Photosynthetic response of Zostera japonicain Yellow River estuary to environmental stress

In this paper, we studied the effect of different combinations of light limitation caused by water turbidity and heavy metal contamination on Zostera japonica fluorescence properties through field monitoring and laboratory experiments, basing on the fact that the seagrass in the Yellow River estuary faces light limitation caused by water turbidity and heavy metal Cu pollution. Results showed that: 1) Under turbidity stress and coupled stress of turbidity and low heavy metals Cu concentrations, chlorophyll content of Zostera japonica blade reduced, photosynthetic pigment synthesis was inhibited. Ratio of chlorophyll a and chlorophyll b under both scenarios above was higher than it under coupled stress of turbidity and high heavy metals Cu concentrations, showing the content of light harvesting complexes is lower in the former. 2) Under environmental stress, qP value decreased, energy for electron transfer is reduced, reducing the light use efficiency; In short, Zostera japonica has a strongercompatibility to turbidity stress and is not sensitive to different turbidity gradient stress, however, it is affected by duration time of turbidity stress and stress scenarios. The effect of Heavy metal Cu on photosynthesis of Zostera japonica is greater than water suspended particles.