Greenhouse gas emissions from managed freshwater wetlands under intensified aquaculture

Qian Yue; Kun Cheng; Jing Sheng; Lei Wang; Chunying Ji; Yuefang Zhang; Jufeng Zheng; Qian Yue; Kun Cheng; Jing Sheng; Lei Wang; Chunying Ji; Yuefang Zhang; Jufeng Zheng

doi:10.48130/SSE-2023-0003

Figures (4) Tables (6)

Figure 1.
Temporal variation of environmental temperature and precipitation at the experimental sites.
Figure 2.
Diurnal variation of CO₂, CH₄ and N₂O fluxes for (a) CW_IA, (b) CW_EA, (c) EW_IA, (d) NW. D1, D2 and D3 for CW_IA were October 16, November 3 and December 9 with daily mean temperature ranging from 21.3 to 9.0 °C; D1, D2 and D3 for CW_EA were September 4, September 7, and September 22 with temperatures ranging from 29.7 to 23.1 °C; D1, D2 and D3 for EW_IA were September 21, September 22, and October 14 with temperatures ranging from 24.9 to 19.6 °C; D1, D2 and D3 for NW were November 4, November 20, and December 11 with temperatures ranging from 17.6 to 8.4 °C. GWP, the global warming potential.
Figure 3.
Seasonal GHG emission dynamics of (a) N₂O, (b) CH₄ and (c) CO₂ fluxes for different wetlands. The management practices of drainage and flooding occurred only to the sites of CW_IA, CW_EA and EW_IA.
Figure 4.
Dependence of CO₂, CH₄ and N₂O fluxes on feeding amount at the sites of (a) CW_IA and (b) EW_IA.

Sites	Origin	Area	Water table	Location		Feed	Forage content			Yield
Sites	Origin	(hm²)	m	Longitude	Latitude	Feed	Total C (g kg⁻¹)	Total N (g kg⁻¹)	C/N^*	t ha⁻¹ year⁻¹
NW	A natural lake	1,000	3−9	30.67°	117.52°	NA	NA	NA	NA	/
EW_IA	Wetland shifted to aquatic production	53	2−4	30.64°	117.46°	Fed on forage from March to October	127.12 ± 7.41	77.85 ± 2.03	1.6:1	11.32
CW_EA	Paddy converted constructed wetland with	2	1	30.73°	117.58°	Fed on wheat grain or grass or fertilizer irregularly				5.00
CW_IA	Paddy converted constructed wetlands with intensive aquaculture	2	1−2	30.66°	117.50°	Fed on forage from April to October	151.31 ± 2.80	72.39 ± 1.29	2.1:1	7.50
^* C/N represented the carbon-nitrogen ratio.

Table 1.

Basic information of the four experimental sites.

Sites	Cumulative emission			GHG emission intensity per kg product
Sites	N₂O-N (kg ha⁻¹)	CH₄-C (kg ha⁻¹)	CO₂-C (kg ha⁻¹)	N₂O (g kg⁻¹)	CH₄ (kg kg⁻¹)	Total (kg CO₂-eq kg⁻¹)
CW_IA	1.06 ± 0.20	457.08 ± 161.20	1,877.04 ± 527.95	0.22	0.10	3.25
CW_EA	0.81 ± 0.12	23.83 ± 7.80	1321.32 ± 91.11	0.25	0.01	1.21
EW_IA	2.43 ± 0.20	1,360.27 ± 1552.98	2,246.79 ± 488.23	0.34	0.19	5.30
NW	1.12 ± 0.42	38.29 ± 11.99	1,305.48 ± 216.63	/	/	/
/: represented no data. The values were presented as the mean ± standard deviation.

Table 2.

Cumulative CO₂, CH₄ and N₂O fluxes and yield-scaled GHG emission intensity for different wetland systems.

Sites GWP Contributions (%)
t CO₂-eq ha⁻¹ y⁻¹ N₂O CH₄ CO₂

CW_IA 24.38 2% 70% 28%
CW_EA 6.04 6% 14% 80%
EW_IA 60.02 2% 85% 14%
NW 6.67 7% 21% 72%

Table 3.
Global warming potentials and their contributions for different wetland systems.

Sites		pH	$ {\text{NH}^+_4}{\text {-N}}$ (mg L⁻¹)	${\text{NO}^-_3}{\text {-N}} $ (mg L⁻¹)	${\text{NO}^-_2}{\text {-N}} $ (mg L⁻¹)	TN (g L⁻¹)	DOC (mg L⁻¹)
Water quality	CW_IA	7.52 ± 0.14^a	0.60 ± 0.35^a	0.57 ± 0.26^b	0.48 ± 0.51^a	1.93 ± 0.69^ab	24.99 ± 8.50^ab
	CW_EA	7.39 ± 0.48^a	0.46 ± 0.33^a	0.36 ± 0.12^b	0.10 ± 0.16^ab	1.30 ± 0.52^bc	21.83 ± 7.67^ab
	EW_IA	7.50 ± 0.28^a	0.66 ± 0.61^a	1.36 ± 0.56^a	0.36 ± 0.49^ab	2.07 ± 0.88^a	29.93 ± 8.92^a
	NW	7.57 ± 0.29^a	0.25 ± 0.20^a	0.28 ± 0.08^b	0.03 ± 0.03^b	0.66 ± 0.23^c	20.01 ± 7.71^b

