.66, and 3.51 −10.34 m⁻¹ under the three water currents. Significant correlations were found between K_d (PAR), euphotic depth [Z_eu (PAR)], Secchi depth (SD) and TSS. However, TSS was the primary attenuation factor responsible for the observed differences in K_d , Z_eu, and SD under conditions of different water current.