Comparison Of Greenhouse Gases Fluxes Between Cyperus Malaccensis Marsh And Shrimp Pond In The Min River Estuary

In recent years,with the influence of market and land resource limitation,more and more coastal tidal marsh had been reclaimed into aquiculture ponds.Temporal variations of the CH₄ fluxes from the Cyperus malaccensis marsh ecosystem and at the water-air and sediment-air interfaces of the shrimp pond converted from C.malaccensis marsh were determined using static chamber and floating/static chamber technique from May 2016 to March 2017 in the Shanyutan wetland of the Min River estuary,Southeast China.The physical and chemical parameters of the water and sediment in the C.malaccensis marsh and the shrimp pond were measured simultaneously,and the sediment CH₄ and N₂O production potential of two sampling sites had been measured.The results show that:（1）The environmental factors all demonstrated the distinct dynamic characteristics from C.malaccensis marsh and shrimp pond.Shrimp pond nutrient concentrations such as DOC、TN、NO₃^--N、Cl^-and SO₄^2-were less than C.malaccensis marsh because of avoiding eutrophication in aquiculture period,and due to conversion from aquiculture period and drained period,environmental factors present stage characteristics.Compared with coastal tidal marsh,the physical and chemical parameters of the water column in shrimp pond were strongly managed by human culture.（2）The average values of CH₄ fluxes from the C.malaccensis marsh and the shrimp pond was（11.67± 1.99）mg·m^-2·h^-1 and（18.69± 4.84）mg.m^-2·h^-1,respectively,and ranged from 1.09～38.38 mg·m^-2·h^-1 and from 0.01～65.38 mg·m^-2.h^-1,respectively.In the culture period the CH₄ emissions from the shrimp pond was significantly higher than that in the C.malaccensis marsh,and increased 68.0%,but decreased 86.95%in drain period.The average values of N₂O fluxes from the C.malaccensis marsh and the shrimp pond was（18.51± 21.41）mg·m^-2·h^-1 and（77.13± 19.11）mg·m^-2·h^-1,respectively,and ranged from^-173.43-206.57 mg m^-2 h^-1 and from-9.07～284.59 mg·m2·h^-1,respectively.In the culture period and drain period the N₂O emissions from the shrimp pond was significantly higher than that in the C.malaccensis marsh,and increased 21.10%and 1195.91%,respectively.（3）Both C.malaccensis marsh and shrimp pond functioned as a source of atmosphere CH₄;There was a transformation between source and sink of atmosphere N₂O in C.malaccensis marsh,but shrimp pond functioned as a source of atmosphere N₂O.During the observation period,CH₄ and N₂O emission of shrimp pond was higher than C.malaccensis marsh by 60.20%and 316%,respectively.（4）In laboratory anaerobic incubation experiment,the sediment CH₄ production potential in C.malaccensis marsh(40.07 ng·g^-1·d^-1)was significantly higher than that of shrimp pond(2.16 ng·g^-1·d^-1,),the law of sediment CH₄ production potential in both of two sampling sites showed summer and autumn was higher than winter and spring.There was no significant difference of N₂O production potential between C.malaccensis marsh(0.61 ng g^-1·d^-1)and shrimp pond(0.58 ng g^-1·d^-1),the law of sediment N₂O production potential in two sampling sites showed spring and summer was higher than autumn and winter.（5）The average values of ecosystem respiration in the C.malaccensis marsh and CO₂ flux in the shrimp pond was（1642.28 ± 214.47）mg m^-2 h^-1 and（42.66 ± 18.12）mg·m^-2 h^-1,respectively.The average values of CO₂ flux in culture period and drain period from shrimp pond was（17.98 ±18.26）mg·m^-2·h^-1 and（78.51± 16.61）mg m^-2.h^-1,respectively.