Oxygen depletion and the response of organic matter in Laoyehai, a lagoon with strong aquaculture activities

doi:10.3969/j.issn.1000-5641.2021.02.009

Abstract

Abstract:

Laoyehai is a lagoon located on the east coast of Hainan and is impacted heavily by human activities (especially those related to aquaculture). Laoyehai is characterized by its eutrophic and hypoxic waters. During previous dry and flood seasons (specifically, April 2010 and August 2011), when hypoxia occurred, field work was conducted to observe the dissolved oxygen (DO) and to collect organic matter. Hypoxia was significant in the spring season with surface DO as low as 50%, while the bottom hypoxic water prevailed in both seasons. In the spring season, the C/N ratio of particulate organic matter was higher than that observed in the summer season (C/N in the spring: 9.7, C/N in the summer: 7.7). Organic matter composition indicated by amino acids showed that there was strong in situ production in the spring relative to that in the summer. Lower C/N values and higher carbon and nitrogen yields of amino acids (AA C yield, AA N yield) in the summer showed active in situ production, suggesting that organic matter was mainly derived from phytoplankton. This also explains the sufficient surface DO in the summer. The degradation of particulate organic matter increased with the decrease of dissolved oxygen, indicating that the particulate organic matter and its degradation were the key driving factors for oxygen consumption in the lagoon. Meanwhile, we found that the relationship between dissolved organic matter components and DO was not significant.

Key words: Laoyehai, lagoon, hypoxia, organic matter, amino acid

CLC Number:

P593

Wenchao MA, Yan WANG, Zhuoyi ZHU. Oxygen depletion and the response of organic matter in Laoyehai, a lagoon with strong aquaculture activities[J]. Journal of East China Normal University(Natural Science), 2021, 2021(2): 85-99.

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氨基酸		氨基酸指征参数
英文缩写	中文名	英文缩写	中文名
THPAA	颗粒态氨基酸	AA C yield	氨基酸的碳归一化产量
THDAA	溶解态氨基酸	AA N yield	氨基酸的氮归一化产量
Asp	天冬氨酸	DI	降解指数
Glu	谷氨酸	D-AA%	D型氨基酸在总氨基酸中的比例
Asn	天冬酰胺	Gly%	甘氨酸在总氨基酸中的比例
Ser	丝氨酸	D/L-Ala	D型丙氨酸与L型丙氨酸的比值
Gln	谷氨酰胺
Thr	苏氨酸
Gly	甘氨酸
Arg	精氨酸
Ala	丙氨酸
GABA	γ -氨基丁酸
Tyr	酪氨酸
Aba	氨基丁酸
Val	缬氨酸
Met	蛋氨酸
Trp	色氨酸
Phe	苯丙氨酸
ILE	异亮氨酸
Leu	亮氨酸
Lys	赖氨酸

		温度/℃	盐度	pH值	DO/(mg·L^–1)	DO%	AOU/(mg·L^–1)
2010.4 表层	max	30.1	33.0	9.28	13	164%	3.8
	min	27.0	13.8	7.92	3	38%	–6.0
	mean	28.5	23.5	8.42	7	86%	0.1
2011.8 表层	max	34.1	27.5	8.51	9	128%	3.1
	min	29.9	7.2	7.42	4	49%	–2.4
	mean	31.9	16.5	8.05	6	90%	0.2
2010.4 底层	max	29.6	33.0	8.92	8	101%	6.8
	min	27.1	18.8	7.68	0.2	2%	–0.7
	mean	28.1	24.8	8.22	4	50%	2.9
2011.8 底层	max	32.1	32.3	8.21	6	81%	6.6
	min	30.1	16.4	7.45	0	0%	0.7
	mean	31.1	21.7	7.85	3	46%	3.2

		TSM/(mg·L^–1)	POC%	PN%	POC/(μmol·L^–1)	PN/(μmol·L^–1)	C/N
2010.4	max	42	14%	1.5%	434	40	11.7
	min	24	2%	0.3%	41	6	7.3
	mean	34	6%	0.7%	172	17	9.7
2011.8	max	60	4%	0.6%	129	16	8.4
	min	17	1%	0.2%	19	3	6.6
	mean	36	3%	0.4%	78	10	7.7

		THPAA						THDAA
		CONC/ (mg·L^–1)	AA C yield	AA N yield	DI	D-AA%	D/L-Ala	Gly%	CONC/ (mg·L^–1)	DI	D-AA%	D/L-Ala	Gly%
2010.4表层	max	5.9	16%	30%	0.7	7.4%	0.14	14%	3.2	5.1	16%	0.75	50%
	min	0.2	1%	3%	– 0.2	5.1%	0.03	6%	0.3	– 0.4	0%	0.13	38%
	mean	1.3	4%	9%	0.3	6.1%	0.09	10%	2.1	1.2	8%	0.25	44%
2011.8表层	max	2.4	10%	22%	1.9	11.3%	0.06	13%	3.4	3.4	10%	0.39	48%
	min	0.1	2%	4%	0.2	4.4%	0.05	8%	0.4	– 0.7	0%	0.25	34%
	mean	1.2	6%	13%	0.9	8.4%	0.05	9%	1.5	1.4	5%	0.31	40%
2010.4底层	max								3.3	1.1	11%	0.67	73%
	min								0.2	– 2.3	5%	0.11	42%
	mean								1.8	– 0.2	8%	0.25	50%
2011.8底层	max								1.5	1.6	11%	0.51	41%
	min								0.1	0.8	9%	0.26	36%
	mean								1.0	1.2	10%	0.34	39%

		AA C yield	AA N yield	THPAA				THDAA
		AA C yield	AA N yield	L-Glu%	L-Asp%	L-Ala%	Gly%	Gly%	L-Ala%	L-Asp%	L-Thr%
2010.4	内湾（网箱养鱼）	5%	13%	14%	13%	12%	9%	44%	11%	8%	6%
2010.4	外湾（岸滩养虾）	8%	16%	7%	8%	13%	9%	39%	9%	10%	5%
2011.8	内湾（网箱养鱼）	2%	4%	13%	14%	12%	11%	52%	7%	6%	4%
2011.8	外湾（岸滩养虾）	3%	6%	7%	9%	13%	9%	40%	9%	8%	5%