Sites		pH	$ {\text{NH}^+_4}{\text {-N}}\;{\rm{ (mg\; kg^{−1})}} $	$ {\text{NO}^-_3}{\text {-N}}\;{\rm{ (mg\; kg^{−1})}} $	SOM (g kg⁻¹)	TN (g kg⁻¹)	C/N
Sediment quality	CW_IA	6.81 ± 0.13^a	36.67 ± 4.32^b	273.70 ± 185.08^a	39.69 ± 2.75^ab	2.95 ± 0.18^ab	7.81 ± 0.51^ab
	CW_EA	6.22 ± 0.18^b	33.21 ± 6.39^b	54.57 ± 20.31^a	39.66 ± 4.16^ab	2.68 ± 0.19^b	8.58 ± 0.42^a
	EW_IA	6.59 ± 0.29^a	203.22 ± 16.08^a	251.03 ± 263.67^a	44.00 ± 1.15^a	3.34 ± 0.06^a	7.46 ± 0.19^b
	NW	6.58 ± 0.14^a	27.86 ± 5.07^b	21.23 ± 5.10^a	35.78 ± 4.09^b	2.91 ± 0.47^ab	7.00 ± 0.73^b
TN, DOC, SOM and C/N represented total nitrogen, dissolved organic carbon, soil organic matter and carbon : nitrogen ratio, respectively.

Table 4.

Water and sediment qualities at the four experimental sites.

Items		pH	DOC	${\text{NH}^+_4}{\text {-N}} $	${\text{NO}^-_3}{\text {-N}} $	${\text{NO}^-_2}{\text {-N}} $	TN	Water temperature
Correlation	CH₄	0.11	0.09	0.60^**	0.80^**	−0.17	0.13	0.46^*
	N₂O	0.31	0.20	0.37^*	0.60^**	−0.22	0.10	0.55^**
	CO₂	0.28	−0.11	0.70^**	0.54^**	−0.23	0.11	0.65^**
P value	CH₄	0.574	0.633	0.002	0.000	0.399	0.517	0.014
	N₂O	0.109	0.299	0.049	0.001	0.249	0.605	0.003
	CO₂	0.144	0.576	0.000	0.003	0.246	0.575	0.000
* Significant at P < 0.05; ** Significant at P < 0.01.

Table 5.

Correlation coefficients between GHGs emission and water parameters in all four wetlands.

Location		Sources	Time horizon	Wetland types	N₂O fluxes	CH₄ fluxes	CO₂ fluxes
Location		Sources	Time horizon	Wetland types	μg m⁻² h⁻¹	mg m⁻² h⁻¹	mg m⁻² h⁻¹
China	East China	Current study	13 months	Constructed wetland for intensive aquaculture	18.65 ± 20.48	6.92 ± 9.41	77.23 ± 68.95
				Constructed wetland for extensive aquaculture	14.08 ± 9.58	0.35 ± 0.45	51.21 ± 40.97
				Enclosure wetland for intensive aquaculture	41.89 ± 24.83	20.60 ± 19.90	90.34 ± 65.45
				Natural wetland	19.50 ± 12.48	0.55 ± 0.41	51.09 ± 33.48
	East China	Liu et al. (2016)	12 months	Rice paddies	110.5	0.71
	East China	Liu et al. (2016)	12 months	Crab-fish aquaculture	48.1	0.37
	Southeastern China	Yang et al. (2015)	5 months	Shrimp pond	10.74	19.95	20.78
	Southeastern China	Yang et al. (2015)	4 months	Shrimp-fish pond	11.8	1.65	−60.46
	Lab simulation of aquatic system	Hu et al. (2014)	2 months	Control	5,504 ± 1,221		2,401 ± 343
	Lab simulation of aquatic system	Hu et al. (2014)	2 months	Treatment	911 ± 488		4,590 ± 546
Overseas of Nature wetlands	Yangtze estuarine, China	Wang et al. (2009)	12 months	Marsh site		2.06
	Yangtze estuarine, China	Wang et al. (2009)	12 months	Bare tidal flat		0.04
	East China	Han et al. (2013)	3 months	Open river	62.17 ± 2.13	16.41 ± 3.06	162.18 ± 10.55
				Canal	111.74 ± 7.41	175.94 ± 18.42	1,082.00 ± 90.53
				Reservoir	50.99 ± 2.68	1.70 ± 0.14	25.61 ± 4.08
	Northeast China	Yang et al. (2013)	3 months	Freshwater marsh	13.3	8.92	394.5
	India	Selvam et al. (2014)	24 h/1−8 h	Ponds		11.93 ± 12.33	123.02 ± 117.33
				Rivers		4.13 ± 8.27	36.85 ± 70.58
				Reservoirs		2.13 ± 2.33	15.40 ± 35.75
	Colombia	Dennis et al. (2014)	11 months	Restored mangrove	162 ± 48	3.47 ± 1.52
					97 ± 46	11.78 ± 10.54
					747 ± 299	6.12 ± 9.69
	Costa Rica	Nahlik et al. (2011)	29 months	Forested marsh		5.05
				Rainforest swamp		33.39
				Alluvial marsh		39.94
	Australia	Allen et al. (2011)	6 months	Mangrove	30.00	0.30
	Orinoco River Floodplain, Venezuela	Smith et al. (2000)	17 months	Open river		1.33
				Flooded forest		4.67
				Macrophyte mats		1.33

Table 6.

Comparison of greenhouse gases fluxes from different wetland types with previous studies in China and other regions.

Sites	GWP	Contributions (%)
Sites	t CO₂-eq ha⁻¹ y⁻¹	N₂O	CH₄	CO₂
CW_IA	24.38	2%	70%	28%
CW_EA	6.04	6%	14%	80%
EW_IA	60.02	2%	85%	14%
NW	6.67	7%	21%	72%