Blue carbon in human-dominated estuarine and shallow coastal systems

Kuwae, Tomohiro; Kanda, Jun; Kubo, Atsushi; Nakajima, Fumiyuki; Ogawa, Hiroshi; Sohma, Akio; Suzumura, Masahiro

doi:10.1007/s13280-015-0725-x

Cited by 52 publications

(29 citation statements)

References 68 publications

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“…As the majority of CO 2 measurements used to quantify air-sea flux on the NWES are taken outside of these coastal and estuarine areas, observation-based estimates of shelf-wide CO 2 uptake are likely to be overestimated. The complex tapestry of habitats makes coastal carbon fluxes difficult to model and we suggest that more observations of air-sea CO 2 flux in near-shore waters are needed to quantify the size and variability of this flux (Kuwae et al, 2016) and thus better constrain the shelf-wide air-sea CO 2 flux.…”

Section: Atmospheric Co 2 Uptakementioning

confidence: 99%

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

et al. 2020

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A carbon budget for the northwest European continental shelf seas (NWES) was synthesized using available estimates for coastal, pelagic and benthic carbon stocks and flows. Key uncertainties were identified and the effect of future impacts on the carbon budget were assessed. The water of the shelf seas contains between 210 and 230 Tmol of carbon and absorbs between 1.3 and 3.3 Tmol from the atmosphere annually. Offshelf transport and burial in the sediments account for 60-100 and 0-40% of carbon outputs from the NWES, respectively. Both of these fluxes remain poorly constrained by observations and resolving their magnitudes and relative importance is a key research priority. Pelagic and benthic carbon stocks are dominated by inorganic carbon. Shelf sediments contain the largest stock of carbon, with between 520 and 1600 Tmol stored in the top 0.1 m of the sea bed. Coastal habitats such as salt marshes and mud flats contain large amounts of carbon per unit area but their total carbon stocks are small compared to pelagic and benthic stocks due to their smaller spatial extent. The large pelagic stock of carbon will continue to increase due to the rising concentration of atmospheric CO 2 , with associated pH decrease. Pelagic carbon stocks and flows are also likely to be significantly affected by increasing acidity and temperature, and circulation changes but the net impact is uncertain. Benthic carbon stocks will be affected by increasing temperature and acidity, and decreasing oxygen concentrations, although the net impact of these interrelated changes on carbon stocks is uncertain and a major knowledge gap. The impact of bottom trawling on benthic carbon stocks Frontiers in Marine Science | www.frontiersin.org 1 March 2020 | Volume 7 | Article 143Legge et al.Carbon on the Northwest European Shelf is unique amongst the impacts we consider in that it is widespread and also directly manageable, although its net effect on the carbon budget is uncertain. Coastal habitats are vulnerable to sea level rise and are strongly impacted by management decisions. Local, national and regional actions have the potential to protect or enhance carbon storage, but ultimately global governance, via controls on emissions, has the greatest potential to influence the long-term fate of carbon stocks in the northwestern European continental shelf.

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Section: Atmospheric Co 2 Uptakementioning

confidence: 99%

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

et al. 2020

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“…Most of the estuaries studied were strongly heterotrophic. However, some recent estimates showed less heterotrophy or even autotrophy in the estuaries and lower air-water CO 2 fluxes [Crosswell et al, 2012;Maher and Eyre, 2012;Kuwae et al, 2016], which were expected to show high effluxes based on the spatially explicit global typology approach of Laruelle et al [2010]. The large variability between and within estuarine systems make it essential to improve knowledge of estuarine air-water CO 2 fluxes in order to produce better estimates of global estuarine CO 2 exchange [Evans et al, 2013].…”

Section: Introductionmentioning

confidence: 99%

A comparison of CO₂ dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary

Akhand

Chanda

Manna

et al. 2016

Geophysical Research Letters

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The fugacity of CO2 (fCO2 (water)) and air‐water CO2 flux were compared between a river‐dominated anthropogenically disturbed open estuary, the Hugli, and a comparatively pristine mangrove‐dominated semiclosed marine estuary, the Matla, on the east coast of India. Annual mean salinity of the Hugli Estuary (≈7.1) was much less compared to the Matla Estuary (≈20.0). All the stations of the Hugli Estuary were highly supersaturated with CO2 (annual mean ~ 2200 µatm), whereas the Matla was marginally oversaturated (annual mean ~ 530 µatm). During the postmonsoon season, the outer station of the Matla Estuary was under saturated with respect to CO2 and acted as a sink. The annual mean CO2 emission from the Hugli Estuary (32.4 mol C m−2 yr−1) was 14 times higher than the Matla Estuary (2.3 mol C m−2 yr−1). CO2 efflux rate from the Hugli Estuary has increased drastically in the last decade, which is attributed to increased runoff from the river‐dominated estuary.

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“…However, current estimates of the coastal CO 2 budget are based on observations in only limited types of marine systems, irrespective of the large heterogeneity in such biogeochemical settings. In fact, Kuwae et al 4. have recently discussed the possibility of net carbon fixation in certain types of coastal systems including those affected by intense anthropogenic activities.…”

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A significant net sink for CO2 in Tokyo Bay

Kubo

Maeda

Kanda

2017

Sci Rep

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Most estuaries and inland waters are significant source for atmospheric CO2 because of input of terrestrial inorganic carbon and mineralization of terrestrially supplied organic carbon. In contrast to most coastal waters, some estuaries with small freshwater discharge are weak source or sometimes sink for CO2. Extensive surveys of pCO2 in Tokyo Bay showed that the overall bay acts as a strong net sink for atmospheric CO2. Although small area was a consistent source for CO2, active photosynthesis driven by nutrient loading from the land overwhelmed the CO2 budget in the bay. Here we show a comprehensive scheme with a border where air-sea CO2 flux was ±0 between nearshore waters emitting CO2 and offshore waters absorbing CO2. The border in Tokyo Bay was extremely shifted toward the land-side. The shift is characteristic of highly urbanized coastal waters with an extensive sewage treatment system in the catchment area. Because highly urbanized coastal areas worldwide are expected to quadruple by 2050, coastal waters such as Tokyo Bay are expected to increase as well. Through extrapolation of Tokyo Bay data, CO2 emission from global estuaries would be expected to decrease roughly from the current 0.074 PgC year−1 to 0.014 PgC year−1 in 2050.

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Blue carbon in human-dominated estuarine and shallow coastal systems

Cited by 52 publications

References 68 publications

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

A comparison of CO₂ dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary

A significant net sink for CO2 in Tokyo Bay

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Blue carbon in human-dominated estuarine and shallow coastal systems

Cited by 52 publications

References 68 publications

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

Carbon on the Northwest European Shelf: Contemporary Budget and Future Influences

A comparison of CO2 dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary

A significant net sink for CO2 in Tokyo Bay

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Product

Resources

About

A comparison of CO₂ dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary