Weicong Chen, Heng Sun, Zhongyong Gao, Jiaming Lin, Min Xu, Aijun Wang, Shuqin Tao. Carbonate system in the subtropical Jiulong River estuary and CO2 flux estimation under modulation of tidal cycle[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-0000-0
Citation:
Weicong Chen, Heng Sun, Zhongyong Gao, Jiaming Lin, Min Xu, Aijun Wang, Shuqin Tao. Carbonate system in the subtropical Jiulong River estuary and CO2 flux estimation under modulation of tidal cycle[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-0000-0
Weicong Chen, Heng Sun, Zhongyong Gao, Jiaming Lin, Min Xu, Aijun Wang, Shuqin Tao. Carbonate system in the subtropical Jiulong River estuary and CO2 flux estimation under modulation of tidal cycle[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-0000-0
Citation:
Weicong Chen, Heng Sun, Zhongyong Gao, Jiaming Lin, Min Xu, Aijun Wang, Shuqin Tao. Carbonate system in the subtropical Jiulong River estuary and CO2 flux estimation under modulation of tidal cycle[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-0000-0
Key Laboratory of Global Change and Marine Atmospheric Chemistry, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China
2.
School of Marine biology, Xiamen Ocean Vocational College, Xiamen 361100, China
3.
Laboratory of Coastal and Marine Geology, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China
4.
Fujian Provincial Key Laboratory of Marine Physical and Geological Processes, Xiamen 361005, China
5.
Observation and Research Station of Island and Costal Ecosystem in the Western Taiwan Strait, Ministry of Natural Resources, Xiamen 361005, China
Funds:
The Scientific Research Foundation of Third Institute of Oceanography, MNR under contract Nos. 2022001, 2020017, 2023008 and 2019018; Natural Science Foundation of Fujian Province of China under contract No. 2023J01209; National Natural Science Foundation of China under contract No. 4237061213; Fujian science and technology innovation leader project.
Estuaries are often a significant source of atmospheric CO2. However, studies of carbonate systems have predominantly focused on large estuaries, while smaller estuaries have scarcely been documented. In this study, we collected surface and bottom seawater carbonate samples in the subtropical Jiulong River estuary across different tidal levels from 2019 to 2021. The results showed that estuarine mixing of freshwater from the river with seawater was the dominant factor influencing the estuarine carbonate system. Moreover, estuarine mixing is concomitantly impacted by the net metabolism of biological production and decomposition, groundwater input, release of CO2 from the estuary, and precipitation or dissolution of calcium carbonate. The estuarine partial pressure of CO2 (pCO2) varied from 530 to 7715 μatm, which represents a strong source of atmospheric CO2. The mean annual air-sea CO2 flux estimated from three different parameterized equations was approximately (25.63 ± 10.25) mol/m2/yr. Furthermore, the annual emission to the atmosphere was approximately (0.031 ± 0.012) Tg C, which accounts for a mere 0.0077%-0.015% of global estuarine emissions. Dissolved inorganic carbon (DIC), total alkalinity (TA) and the pCO2 exhibited high variability throughout the tidal cycle across all cruises. Specifically, the disparities observed between DIC and TA during low and high tides at identical stations during all cruises ranged from approximately 15% to 30%. The variance in the pCO2 was even more pronounced, ranging from approximately 30% to 40%. Thus, tidal discrepancies may need to be taken into consideration to estimate the CO2 flux from estuarine systems more accurately.
Figure 1. Map of Jiulong River estuary with the location of the sampling stations. Different symbols represent different cruises, and the dotted lines are the boundaries of the upper ,middle, and lower reaches of the estuary. The sampling stations J4, J8, J10, J12, J14 were consistently surveyed across the seven cruises in this study.
Figure 2. The variations of salinity, temperature, DO% and turbidity with the longitude
Figure 3. The monthly average water discharge of the Jurong River in 2019 and 2021. The shaded area shows the historical monthly average data from 1961 to 2022 and the four-pointed stars represent the dates of the survey cruises in this study.
Figure 4. Spatial distribution of carbonate system parameters during tidal cycle.
Figure 5. Variations of DIC (a, b, c, d), TA (e, f, g, h) with salinity. grey line is the mixing line obtained by end- member model calculation for each cruise.
Figure 6. Diagrams of the concentrations of DIC and dissolved carbon dioxide ([CO2]) versus salinity during estuarine mixing. (a) represents the calculation of the DIC composition of the estuary, with salinity on the X-axis and DIC concentration on the Y-axis; (b) represents the calculation of [CO2] composition of the estuary, with salinity on the X-axis and dissolved CO2 concentration on the Y-axis.
Figure 7. Histogram of the proportion of DIC composition in the JRE.
Figure 8. Variation of NpCO2(T=24.9℃) with longitude in the JRE
Figure 9. Histogram of the proportion of [CO2] composition in the estuary.
Figure 10. Variations of [CO2] with salinity, the grey dashed line represents the [CO2] from the conservative mixing of the river with the ocean, and the black solid line represents the [CO2] provided by the ocean in the mixing.
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