中文关键词水体氮磷营养盐负荷苦草光合荧光特性 英文关键词water nitrogen and phosphorusnutrient loadingsVallisneria natansphotosynthetic fluorescence characteristics

作者	单位	E-mail
周裔文	江苏大学环境与安全工程学院, 镇江 212013 南京师范大学环境学院, 南京 210008	ahzhoull@hotmail.com
许晓光	南京师范大学环境学院, 南京 210008
韩睿明	南京师范大学环境学院, 南京 210008
周晓红	江苏大学环境与安全工程学院, 镇江 212013	xhzhou0214@163.com
冯德友	江苏大学环境与安全工程学院, 镇江 212013
李致春	南京师范大学环境学院, 南京 210008
王国祥	南京师范大学环境学院, 南京 210008

中文摘要 以沉水植物苦草（Vallisneria natans）为对象，通过室内控制实验，研究营养盐负荷对苦草净化水体氮磷能力的影响；利用水下饱和脉冲荧光仪（Diving-PAM）研究营养盐负荷对苦草光合荧光特性的影响.结果表明，在本实验设置的氮磷浓度范围内（TN ≤ 12 mg ·L^-1，TP ≤ 1.0 mg ·L^-1），随营养盐浓度的升高，苦草对水体氮磷的净化能力逐渐增强：在高浓度营养盐组（TN=12 mg ·L^-1，TP=1.0 mg ·L^-1），水体氮磷去除率可达95%以上，当铵态氮含量较高时，苦草优先吸收铵态氮；中高浓度营养盐组（TN：8~12 mg ·L^-1，TP：0.6~1.0 mg ·L^-1）对苦草叶片F_v/F_m无显著影响；低浓度营养盐组（TN=3 mg ·L^-1，TP=0.3 mg ·L^-1）能够提高苦草叶片的F_v/F_m，有利于苦草生长.在本实验条件下，水体氮磷营养盐浓度越高，对苦草叶片的光合活性和光耐受能力抑制作用越明显；随着水体营养盐逐步下降，苦草叶片的光合活性逐渐恢复，捕光能力无明显变化. 英文摘要 Submerged macrophytes are an important component of aquatic ecosystems. During the growing period, submerged macrophytes can absorb nitrogen and phosphorus nutrients to reduce pollution loadings. Shoots of submerged macrophytes can also promote the adhesion of suspended substances in water, reducing the turbidity. The release of nutrients in sediments can be suppressed by its root system, and the resuspension of sediments caused by disturbance of winds and waves can also be resisted. The role of submerged macrophytes in ecological restoration of eutrophic lakes has attracted widespread attention. In 1960, the submerged plants Vallisneria natans and Potamogeton malaianus had been the dominant species in East Taihu. However after 2002, Nymphoides peltatum, Elodea nattalii, P. malaianus, etc. have gradually taken over the dominant roles along with significant elevations of nitrogen and phosphorus levels. Nutrients in water are not the only key factors causing eutrophication of water bodies; the nutrient source for submerged plant growth affect both the purification efficiency and the photosynthetic characteristics of submerged macrophytes. Excessive nitrogen and phosphorus concentrations can inhibit the photosynthetic physiological activities of submerged macrophytes, affecting the succession of aquatic vegetation. In addition, under high nutrient conditions, the competition from periphytic algae and planktonic algae may also directly poison submerged macrophytes, leading to its degradation and disappearance. Systematic studies on the regulation and photosynthetic fluorescence response mechanism of submerged macrophytes to varied nutrient loadings are helpful in revealing their relationships. The seedlings of submerged macrophyte V. natans were transplanted in a laboratory mesocosm to study the effect of nutrient loadings on its regulation of water nitrogen and phosphorus. Three nitrogen and phosphorus loadings from low, medium, and high levels derived from nitrate, ammonium, and phosphate were setup as the aquatic medium for the plant growth. Twelve harvests were carried out to determine the evolution of nutrient removal performance of V. natans. Its photosynthetic fluorescence characteristics were measured by a pulse-amplitude modulated fluorometer (Diving-PAM). Results showed that the nitrogen and phosphorus adsorption abilities of V. natans were gradually enhanced with the increase of nutrient concentrations in the range of TN ≤ 12 mg·L^-1 and TP ≤ 1.0 mg·L^-1. In the treatment of high nutrient concentrations (TN=12 mg·L^-1 and TP=1.0 mg·L^-1), the removal rates of nitrogen and phosphorus reached more than 95%. V. natans preferentially absorbed ammonium nitrogen when its concentration was high. The medium nutrient concentrations (TN:8-12 mg·L^-1 and TP:0.6-1.0 mg·L^-1) did not significantly affect the F_v/F_m ratio of leaves. However, the low nutrient concentrations (TN=3 mg·L^-1 and TP=0.3 mg·L^-1) could improve the F_v/F_m ratio of leaves and were beneficial for the growth of V. natans. The inhibition of photosynthetic activity and light tolerance were enhanced with the increase in nutrient concentrations. The photosynthetic activity of V. natans gradually recovered with no significant changes in the capacity for light harvesting, when the nutrient concentrations gradually decreased in the water. Our results indicate that the high nitrogen and phosphorus loadings indeed hamper the photosynthetic capacity, which may subsequently restrain the maintenance of the dominance of V. natans in the submerged macrophyte communities.

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