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Fig. 2. Box plots of monthly values of (a) water-column PO?” concentration; and (b) pore-water CO concentrations. COz flux across the sediment—water interface (Fs.w) varied signifi- cantly with time (p < 0.001) and was always positive (i.e., CO2 going from sediment to water) (Fig. 4a). Fs.w was low in spring, between 0.25 During the shrimp farming period between May and November, farmers added animal feeds twice per day to the ponds. The amount of added feeds increase as shrimp grow. Unconsumed feeds and animal

Figure 2 Box plots of monthly values of (a) water-column PO?” concentration; and (b) pore-water CO concentrations. COz flux across the sediment—water interface (Fs.w) varied signifi- cantly with time (p < 0.001) and was always positive (i.e., CO2 going from sediment to water) (Fig. 4a). Fs.w was low in spring, between 0.25 During the shrimp farming period between May and November, farmers added animal feeds twice per day to the ponds. The amount of added feeds increase as shrimp grow. Unconsumed feeds and animal

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Fig. 1. Map of the Shanyutan wetland within the Min River estuary showing the aquaculture ponds used in this study. Three shrimp (Litopenaeus vannamei) ponds were selected for the study (Fig. 1). Each pond was ~1.5 m deep and had an area of 1.5-2.0 ha. Field sampling was carried out monthly from April 2019 to January 2020. Samples of sediment and water were collected from three different locations with each pond: one near the bank, one in the feeding zone, and one at the center of the pond (Tian et al., 2023). The upper 15 cm sediments were collected using a steel cylinder with a diameter of 5 cm then transferred into sterile plastic bags. For the water column samples, a 1.5-L organic glass hydrophore was utilized to collect samples from the surface layer (approximately 10 cm below the surface), mid-depth, and the bottom layer (around 5 cm above the sediment). The collected water samples were immediately divided into two portions. One portion of the water sample was transferred into a pre-weighed serum glass bottle (55 mL) without bubbles and preserved with 0.5 mL HgClz for the analyses
Fig. 1. Map of the Shanyutan wetland within the Min River estuary showing the aquaculture ponds used in this study. Three shrimp (Litopenaeus vannamei) ponds were selected for the study (Fig. 1). Each pond was ~1.5 m deep and had an area of 1.5-2.0 ha. Field sampling was carried out monthly from April 2019 to January 2020. Samples of sediment and water were collected from three different locations with each pond: one near the bank, one in the feeding zone, and one at the center of the pond (Tian et al., 2023). The upper 15 cm sediments were collected using a steel cylinder with a diameter of 5 cm then transferred into sterile plastic bags. For the water column samples, a 1.5-L organic glass hydrophore was utilized to collect samples from the surface layer (approximately 10 cm below the surface), mid-depth, and the bottom layer (around 5 cm above the sediment). The collected water samples were immediately divided into two portions. One portion of the water sample was transferred into a pre-weighed serum glass bottle (55 mL) without bubbles and preserved with 0.5 mL HgClz for the analyses
Summary of two-way ANOVAs examining the effects of water depth, month and their interactions on average Chl-a and dissolved CO2 concentrations in the water column of the aquaculture ponds.
Summary of two-way ANOVAs examining the effects of water depth, month and their interactions on average Chl-a and dissolved CO2 concentrations in the water column of the aquaculture ponds.
Fig. 3. Monthly water column concentrations of (a) chlorophyll-a and (b) dissolved CO at different water depths (mean + SE; n = 9). Numbers within panel b a seasonal average of rate of change in [CO2] with depth, based on linear regressions. See text and Table S1 for explanation.
Fig. 3. Monthly water column concentrations of (a) chlorophyll-a and (b) dissolved CO at different water depths (mean + SE; n = 9). Numbers within panel b a seasonal average of rate of change in [CO2] with depth, based on linear regressions. See text and Table S1 for explanation.
Fig. 4. Monthly diffusive COz flux across (a) sediment—water interface and (b) water-—air interface (mean + SE); and (c) seasonal apparent CO» consumption within the water column (mean + SE). See text for explanation.
Fig. 4. Monthly diffusive COz flux across (a) sediment—water interface and (b) water-—air interface (mean + SE); and (c) seasonal apparent CO» consumption within the water column (mean + SE). See text for explanation.
Fig. 5. Correlations among environmental and CO variables in (a) water column and (b) sediment. Wcoz2 is water-column CO, concentration and Fw-, is CO2 diffusive flux across the water-air interface. Pco2 is porewater CO2 concentration and Fs.w is CO2 diffusive flux across the sediment—water interface. Color of the box indicates the direction of correlation (blue = positive; red = negative); size of the box is proportional to the r* value. Asterisks indicate levels of significance (*p < 0.05; **p < 0.01; **p < 0.001). See main text for explanation of the abbreviations. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 5. Correlations among environmental and CO variables in (a) water column and (b) sediment. Wcoz2 is water-column CO, concentration and Fw-, is CO2 diffusive flux across the water-air interface. Pco2 is porewater CO2 concentration and Fs.w is CO2 diffusive flux across the sediment—water interface. Color of the box indicates the direction of correlation (blue = positive; red = negative); size of the box is proportional to the r* value. Asterisks indicate levels of significance (*p < 0.05; **p < 0.01; **p < 0.001). See main text for explanation of the abbreviations. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 6. Partial least square structural equation modeling (PLS-SEM) to evaluate the direct and indirect effects of environmental factors on (a) water CO2 concen- tration (Wco2) and CO diffusive flux across the water-air interface (Fw-a), and (b) sediment porewater dissolved CO2 concentration (Pco2) and CO2 diffusive flux across the sediment—water interface (Fs.w). Solid blue and red arrows indicate significant positive and negative effects, respectively, and dotted arrow indicates insignificant effect on the dependent variable. Numbers adjacent to arrows are standardized path coefficients, indicating the effect size of the relationship. R* represents the variance explained for target variables. * p < 0.05; ** p < 0.01. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 6. Partial least square structural equation modeling (PLS-SEM) to evaluate the direct and indirect effects of environmental factors on (a) water CO2 concen- tration (Wco2) and CO diffusive flux across the water-air interface (Fw-a), and (b) sediment porewater dissolved CO2 concentration (Pco2) and CO2 diffusive flux across the sediment—water interface (Fs.w). Solid blue and red arrows indicate significant positive and negative effects, respectively, and dotted arrow indicates insignificant effect on the dependent variable. Numbers adjacent to arrows are standardized path coefficients, indicating the effect size of the relationship. R* represents the variance explained for target variables. * p < 0.05; ** p < 0.01. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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