Journal article
Quantifying tidally-driven CO2 air-sea exchange in a Danish coastal lagoon
Regional studies in marine science, Vol.97, pp.1-9
05/2026
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Abstract
Coastal waters may be a source or sink of carbon dioxide to the atmosphere. Little is known about short-term CO2 dynamics within coastal lagoons often characterised by high anthropogenic nutrient loads and long water residence times. This study presents high-resolution timeseries observations of dissolved CO2 and the groundwater tracer 222Rn every 10 min in Nissum Fjord in Denmark over four days. The hydrology of this coastal lagoon is anthropogenically controlled by tidal gate opening/closing cycles. Ocean inflows enhanced CO2 by 50% to 423 ± 28 µatm compared to 271 ± 71 µatm when the eutrophic lagoon was draining to the ocean. Mixing between high CO2 seawater and low CO2 lagoon waters explained much of the CO2 temporal trends. Negative correlations between p CO2 and both dissolved oxygen and 222Rn imply an indirect effect of groundwater discharge on p CO2 via primary production enhancement. The lower p CO2 within the lagoon was likely related to enhanced nutrient inputs from rivers and groundwater sources sustaining high primary production that release oxygen while removing CO2. Dissolved oxygen imply that primary production was a sink for CO2 inside the lagoon. Low CO2 suggest autotrophy, while persistent O2 undersaturation imply net heterotrophy within the lagoon. On average, Nissum Fjord was a net CO2 sink with an average flux of −41 mmol m² d−1. Variability in CO2 gas water-air exchange is primarily governed by mixing during human-controlled flood gate operations and the direction of flow in and out of the lagoon.
Details
- Title
- Quantifying tidally-driven CO2 air-sea exchange in a Danish coastal lagoon
- Creators
- Janine Steffens - University of GothenburgLinnea Henriksson - University of GothenburgIsaac R. Santos - University of Gothenburg
- Publication Details
- Regional studies in marine science, Vol.97, pp.1-9
- Publisher
- Elsevier BV; AMSTERDAM
- Grant note
- Funding was provided by the Knut and Alice Wallenberg Foundation.
- Identifiers
- 991013370857302368
- Copyright
- © 2026 The Author(s).
- Academic Unit
- National Marine Science Centre; National Centre for Naturopathic Medicine
- Language
- English
- Resource Type
- Journal article