Tackling Hypoxia in the Baltic Sea: Is Engineering a Solution?

Conley, Daniel J.; Bonsdorff, Erik; Carstensen, Jacob; Destouni, Georgia; Gustafsson, Bo; Hansson, Lars‐Anders; Rabalais, Nancy N.; Voß, Maren; Zillén, Lovisa

doi:10.1021/es8027633

Cited by 105 publications

(87 citation statements)

References 21 publications

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“…The oxic area we calculated by using the 100 m depth line is ∼389 000 km 2 which is very close to the oxic area calculated from the DYNAS project for approach 1 (∼392 000 km 2 ). In the Central Baltic and the Gulf of Finland, usually permanent anoxic conditions prevail with the appearance of H 2 S below water-depths >100 m whereas in waters above 100 m depth anoxia occurs temporarily (Conley et al, 2009b). Furthermore, our calculated area shows good agreement with the anoxic areas presented in Hansson et al, 2009, and with the map showing the Baltic Sea anoxic areas of 2008 presented on the website of the Baltic Sea Portal (www.fimr.fi).…”

Section: Uncertaintiessupporting

confidence: 87%

“…Changes only occur during the non-periodic salt water intrusions from the North Sea during which oxygenated high-density salt-water fills the Baltic Sea basins successively thus terminating stagnation of bottom waters (Conley et al, 2002). The depth of the oxycline is variable and during periods of stagnation located at around 100 m depth in the central Gotland basin (Conley et al, 2009b;Baltic Environmental Database). A rise of the oxycline to a depth of 80 m has been well documented in the past (Baltic Environmental Database).…”

Section: Resulting Inmentioning

confidence: 99%

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Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

et al. 2010

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Abstract.Rates of denitrification in sediments were measured with the isotope pairing technique at different sites in the southern and central Baltic Sea. The rates varied between 0.5 µmol N m −2 h −1 in sands and 28.7 µmol N m −2 h −1 in muddy sediments and showed a good correlation to the organic carbon contents of the surface sediments. N-removal rates via sedimentary denitrification were estimated for the entire Baltic Sea calculating sediment specific denitrification rates and interpolating them to the whole Baltic Sea area. Another approach was carried out by using the relationship between the organic carbon content and the rate of denitrification. The N-removal by denitrification in sediments varied between 426-652 kt N a −1 , which is around 48-73% of the external N inputs delivered via rivers, coastal point sources, and atmospheric deposition. Moreover, an expansion of the anoxic bottom areas was considered under the assumption of a rising oxycline from 100 to 80 m water depth. This leads to an increase of the area with anoxic conditions and an overall decrease in sedimentary denitrification by 14%. Overall, we show here that this type of data extrapolation is a powerful tool to estimate the nitrogen losses for a whole coastal sea and may be applicable to other coastal regions and enclosed seas.

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Section: Uncertaintiessupporting

confidence: 87%

Section: Resulting Inmentioning

confidence: 99%

Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

et al. 2010

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“…Since the 1970s, the Baltic Sea has been subject to strong anthropogenic pressures (Conley et al, 2009) leading to eelgrass declines in several countries . In the 1930s, the Danish eelgrass meadows were significantly reduced by the wasting disease (Rasmussen, 1977).…”

