A New Phosphorus Paradigm for the Baltic Proper

Stigebrandt, Anders; Rahm, Lars; Viktorsson, Lena; Ödalen, Malin; Hall, Per; Liljebladh, Bengt

doi:10.1007/s13280-013-0441-3

Cited by 41 publications

(71 citation statements)

References 36 publications

(56 reference statements)

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“…The low N:P ratios are caused by removal of fixed nitrogen (denitrification and anammox) at both the oxycline/nitracline in water column (Dalsgaard et al, 2013) and in sediments underlying oxygenated or at least nitrate containing bottom water (Tuominen et al, 1998;Deutsch et al, 2010) together with enhanced benthic P regeneration due to oxygen depletion in deep waters (Jilbert et al, 2011;Viktorsson et al, 2013a). The change in the bottom area covered by hypoxic water in the Baltic Sea, but not the external P load, has been found to correlate well with variations in the dissolved water column P pool size (Conley et al, 2002;Stigebrandt et al, 2014). This correlation indirectly indicates the importance of oxygen in regulating the capacity of sediments to release/retain P in the Baltic Sea.…”

Section: Introductionmentioning

confidence: 96%

Influence of Natural Oxygenation of Baltic Proper Deep Water on Benthic Recycling and Removal of Phosphorus, Nitrogen, Silicon and Carbon

et al. 2017

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At the end of 2014, a Major Baltic Inflow (MBI) brought oxygenated, salty water into the Baltic proper and reached the long-term anoxic Eastern Gotland Basin (EGB) by March 2015. In July 2015, we measured benthic fluxes of phosphorus (P), nitrogen (N) and silicon (Si) nutrients and dissolved inorganic carbon (DIC) in situ using an autonomous benthic lander at deep sites (170-210 m) in the EGB, where the bottom water oxygen concentration was 30-45 µM. The same in situ methodology was used to measure benthic fluxes at the same sites in 2008-2010, but then under anoxic conditions. The high efflux of phosphate under anoxic conditions became lower upon oxygenation, and turned into an influx in about 50% of the flux measurements. The C:P and N:P ratios of the benthic solute flux changed from clearly below the Redfield ratio (on average about 70 and 3-4, respectively) under anoxia to approaching or being well above the Redfield ratio upon oxygenation. These observations demonstrate retention of P in newly oxygenated sediments. We found no significant effect of oxygenation on the benthic ammonium, silicate and DIC flux. We also measured benthic denitrification, anammox, and dissimilatory nitrate reduction to ammonium (DNRA) rates at the same sites using isotope-pairing techniques. The bottom water of the long-term anoxic EGB contained less than 0.5 µM nitrate in 2008-2010, but the oxygenation event created bottom water nitrate concentrations of about 10 µM in July 2015 and the benthic flux of nitrate was consistently directed into the sediment. Nitrate reduction to both dinitrogen gas (denitrification) and ammonium (DNRA) was initiated in the newly oxygenated sediments, while anammox activity was negligible. We estimated the influence of this oxygenation event on the magnitudes of the integrated benthic P flux (the internal P load) and the fixed N removal through benthic and pelagic denitrification by comparing with a hypothetical Hall et al.Oxygenation Effect on Benthic Fluxes scenario without the MBI. Our calculations suggest that the oxygenation triggered by the MBI in July 2015, extrapolated to the basin-wide scale of the Baltic proper, decreased the internal P load by 23% and increased the total (benthic plus pelagic) denitrification by 18%.

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Section: Introductionmentioning

confidence: 96%

Influence of Natural Oxygenation of Baltic Proper Deep Water on Benthic Recycling and Removal of Phosphorus, Nitrogen, Silicon and Carbon

et al. 2017

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“…However, the processes controlling the P burial under anoxic conditions are still not fully understood (e.g. Stigebrandt et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Evidence for vivianite formation and its contribution to long-term phosphorus retention in a recent lake sediment: a novel analytical approach

