Abstract: Distribution of light spectrum and primary production in the waterbody of Meiliang Inlet of Taihu Lake was studied. The results show that on the water surface, the intensity of UV-C was low (10 ^-5 μE·m ^-2 ·s ^-1 ), that of UV-B increased with wavelength and that of UV-A was much higher (10 ^-2 μE·m ^-2 ·s ^-1 ) but attenuated rapidly with maximum vertical diffuse attenuation coefficient ( K _d )value up to 12.5 m ^-1 . K _d of visible light could reach as high as 8.2 m ^-1 . In comparison with the value on the surface, the intensity of ultraviolet at 0.5 m was less than 1%, and of visible light around 20%. The primary production was relatively low in the surface, reached peak at the depth of 0.2 m and then decreased with the increase in depth. Direct measurement revealed that dissolved oxygen in the water was high at the depth of 0.2 m. Concentration of chlorophyll-a varied with light intensity in the water. These results show that the distribution of primary production was the result of the joint effect of ultraviolet and visible light.

Key words: waterbody, ultraviolet spectrum, visible light spectrum, primary production