Carbon monoxide cycling in the Ria Formosa Lagoon (southern Portugal) during summer 2021
Abstract. Carbon monoxide (CO) is an atmospheric trace gas that plays a crucial role in the oxidizing capacity of the Earth’s atmosphere. Moreover, it functions as an indirect greenhouse gas, influencing the lifetimes of potent greenhouse gases such as methane. Albeit being an overall source of atmospheric CO, the role of coastal regions in the marine cycling of CO and how its budget can be affected by anthropogenic activities, remain uncertain. Here, we present the first measurements of dissolved CO in the Ria Formosa Lagoon, an anthropogenically influenced system in southern Portugal. The dissolved CO concentrations in the surface layer ranged from 0.16 to 3.1 nmol L−1 with an average concentration of 0.75 ± 0.57 nmol L−1. The CO saturation ratio ranged from 1.7 to 32.2, indicating that the lagoon acted as a source of CO to the atmosphere in May 2021. The estimated average sea-to-air flux density was 1.53 μmol m−2 d−1, mainly fueled by CO photochemical production. Microbial consumption accounted for 83 % of the CO production, suggesting that the resulting CO emissions to the atmosphere were modulated by microbial consumption in the surface waters of the Ria Formosa Lagoon. The results from an irradiation experiment with aquaculture effluent water indicated that aquaculture facilities in the Ria Formosa Lagoon seem to be a negligible source of atmospheric CO.
Guanlin Li et al.
Status: open (until 11 Jul 2023)
- CC1: 'Comment on egusphere-2023-771', Hong-Hai Zhang, 01 Jun 2023 reply
Guanlin Li et al.
Guanlin Li et al.
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Interactive comment on “Carbon monoxide cycling in the Ria Formosa Lagoon (southern Portugal) during summer 2021” by Guanlin Li et al.
The manuscript by Li et al. deals with a measured of the concentrations of carbon monoxide in the water column in the Ria Formosa Lagoon system and determine the potential impact of aquaculture activities on CO cycling in this region. It addresses an under-investigated topic, clearly of interest for the BG community, of general biogeochemical relevance as well as consequences for the role of coastal ecosystems for the (trans)formation of climate-relevant gases. The authors have very carefully exploited their data and provided the appropriate statistical evaluation to support their results, and extracted the main findings of this study. However, from my point of view, I have some suggestions to render the work more attractive to readers. Therefore, I suggest its publication after minor revisions.
Page 4 Lines 107: The author mentioned in the manuscript that because of a technical problem with the calibration of the CO analyzer, data was corrected by the correction factor. It is not clear for me that the correction factor is for atmospheric samples or for all samples?
Page 9 Lines 263-264: as mentioned in the previous paragraphs ‘with the assumption of a steady state, the sum of the CO sources and sinks is equal to zero’. It should not be mentioned here again in the form of a conclusion. It is recommended to modify or delete.
For the microbial CO consumption experiment, should the influence of dark (thermodynamic) production on CO be considered?
should the sampling density be increased, especially between 0 and 24 hours? And the author mentioned that CO net production rate for Olhão aquaculture effluent is extremely low, microbial CO consumption was counteracting the CO photochemical production almost completely. Would the author consider using some testing methods to analyze the consumption of microorganisms to confirm the experimental results?
For the aquaculture incubation experiments, should the sampling density be increased, especially between 0 and 24 hours? And the author mentioned that CO net production rate for Olhão aquaculture effluent is extremely low, microbial CO consumption was counteracting the CO photochemical production almost completely. Would the author consider using some testing methods to analyze the consumption of microorganisms to confirm the experimental results?
The conclusion should not contain too many references.
Minor comments for the figures:
The quality of the figure should be improved (Fig. 2).
Fig. 5(a), the color for the right vertical axis for CO saturation ratio is oversaturated, I suggest changing to another color.
The legend of Figure 8 is not very clear.