Comparative Phosphorus Accumulation and Ca-P Content of Two Submerged Plants in Response to Light Intensity and Phosphorus Levels

Abstract

The micro-environment formed by the photosynthesis of submerged plants is conducive to the formation of CaCO3-P from co-precipitation of calcium and phosphorus in water, thereby permanently removing phosphorus from water to the bottom mud and avoiding secondary pollution after plants decay. However, CaCO3-P co-precipitation shows obvious specific-differences and environmental dependencies. In the present study, two different submerged plants, Myriophyllum aquaticum and Potamogeton crispus, were used as the research objects. Two variables, inorganic phosphorus level (0, 0.2, and 2 mg·L-1) and light intensity [66 μmol·(m2·s)-1 and 110 μmol·(m2·s)-1], were set. After cultivating for a week, the plant relative growth rate, plant total phosphorus, plant ash phosphorus, and Ca-P were measured to analyze the actual ability of phosphorus accumulation and clarify the effect of plant corruption on phosphorus increase in the water body. Results revealed that under various culture conditions, the relative growth rates (RGR) of P. crispus were significantly higher than those of M. aquaticum, and RGR reached the maximum at a P level of 2 mg·L-1 and a light intensity of 66 μmol·(m2·s)-1. The addition of inorganic phosphorus significantly affected plant ash phosphorus of the two plants (P. crispus 95.681%, M. aquaticum 85.432%), and the highest value of Ca-P content in the ash phosphorus of the two submerged plants appeared at a high phosphorus level. The total phosphorus in P. crispus was lower than that in M. aquaticum under various treatments, but the total ash phosphorus and Ca-P levels were higher than those in M. aquaticum. Consequently, M. aquaticum and P. crispus can effectively accumulate phosphorus during growth. However, the actual ability of P. crispus of removing phosphorus from water by the formation of CaCO3-P was higher than that of M. aquaticum at a P level of 2 mg·L-1.