Journal of Ecology and Rural Environment ›› 2017, Vol. 33 ›› Issue (5): 433-439.doi: 10.11934/j.issn.1673-4831.2017.05.007

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The Ecological Characteristics of Oenanthe javanica Floating Mats and Its Feedback to Pond Water Quality

ZHAO Wan-wan1, GUO Li-yun2, ZHOU Guo-qin2, WU Wei1,3   

  1. 1. Wuxi Fishery College, Nanjing Agricultural University, Wuxi 214081, China;
    2. Nanjing Fishery Science Institute, Nanjing 210036, China;
    3. Freshwater Fisheries Research Center/Key Laboratory of Fishery Eco-environment Assessment and Resource Conservation in Middle and Lower Reaches of the Yangtze River, Chinese Academy of Fishery Sciences, Wuxi 214081, China
  • Received:2016-07-11 Online:2017-05-25 Published:2017-05-25

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Abstract:

Oenanthe javanica was used to construct an artificial floating bed in aquaculture system of situ circulating ecological engineering. The focus of the research was to study the growth and the ecological characteristics of Oenanthe javanica, and to receive the response to pond water quality and environment. The research revealed that the average height, the dry weight and the root surface area of Oenanthe javanica increased constantly over the running 80 days. The plant grew rapidly and the overall heights were ranging from 23.05 to 38.37 cm in the period of 50 to 80 days. Moreover, the plant root system, which was assessed by measuring taproot number, root tip number, taproot diameter and lateral root diameter, was enhanced significantly in the 30th to 50th days. The nitrogen content of each plant was increased consistently with the increase of plant weight, and was high-positive correlated with its dry weight (r=0.952). While the phosphorus contents fluctuated between 3.45 and 4.14 mg, which were relatively stable. The average N/P ratios were from 2.51 to 6.80, and varied significantly in different parts of the plant. In addition, the N/P ratios of root variated from 4.27 to 4.67, which were more stable than those of the stems and leaves. The roots of Oenanthe javanica had the ability to reveal radial oxygen loss, and the rate of radial oxygen loss was ranging from 2.74 to 3.27 μmol·h-1·g-1. The rate of radial oxygen loss had a positive correlation with the surface area of root per gram (r=0.795). The O2 secretion of roots led to the oxidation of ferrous and reductive manganese the formation of oxide film around with ionic iron and manganese, and it reduced the contents of iron and manganese in the water, which affected the phosphorus absorption for the plants. Oenanthe javanica floating mats kept daily growth by using nutrients in the pond and gave relevant feedback on water ecological factors through their respective ecological characteristics simultaneously. Results show planted float system had the capacity to adjust the temperature, pH and dissolved oxygen in the water. What is more, it reduced total nitrogen and total phosphorus in the pond, and it had the limit of phosphorus removal. The study suggests the regeneration of plant roots and their corresponding properties play a vital role in the purification of water ecological environment.

Key words: floating-bed, Oenanthe javanica, water ecology, radial oxygen loss

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