Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

Hylén, Astrid; Velde, Sebastiaan van de; Kononets, Mikhail; Luo, Mingyue; Almroth‐Rosell, Elin; Hall, Per

doi:10.5194/bg-18-2981-2021

Cited by 10 publications

(11 citation statements)

References 62 publications

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“…4). Similar patterns were also seen for other biogenic compounds (DIC, dissolved silicate, dissolved inorganic phosphorus), suggesting that the degradation of organic matter increased temporarily after the inflow and amplified the NH þ 4 release (Hylén et al 2021). Overall, the NH þ 4 effluxes were one order of magnitude higher than the NO À…”

Section: Discussionsupporting

confidence: 58%

“…Fluxes of DIC and dissolved inorganic nitrogen (

{NH}_{4}^{+}

{NO}_{x}^{-}

) at Stas. D–F were presented by Hylén et al (2021). At these deeper stations, fluxes of O 2 were only measurable the year following inflows (2017 at Sta.…”

Section: Resultsmentioning

confidence: 99%

“…As the MBI and following inflows created a second oxic–anoxic interface in the water column, the pelagic N removal is likely to have increased considerably, substantially exceeding the sedimentary N removal (Hall et al 2017). In conclusion, the sediment at the newly oxygenated stations was not sites of efficient removal of fixed N. The natural oxygenation event stimulated production of N 2 O and recycling of fixed N through DNRA, while increased organic matter degradation lead to elevated release of fixed N as

{NH}_{4}^{+}

(Hylén et al 2021). Consequently, the main outcome from this temporary oxygenation was that the sediments continued to contribute to accumulation, rather than removal, of fixed N in the system.…”

Section: Conclusion and Environmental Implicationsmentioning

confidence: 99%

“…It is also possible that % DNRA changed over the year. The sampling for this study was conducted right before the spring bloom each year (Hylén et al 2021). The importance of DNRA could therefore have grown in the months after the samplings, as the spring bloom was deposited on the sediment and increased the supply of reactive organic matter, for example, in the form of aggregates.…”

Section: Strongly Reduced Sediments Favor Dnramentioning

confidence: 99%

“…Sediment-water fluxes were calculated as the change in concentration per unit sediment surface area and time in each chamber following Hylén et al (2021). Fluxes of O 2 were calculated from linear fits of the chamber O 2 concentration over time.…”

Section: Calculations and Statisticsmentioning

confidence: 99%

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Enhanced benthic nitrous oxide and ammonium production after natural oxygenation of long‐term anoxic sediments

Hylén

Bonaglia

Robertson

et al. 2021

Limnology & Oceanography

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Coastal and shelf sediments are central in the global nitrogen (N) cycle as important sites for the removal of fixed N. However, this ecosystem service can be hampered by ongoing deoxygenation in many coastal areas. Natural reoxygenation could reinstate anoxic sediments as sites where fixed N is removed efficiently. To investigate this further, we studied benthic N cycling in previously long-term anoxic sediments, following a large intrusion of oxygenated water to the Baltic Sea. During three campaigns in 2016-2018, we measured in situ sediment-water fluxes of ammonium (NH þ 4 ), nitrate (NO À 3 ), oxygen (O 2 ), dissolved inorganic carbon, and NO À 3 reduction processes using benthic chamber landers. Sediment microprofiles of O 2 , nitrous oxide (N 2 O), and hydrogen sulfide were measured in sediment cores. At a permanently oxic station, denitrification to N 2 was the main NO À 3 reduction process. Benthic N 2 O production appeared to be linked to nitrification, although no net N 2 O fluxes from the sediment were detected. At newly oxygenated sites, dissimilatory NO À 3 reduction to NH þ 4 comprised almost half of the total NO À 3 reduction. At these stations, the removal of fixed N was inefficient due to high effluxes of NH þ 4 . Sedimentary N 2 O production was associated with incomplete denitrification, accounting for 41-88% of the total denitrification rate. Microprofiling revealed algae aggregates as potential hotspots of seafloor N 2 O production. Our results show that transient oxygenation of euxinic systems initiates benthic NO À 3 reduction, but may not lead to efficient sedimentary removal of fixed N. Instead, recycling of N compounds is promoted, which may accelerate the return to anoxia.

