The effect of underwater supplemental light on the growth of V.spinulosa Yan and the restoration process of water

Abstract

Submerged plants are often used in the ecological restoration of polluted water, and they have good water purifying effect. In the process of water restoration, submerged plants are faced with insufficient light due to high turbidity or water depth. Therefore, we proposed a new model of artificial light assisted submerged plants to purify water nutrients. In this paper, we investigated the effects of locations and light intensities on the growth of V.spinulosa Yan and its water purification effect. The results showed that the light location of the underwater supplemental light was more important than the light intensity. The top supplemental light may provide an excellent environment for algae on the water surface. Excessive algae or epiphytic microorganisms might prevent the V.spinulosa Yan from obtaining light. When the PAR= 109 μmol m−2 s−1, V.spinulosa Yan had a higher biomass (145.39 dw/m2) than before (65.2 dw/m2). When the PAR > 280 μmol m−2 s−1, the clonal reproduction of V.spinulosa Yan was reduced. The main effect of supplemental underwater light on the water restoration process was enhancing the photosynthesis of V.spinulosa Yan by changing ETRmax and Fv/Fm of V.spinulosa Yan leaves. It significantly increased V.spinulosa Yan biomass and improved dissolved oxygen. Improvement of the water environment possibly altered the microbial environment and promoted the removal of water nutrients.