Remineralization rate of terrestrial DOC as inferred from CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; supersaturated coastal waters

Fransner, Filippa; Fransson, Agneta; Humborg, Christoph; Gustafsson, Erik; Tedesco, Letizia; Hordoir, Robinson; Nycander, Jonas

doi:10.5194/bg-16-863-2019

Cited by 11 publications

(8 citation statements)

References 51 publications

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“…At mid‐ and high latitudes, estimates of shelf sea tDOC remineralization are typically lower than our estimate for the Sunda Shelf: 40% tDOC remineralization was reported for the Louisiana Shelf (Fichot & Benner, 2014), and 50%–56% on the Eurasian Shelf of the Arctic Ocean (Kaiser et al., 2017; Letscher et al., 2011), although Fransner et al. (2018) inferred that 80% of tDOC entering the Gulf of Bothnia might be labile over a timescale of 1 year. Based on experimental data from 10 of the world's major rivers, Aarnos et al.…”

Section: Discussioncontrasting

confidence: 66%

Extensive Remineralization of Peatland‐Derived Dissolved Organic Carbon and Ocean Acidification in the Sunda Shelf Sea, Southeast Asia

et al. 2021

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Southeast Asia harbors the largest area of the world's tropical peatlands, which are widely distributed in coastal areas of Sumatra and Borneo and store around 69 Pg C of terrestrial organic carbon (Dommain et al., 2014;Page et al., 2011). Consequently, Southeast Asia is also a hotspot of terrestrial organic carbon export to the ocean: the fluvial flux of terrigenous dissolved organic carbon (tDOC) to the Sunda Shelf Sea is ∼21 Tg C yr −1 , which accounts for ∼10% of the annual global land-to-ocean tDOC flux by the world's rivers (Baum et al., 2007;Moore et al., 2011). In addition, most of this peatland area has been anthropogenically disturbed by deforestation and land conversion (Miettinen et al., 2016), which is thought to have increased the peatland tDOC export to the ocean by 32% over the past three decades (Moore et al., 2013;Yupi

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Section: Discussioncontrasting

confidence: 66%

Extensive Remineralization of Peatland‐Derived Dissolved Organic Carbon and Ocean Acidification in the Sunda Shelf Sea, Southeast Asia

et al. 2021

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“…The sea-air CO 2 exchange of 75-274 mmol m −2 d −1 or 0.9-3.3 g C m −2 d −1 also indicates extreme outgassing during the end of the heat wave and can be compared with recent model studies indicating outgassing of up to 60 g C m −2 yr −1 in the nearshore areas of the northern Baltic Sea (Fransner et al, 2019). It is of course difficult to compare simulated annual rates with our measurements that were taken over a few days but it is, nevertheless, striking that the daily sea-air exchange rates of CO 2 presented here are one order of magnitude higher than the simulated ones.…”

Section: Discussionmentioning

confidence: 69%

“…In the Baltic Sea both CO 2 and CH 4 concentrations span an order of magnitude and the highest concentrations reported are >2500 µatm of CO 2 (Fransner et al, 2019) and >1200 nM of CH 4 (Jakobs et al, 2014).…”

Section: Continuous Co 2 and Ch 4 Measurements In Surface Water And Amentioning

confidence: 99%

High Emissions of Carbon Dioxide and Methane From the Coastal Baltic Sea at the End of a Summer Heat Wave

et al. 2019

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The summer heat wave in 2018 led to the highest recorded water temperatures since 1926 -up to 21 • C -in bottom coastal waters of the Baltic Sea, with implications for the respiration patterns in these shallow coastal systems. We applied cavity ringdown spectrometer measurements to continuously monitor carbon dioxide (CO 2 ) and methane (CH 4 ) surface-water concentrations, covering the coastal archipelagos of Sweden and Finland and the open and deeper parts of the Northern Baltic Proper. This allowed us to (i) follow an upwelling event near the Swedish coast leading to elevated CO 2 and moderate CH 4 outgassing, and (ii) to estimate CH 4 sources and fluxes along the coast by investigating water column inventories and air-sea fluxes during a storm and an associated downwelling event. At the end of the heat wave, before the storm event, we found elevated CO 2 (1583 µatm) and CH 4 (70 nmol/L) concentrations. During the storm, a massive CO 2 sea-air flux of up to 274 mmol m −2 d −1 was observed. While water-column CO 2 concentrations were depleted during several hours of the storm, CH 4 concentrations remained elevated. Overall, we found a positive relationship between CO 2 and CH 4 wind-driven sea-air fluxes, however, the highest CH 4 fluxes were observed at low winds whereas highest CO 2 fluxes were during peak winds, suggesting different sources and processes controlling their fluxes besides wind. We applied a box-model approach to estimate the CH 4 supply needed to sustain these elevated CH 4 concentrations and the results suggest a large source flux of CH 4 to the water column of 2.5 mmol m −2 d −1 . These results are qualitatively supported by acoustic observations of vigorous and widespread outgassing from the sediments, with flares that could be traced throughout the water column penetrating the pycnocline and reaching the sea surface. The results suggest that the heat wave triggered CO 2 and CH 4 fluxes in the coastal zones that are comparable with maximum emission rates found in other hot spots, such as boreal and arctic lakes and wetlands. Further, the results suggest that heat waves are as important for CO 2 and CH 4 sea-air fluxes as the ice break up in spring.

