不同浓度氨氮对5种沉水植物生长的影响

通过试验研究,筛选出能够耐受高浓度氨氮的沉水植物,构建有效的生态系统并改善湖泊水质,对黑臭水体治理具有现实意义。探讨了苦草(Vallisneria natans)、穗花狐尾藻(Myriophyllum spicatum)、黑藻(Hydrilla verticillata)、金鱼藻(Ceratophyllum demersum)和小茨藻(Najas minor)5种沉水植物对氨氮的耐受性,每种沉水植物均设置氨氮浓度为0、4、8、12、16 mg/L共计5个梯度,研究其生长情况和生理指标的变化。结果显示,在4～16 mg/L氨氮持续胁迫至第14天时,苦草叶绿素和可溶性蛋白的生成受到抑制作用逐渐加大,4、8、12、16 mg/L氨氮试验组中的叶绿素含量与对照组相比,第14天比第7天分别减少44%、57%、16%和39%,可溶性蛋白含量分别减少62%、24%、29%和49%,而MDA含量在第14天分别显著降低为第7天的35%、7%、65%和41%,表明苦草未受到不可逆伤害。在4 mg/L氨氮持续胁迫下,第14天时,穗花狐尾藻和黑藻的MDA含量分别显著增加为第7天的207%和178%,小茨藻植株死亡,而金鱼藻的叶绿素和可溶性蛋白均未有显著变化,且MDA含量显著减少为第7天的80%,表明只有金鱼藻未受到氨氮的不可逆毒害。在8～16 mg/L氨氮持续胁迫下,穗花狐尾藻、黑藻、小茨藻和金鱼藻的植株则全部死亡。研究表明,氨氮浓度≤4 mg/L时,苦草和金鱼藻能够生长;氨氮浓度≤16 mg/L时,苦草能维持较长时间的生存。从耐氨氮和黑臭水体治理过程水质特征考虑,苦草可作为黑臭水体治理中水生态系统构建的先锋沉水植物。

Effect of Ammonia Nitrogen Concentration on the Growth of Five Submerged Vegetation Species

Aquatic plants play an important role in maintaining the health of aquatic ecosystems and submerged plants are the most sensitive to environment stress. Investigation of submerged vegetation tolerance to ammonia nitrogen (NH4+-N) is necessary for selecting plants to treat water bodies with black, odoriferous sediments. This study explored the morphological and physiological changes of five common submerged plants (Vallisneria natans, Myriophyllum spicatum, Hydrilla verticillata, Ceratophyllum demersum and Najas minor) under different concentrations of NH4+-N and selection of the pioneer species most appropriate for restoring black, odoriferous water bodies based on tolerance to ammonia. A control (no added ammonia) and four NH4+-N treatments (4, 8, 12 and 16 mg/L) were set. The experiment lasted 15 days (August 23 to September 7, 2017) with 20 plants in each trial, except for Ceratophyllum demersum trials in which 15 plants were used. Plant growth was recorded during the experiment and the wet weight of each plant was measured before and after the trials. On day 7 and 14, the chlorophyll, soluble protein and MDA contents of leaves were determined in triplicate for each species. The chlorophyll, soluble protein and MDA contents of Vallisneria natans decreased at all treatment levels. From day 7 to day 14, at the four NH4+-N concentrations (4, 8, 12 and 16 mg/L), the respective decreases in leaf content were as follows: chlorophyll (40%, 58%, 12% and 30%); insoluble protein (104%, 32%, 43% and 74%); and MDA (35%, 7%, 65% and 41%). These values indicate that the Vallisneria natans plants were not irreversibly injured. At 4 mg/L NH4+-N, all the Najas minor plants died and the MDA content of Myriophyllum spicatum and Hydrilla verticillata increased significantly (207% and 178%) from day 7 to day 14. Also at 4 mg/L NH4+-N, the MDA content of Ceratophyllum demersum decreased by 20%, with no evident changes in chlorophyll and soluble protein. In the 8-16 mg/L NH4+-N treatments, plants of all species died, except for Vallisneria natans. In summary, Ceratophyllum demersum survived at 4 mg/L NH4+-N and Vallisneria natans survived at all treatment levels. Thus, Vallisneria natans is recommended as the pioneer submerged aquatic vegetation species for restoration of aquatic ecosystems suffering from black, odorous sediment.