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Section: Discussionsupporting

confidence: 58%

“…Fluxes of DIC and dissolved inorganic nitrogen (

{NH}_{4}^{+}

{NO}_{x}^{-}

) at Stas. D–F were presented by Hylén et al (2021). At these deeper stations, fluxes of O 2 were only measurable the year following inflows (2017 at Sta.…”

Section: Resultsmentioning

confidence: 99%

{NH}_{4}^{+}

Section: Conclusion and Environmental Implicationsmentioning

confidence: 99%

Section: Strongly Reduced Sediments Favor Dnramentioning

confidence: 99%

Section: Calculations and Statisticsmentioning

confidence: 99%

See 3 more Smart Citations

Enhanced benthic nitrous oxide and ammonium production after natural oxygenation of long‐term anoxic sediments

Hylén

Bonaglia

Robertson

et al. 2021

Limnology & Oceanography

Self Cite

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Decadal changes in surface CO₂ concentrations and CO₂ fluxes in a mountain lake

Obertegger,

Corradini,

Cerasino

et al. 2024

Limnology & Oceanography

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Climate warming impacts biogeochemical cycles in lakes. However, the factors controlling CO2 dynamics in mountain lakes over multidecadal scales are poorly understood. Here, we capitalized on long‐term monthly data (1995–2022) of oligotrophic mountain Lake Tovel and calculated surface CO2 concentrations and flux by applying geochemical relationships and the thin boundary layer approach. Advanced time‐series and regression modeling was used to determine temporal patterns and environmental parameters explaining surface CO2 concentrations and flux. Surface CO2 concentrations were highest from 2009 to 2017 (annual mean: 109.1 μmol CO2 L−1) but lower before and after this period. Concomitantly, the air–water CO2 flux (μmol CO2 m−2 d−1) showed a period of lowest (mean1995–2010: 6.4 ± 0.7), highest (mean2011–2017: 35.7 ± 2.1), and intermediate emissions (mean2018–2022: 19.3 ± 4.7). Temporal modeling showed that hypolimnetic and deep hypolimnetic dissolved oxygen (DO) had the same change points and trends as surface CO2 concentrations. In multiple linear regression, hypolimnetic DO, silica, and the standardized precipitation index (pseudo‐R2adj. = 0.62; p < 0.01) best predicted annual mean surface CO2 concentrations. Regression results and the overlap between temporal trend patterns indicated that surface CO2 concentrations of Lake Tovel were positively influenced by external (loading of allochthonous carbon) and internal (lake autumn mixing) factors. The recent decline in surface CO2 concentrations from the year 2018 was attributed to increased stratification that offset lake autumn mixing and thus lead to the observed decline. These results help us to better understand the carbon cycle in mountain lakes in a changing climate.

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Warm saltwater inflows strengthen oxygen depletion in the western Baltic Sea

Barghorn,

Meier,

Radtke

et al. 2024

Clim Dyn

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Hypoxia is a major environmental threat for coastal seas, including the strongly-stratified Baltic Sea in northern Europe. There, a pronounced increase in nutrient loads since the 1950s led to the development of one of the largest hypoxic areas worldwide. So far, other drives of hypoxia, like the increase in water temperatures due to global warming, have been considered minor compared to eutrophication. We show, by analyzing 159-years long hindcast simulations of three different Baltic Sea models, that exceptional warming trends in deep water layers of the western Baltic Sea deteriorated the local oxygen conditions. The above-average warming is only to a small extent attributed directly to global warming, but mainly to a shift in the seasonality of saltwater inflows from the North Sea towards more warm summer and early autumn inflows. Hence, we identify a so far unknown driver of oxygen depletion in the western Baltic Sea with potentially serious ecological consequences.

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Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

Cited by 10 publications

References 62 publications

Enhanced benthic nitrous oxide and ammonium production after natural oxygenation of long‐term anoxic sediments

Enhanced benthic nitrous oxide and ammonium production after natural oxygenation of long‐term anoxic sediments

Decadal changes in surface CO₂ concentrations and CO₂ fluxes in a mountain lake

Warm saltwater inflows strengthen oxygen depletion in the western Baltic Sea

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Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

Cited by 10 publications

References 62 publications

Enhanced benthic nitrous oxide and ammonium production after natural oxygenation of long‐term anoxic sediments

Enhanced benthic nitrous oxide and ammonium production after natural oxygenation of long‐term anoxic sediments

Decadal changes in surface CO2 concentrations and CO2 fluxes in a mountain lake

Warm saltwater inflows strengthen oxygen depletion in the western Baltic Sea

Contact Info

Product

Resources

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Decadal changes in surface CO₂ concentrations and CO₂ fluxes in a mountain lake