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“…Some evidence for this was derived from mesocosm experiments in which bacterial communities from the Northern Bothnian Sea seemed to be better adapted to utilize river-born terrestrial DOC (tDOC) (Herlemann et al, 2017), and where DOM degradation differed between different communities (Logue et al 2016). This is consistent with substantial remineralization rates of tDOC and CO2 supersaturation measured for this area (Fransner et al, 2019). Overall, freshwater bacteria can successfully migrate into the brackish Baltic Sea, where they might gain a selective advantage when riverine DOC is the main carbon source (Kisand et al, 2005;Riemann et al, 2008).…”

Section: Pelagic Microbial Communities Within the Salinity Gradientmentioning

confidence: 63%

“…Carbon is entering the Baltic Sea mainly as total inorganic (TIC) and organic (TOC) C. According to Kuliński and Pempkowiak (2011), riverine C input amounts to 10.9 Tg C yr −1 of which 37.5 % has been estimated as TOC. Most terrestrial derived TOC is respired in the Baltic Sea (Fransner et al, 2016(Fransner et al, , 2019 and therefore exerts positive feedback to atmospheric CO2 concentrations. In contrast, dissolved inorganic carbon (DIC) and alkalinity production via silicate and carbonate weathering constitute a CO2 sink, because atmospheric CO2 is consumed during the various weathering reactions between minerals and https://doi.org/10.5194/esd-2021-33 Preprint.…”

Section: Weathering and Trends In Alkalinity And Tocmentioning

confidence: 99%

Baltic Earth Assessment Report on the biogeochemistry of the Baltic Sea

Kuliński

Rehder

Asmala

et al. 2021

Preprint

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Abstract. Location, specific topography and hydrographic setting together with climate change and strong anthropogenic pressure are the main factors shaping the biogeochemical functioning and thus also the ecological status of the Baltic Sea. The recent decades have brought significant changes in the Baltic Sea. First, the rising nutrient loads from land in the second half of the 20th century led to eutrophication and spreading of hypoxic and anoxic areas, for which permanent stratification of the water column and limited ventilation of deep water layers made favourable conditions. Since the 1980s the nutrient loads to the Baltic Sea have been continuously decreasing. This, however, has so far not resulted in significant improvements in oxygen availability in the deep regions, which has revealed a slow response time of the system to the reduction of the land-derived nutrient loads. Responsible for that is the low burial efficiency of phosphorus at anoxic conditions and its remobilization from sediments when conditions change from oxic to anoxic. This results in a stoichiometric excess of phosphorus available for organic matter production, which promotes the growth of N2-fixing cyanobacteria and in turn supports eutrophication. This assessment reviews the available and published knowledge on the biogeochemical functioning of the Baltic Sea. In its content, the paper covers the aspects related to changes in carbon, nitrogen and phosphorus (C, N and P) external loads, their transformations in the coastal zone, changes in organic matter production (eutrophication) and remineralization (oxygen availability), and the role of sediments in burial and turnover of C, N and P. In addition to that, this paper focuses also on changes in the marine CO2 system, structure and functioning of the microbial community and the role of contaminants for biogeochemical processes. This comprehensive assessment allowed also for identifying knowledge gaps and future research needs in the field of marine biogeochemistry in the Baltic Sea.

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Remineralization rate of terrestrial DOC as inferred from CO<sub>2</sub> supersaturated coastal waters

Cited by 11 publications

References 51 publications

Extensive Remineralization of Peatland‐Derived Dissolved Organic Carbon and Ocean Acidification in the Sunda Shelf Sea, Southeast Asia

Extensive Remineralization of Peatland‐Derived Dissolved Organic Carbon and Ocean Acidification in the Sunda Shelf Sea, Southeast Asia

High Emissions of Carbon Dioxide and Methane From the Coastal Baltic Sea at the End of a Summer Heat Wave

Baltic Earth Assessment Report on the biogeochemistry of the Baltic Sea

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