Section: Consequences Of Seagrass Loss For Carbon Poolsmentioning

confidence: 99%

Blue carbon stocks in Baltic Sea eelgrass (<i>Zostera marina</i>) meadows

et al. 2016

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Abstract. Although seagrasses cover only a minor fraction of the ocean seafloor, their carbon sink capacity accounts for nearly one-fifth of the total oceanic carbon burial and thus play a critical structural and functional role in many coastal ecosystems. We sampled 10 eelgrass (Zostera marina) meadows in Finland and 10 in Denmark to explore seagrass carbon stocks (C org stock) and carbon accumulation rates (C org accumulation) in the Baltic Sea area. The study sites represent a gradient from sheltered to exposed locations in both regions to reflect expected minimum and maximum stocks and accumulation. The C org stock integrated over the top 25 cm of the sediment averaged 627 g C m −2 in Finland, while in Denmark the average C org stock was over 6 times higher (4324 g C m −2 ). A conservative estimate of the total organic carbon pool in the regions ranged between 6.98 and 44.9 t C ha −1 . Our results suggest that the Finnish eelgrass meadows are minor carbon sinks compared to the Danish meadows, and that majority of the C org produced in the Finnish meadows is exported. Our analysis further showed that > 40 % of the variation in the C org stocks was explained by sediment characteristics, i.e. dry density, porosity and silt content. In addition, our analysis show that the root : shoot ratio of Z. marina explained > 12 % and the contribution of Z. marina detritus to the sediment surface C org pool explained > 10 % of the variation in the C org stocks. The mean monetary value for the present carbon storage and carbon sink capacity of eelgrass meadows in Finland and Denmark, were 281 and 1809 EUR ha −1 , respectively. For a more comprehensive picture of seagrass carbon storage capacity, we conclude that future blue carbon studies should, in a more integrative way, investigate the interactions between sediment biogeochemistry, seascape structure, plant species architecture and the hydrodynamic regime.

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“…8 differ in their capability to sustain eutrophication and hypoxia. Especially with regards to the planning of hypoxia remediation strategies (Conley et al, 2009b), knowledge of the expected response of the system to changes in total hypoxic area is crucial. The enhanced C org burial observed along the deep basin margins during intervals of maximum hypoxic area (Figs.…”

Section: Wider Implications For P-driven Eutrophication/ Hypoxia Feedmentioning

confidence: 99%

Beyond the Fe-P-redox connection: preferential regeneration of phosphorus from organic matter as a key control on Baltic Sea nutrient cycles

et al. 2011

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Abstract. Patterns of regeneration and burial of phosphorus (P) in the Baltic Sea are strongly dependent on redox conditions. Redox varies spatially along water depth gradients and temporally in response to the seasonal cycle and multidecadal hydrographic variability. Alongside the welldocumented link between iron oxyhydroxide dissolution and release of P from Baltic Sea sediments, we show that preferential remineralization of P with respect to carbon (C) and nitrogen (N) during degradation of organic matter plays a key role in determining the surplus of bioavailable P in the water column. Preferential remineralization of P takes place both in the water column and upper sediments and its rate is shown to be redox-dependent, increasing as reducing conditions become more severe at greater water-depth in the deep basins. Existing Redfield-based biogeochemical models of the Baltic may therefore underestimate the imbalance between N and P availability for primary production, and hence the vulnerability of the Baltic to sustained eutrophication via the fixation of atmospheric N. However, burial of organic P is also shown to increase during multidecadal intervals of expanded hypoxia, due to higher net burial rates of organic matter around the margins of the deep basins. Such intervals may be characterized by basin-scale acceleration of all fluxes within the P cycle, including productivity, regeneration and burial, sustained by the relative accessibility of the water column P pool beneath a shallow halocline.

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Tackling Hypoxia in the Baltic Sea: Is Engineering a Solution?

Cited by 105 publications

References 21 publications

Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

Blue carbon stocks in Baltic Sea eelgrass (<i>Zostera marina</i>) meadows

Beyond the Fe-P-redox connection: preferential regeneration of phosphorus from organic matter as a key control on Baltic Sea nutrient cycles

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Tackling Hypoxia in the Baltic Sea: Is Engineering a Solution?

Cited by 105 publications

References 21 publications

Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

Blue carbon stocks in Baltic Sea eelgrass (&lt;i&gt;Zostera marina&lt;/i&gt;) meadows

Beyond the Fe-P-redox connection: preferential regeneration of phosphorus from organic matter as a key control on Baltic Sea nutrient cycles

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Blue carbon stocks in Baltic Sea eelgrass (<i>Zostera marina</i>) meadows