et al. 2014

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Abstract. Vivianite, Fe 3 (PO 4 ) 2 · 8H 2 O, is a ferrous iron phosphate mineral which forms in waterlogged soils and sediments. The phosphorus (P) bound in its crystal lattice is considered to be immobilised because vivianite is stable under anoxic, reducing, sedimentary conditions. Thus, vivianite formation can make a major contribution to P retention during early diagenesis. Much remains unknown about vivianite in sediments, because technical challenges have rendered direct identification and quantification difficult. To identify vivianite and assess its significance for P burial during early diagenesis we studied the consequences of a 1992/1993 in-lake application of FeCl 3 and Fe(OH) 3 aimed at restoring Lake Groß-Glienicke (Berlin, Germany). In a novel approach, we firstly applied a heavy-liquid separation to the iron-rich surface sediments which allowed direct identification of vivianite by X-ray diffraction in the high-density (ρ > 2.3 g cm −3 ) sediment fraction. Secondly, we assessed the contribution of vivianite to P retention, combining results from chemical digestion with magnetic susceptibility data derived from magnetic hysteresis measurements. Scanning electron microscopy revealed that the dark blue spherical vivianite nodules were 40-180 µm in diameter, and formed of platy-and needle-shaped crystal aggregates. Although equilibrium calculations indicated supersaturation of vivianite throughout the upper 30 cm of the sediment, the vivianite deposits were homogeneously distributed within, and restricted to, the upper 23 cm only. Thus, supersaturated pore water alone cannot serve as a reliable predictor for the in situ formation of vivianite. In Lake Groß-Glienicke, vivianite formation continues to be triggered by the artificial iron amendment more than 20 yr ago, significantly contributing to P retention in surface sediments.

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“…Because the pumped water is interleaved in the lower part of the halocline, the dynamics of the surface layer, including the local supply of nutrients and the production of organic mat- ter, should be negligibly influenced by the pumping. However, since the oxygenation reduces the leakage of phosphorus into the deepwater of the Bornholm Basin (Stigebrandt et al, 2014a), this water will carry less phosphorus with it when it is flushed and further transported into the basins east of the Bornholm Basin. Consequently, there will be a decreased upwelling of P in the basins east of the Bornholm Basin.…”

Section: Hydrographical Changes Of Pumping In the Bornholm Basinmentioning

confidence: 99%

“…The Baltic is the largest sea area with anthropogenically related low oxygen concentrations in the world (Diaz and Rosenberg, 2008) because of increased input of organic matter (Bonsdorff et al, 1997) that has changed the ecosystem properties (Elmgren, 1989;Rosenberg et al, 1990). The increased input of organic matter has been boosted by extensive leakage of phosphorus from anoxic bottoms that has increased the phosphorus content in the water column in spite of a halved external supply of phosphorus since the 1980s (Stigebrandt et al, 2014a). As a consequence, the structure and function of the Baltic ecosystem is affected by two main factors -horizontally by increasing…”

Section: Introductionmentioning

confidence: 99%

Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass – a model study

et al. 2015

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Abstract. We develop and use a circulation model to estimate hydrographical and ecological changes in the isolated basin water of the Bornholm Basin. By pumping welloxygenated so-called winter water to the greatest depth, where it is forced to mix with the resident water, the rate of deepwater density reduction increases as well as the frequency of intrusions of new oxygen-rich deepwater. We show that pumping 1000 m 3 s −1 should increase the rates of water exchange and oxygen supply by 2.5 and 3 times, respectively. The CRV (cod reproduction volume), the volume of water in the isolated basin meeting the requirements for successful cod reproduction (S > 11, O 2 > 2 mL L −1 ), should every year be greater than 54 km 3 , which is an immense improvement, since it has been much less in certain years. Anoxic bottoms should no longer occur in the basin, and hypoxic events will become rare. This should permit extensive colonization of fauna on the earlier periodically anoxic bottoms. Increased biomass of benthic fauna should also mean increased food supply to economically valuable demersal fish like cod and flatfish. In addition, re-oxygenation of the sediments should lead to increased phosphorus retention by the sediments.

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A New Phosphorus Paradigm for the Baltic Proper

Cited by 41 publications

References 36 publications

Influence of Natural Oxygenation of Baltic Proper Deep Water on Benthic Recycling and Removal of Phosphorus, Nitrogen, Silicon and Carbon

Influence of Natural Oxygenation of Baltic Proper Deep Water on Benthic Recycling and Removal of Phosphorus, Nitrogen, Silicon and Carbon

Evidence for vivianite formation and its contribution to long-term phosphorus retention in a recent lake sediment: a novel analytical approach

Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass – a model study

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