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- Stigebrandt, Anders, 1942, et al.
(författare)
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A new Phosphorus Paradigm for the Baltic Proper
- 2014
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 43:5, s. 634-643
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Tidskriftsartikel (refereegranskat)abstract
- The external phosphorus (P) loading has been halved, but the P content in the water column and the area of anoxic bottoms in Baltic proper has increased during the last 30 years. This can be explained by a temporary internal source of dissolved inorganic phosphorus (DIP) that is turned on when the water above the bottom sediment becomes anoxic. A load-response model, explaining the evolution from 1980 to 2005, suggests that the average specific DIP flux from anoxic bottoms in the Baltic proper is about 2.3 g P m-2 year-1. This is commensurable with fluxes estimated in situ from anoxic bottoms in the open Baltic proper and from hydrographic data in the deep part of Bornholm Basin. Oxygenation of anoxic bottoms, natural or manmade, may quickly turn off the internal P source from anoxic bottoms. This new P-paradigm should have far-reaching implications for abatement of eutrophication in the Baltic proper.
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| 2. |
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| 3. |
- Stigebrandt, Anders, 1942, et al.
(författare)
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Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass - a model study
- 2015
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Ingår i: Ocean Science. - 1812-0784 .- 1812-0792. ; 11:1, s. 93-110
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Tidskriftsartikel (refereegranskat)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 1000m3 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, O2 > 2mL L-1), should every year be greater than 54 km3, 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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| 4. |
- Ödalen, Malin, 1980, et al.
(författare)
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Factors of potential importance for the location of winddriven water pumps in the Bornholm Basin, BOX-WIN Report no 2
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The project BOX-WIN aims to construct a full-scale wind-driven pump for combined deepwater oxygenation and production of electric power to the grid. The objective of this report is to prospect the Bornholm Basin for suitable locations for the anchoring of winddriven pumps. The investigated features are water depth, sediment type, extreme wind, current, wave and sea ice conditions, proximity to munition dumpsites, warning zones and sea floor installations, distance to land, ship traffic intensity and important areas for birds and for cod reproduction. By initial inspections of topography, six sites that may be of interest for a pump installation in the Bornholm Basin are further assessed. For safety reasons, no locations within the primary dumping zone for chemical munitions have been considered. However, some sites are located within the secondary dumping zone and a military warning zone. At the investigated sites, sediment types range from mud to sand. In areas with sandy sediments, extreme events may cause current speeds of up to 1 m s-1. Maximum wind speed and wave height are estimated to about 45 m s-1 and 15 m respectively. Ice coverage only appears during severe or extremely severe ice winters and primarily in the western parts of the basin. All of the sites are far from sea floor installations such as submarine power cables and the Nord Stream pipeline. Most of the evaluated locations are far from land ( >20 km), but two sites are in the vicinity of the small island Christiansø, north-east of Bornholm island. However, these two sites are located within important bird areas. The entire Bornholm Basin is also a crucial area for cod spawning. Thus, this is an example of an ecological factor that may be of importance, independent of which location is chosen for the anchoring of a wind-driven pump. Ship traffic is more intense in the northern part of the area, due to the presence of the main shipping lane. A minimum in ship traffic is found north-east of Bornholm, near Christiansø. A concluding table presenting the status of the investigated characteristics at each site is constructed to summarize the report.
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| 5. |
- Ödalen, Malin, 1980, et al.
(författare)
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Hydrographical conditions in the Bornholm Basin of importance for oxygenation of the deepwater by pumping down oxygen saturated water from above the halocline
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this report is to present the temperature, salinity and oxygen concentration at different standard depths in the Bornholm Sea. This information is valuable for determination of the depth range of water intakes to water pumps aimed for oxygenation of the Bornholm Basin deepwater. Observations made in the period 1970 – 2010 at the station BY5 located in the Bornholm Sea deep basin were used for the analysis. The results for the long-term mean values show that salinity increases strongly in the halocline, at depths of 50 – 70 m, and that there is a minimum in mean temperature just above the halocline, which is typical for the Baltic proper. The long-term mean oxygen concentration decreases with depth from the maximum 11.3 – 11.4 g O2 m-3 at 0 – 40 m depth to less than 2 g O2 m-3 at 80m. The variability is partitioned into three period bands, which include variations shorter than, equal to and longer than one year respectively. We conclude that for temperature the largest variability occurs in the surface layer, due to the annual cycle. Both oxygen and salinity show the largest variability within the halocline, due to many small inflows from the Kattegat. Below the halocline, inter-annual variations are dominant due to long periods of stagnation when there is no water exchange. For depths below 50 m, there are long-term trends with increasing temperature and decreasing oxygen concentrations. In the depth range 20 – 50 m, annual averages show that higher temperatures have become more common in the late 1980’s and that the vertical salinity gradient has become more pronounced, beginning in the 1990’s. At a depth of 30 m, oxygen levels are at a maximum and the density is low. Temperature is close to the deepwater temperature and shows relatively low annual variability
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