Variation characteristics of CO2 flux and their impact on freshwater aquaculture pond at multi-temporal scales
In order to investigate variation characteristics of CO2 fluxes at multi-temporal scales and identify their impact factors,high-frequency CO2 flux was continuously measured by the eddy covariance method from 2016 to 2021 in typical freshwater aquaculture ponds in the Yangtze River Delta,China.By using these data,the multi-temporal variation characteristics of CO2 flux and its environmental and anthropogenic factors were analyzed.The results clearly showed daily,seasonal and interannual variations in CO2 flux.The annual amount of CO2 flux(calculated in C)ranged from-671 kg·hm-2·a-1 to 1 005 kg·hm-2·a-1 with an average value of(-74±688)kg·hm-2·a-1,indicating that the ponds were a weak CO2 sink.The main impact factors of CO2 flux at different temporal scales were not the same.At the half-hourly scale,solar radiation and air temperature controlled daytime and nighttime CO2 flux,respectively.At the daily and monthly scales,CO2 flux were regulated by solar radiation and normalized vegetation index(NDVI),respectively.Moreover,CO2 fluxes were negatively and significantly correlated with these factors.At the annual scale,the CO2 flux was influenced by both the amount of feed inputs and NDVI.The regression equation established by the two factors could explain 64%of the total annual CO2 flux variation.Furthermore,CO2 emissions increased linearly with the increase in feed inputs(R2=0.55,P<0.05).Based on this study,improving feed utilization efficiency is suggested as an important way to control greenhouse gas emissions from aquaculture ponds,improve the ecological environment of water bodies,and sustainably develop the aquaculture industry in the future.
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