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Optimised water budget of the Gulf of Bothnia (Baltic Sea)
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, Department of Management and Engineering, Industrial Marketing and Industrial Economics. Linköping University, The Institute of Technology.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
2008 (English)Manuscript (preprint) (Other academic)
Abstract [en]

A time-dependent water budget of the Gulf of Bothnia, based on inverse modelling with salinity as a conservative tracer, was developed to estimate monthly water flows for the period 1990-2000. When dealing with time-dependent inverse salinity models, such difficulties as non-physical water flows (too high flows or lack of non-negative flows) between adjacent basins are often encountered. Therefore, different model structures and solution methods were initially tested and evaluated on an array of generated data. The elaboration of the Gulf of Bothnia model was then based on the outcome of these tests. The results showed that the optimisation technique is capable of overcoming the above mentioned difficulties.

Place, publisher, year, edition, pages
2008. Vol. 73, no 3-4, 263-283 p.
Keyword [en]
Budget, water fluxes, optimisation, Gulf of Bothnia, Baltic Sea
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-70070OAI: oai:DiVA.org:liu-70070DiVA: diva2:435235
Available from: 2011-08-17 Created: 2011-08-17 Last updated: 2011-08-17Bibliographically approved
In thesis
1. Silicon cycling in the Baltic Sea: Trends and budget of dissolved silica
Open this publication in new window or tab >>Silicon cycling in the Baltic Sea: Trends and budget of dissolved silica
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Kisels kretslopp i Östersjön : Trender och budget av löst kisel
Abstract [en]

The dissolved silicon (DSi) has a crucial role for growth of a large group of primary producers – diatoms and, hence, impact on functioning of the aquatic food web. This thesis contributes to an increased understanding of the modifications of the DSi cycling in the Baltic Sea. The results provide new information about spatial and temporal changes in DSi concentrations and nutrient ratios for the period 1970-2001 as well as during the 20th century.

For the period 1970-2001, the declining DSi trends were found at the majority of monitoring stations all over the Baltic Sea. This decrease is assumed to be mainly due to the ongoing eutrophication. It is supported by the increasing trends of inorganic nitrogen and phosphorus. The trends have implications for the nutrient ratios, DSi:DIN and DSi:DIP, which are important indicators of the state of an ecosystem. The long-term retrospective DSi budget has shown that the DSi concentrations before major hydrological alterations and eutrophication were about twice the present ones. This decrease is related to both eutrophication and anthropogenic perturbations in the catchment.

The occurrence of DSi concentrations close to the potentially limiting levels has been also analysed. While DSi concentrations are still high in the northern regions of the Baltic, other areas may be at risk of developing Si limitation if the decrease in DSi concentrations persists. The results depict the Baltic Sea journey from being water body with DSi levels sufficient to support diatom production to one that may experience Si limitation and its adverse ecological consequences.

Abstract [sv]

Löst kisel (DSi) har en viktig roll för tillväxten av en stor grupp av primärproducenter – kiselalger, och därmed även påverkar hela den akvatiska näringskedjan. Denna avhandling bidrar till en ökad förståelse av förändringarna i DSi kretsloppet i Östersjön. Resultaten tillhandahåller ny information om rumsliga och tidsmässiga förändringar i DSi koncentrationer såväl för perioden 1970-2001 som för hela 1900-talet.

För perioden 1970-2001 återfanns minskade DSi koncentrationer på mätstationer över hela Östersjön. Minskningen antas främst bero på den pågående övergödningen. Detta antagande stöds av stigande halter av oorganiskt kväve och fosfor. Sammantaget har dessa trender en inverkan på ekosystemets tillstånd och näringsämnenas kvoter, DSi: DIN och DSi: DIP. Ur ett längre tidsperspektiv kan man se att innan övergödningen och de stora hydrologiska ombildningar i Östersjöområdet var DSi koncentrationerna ungefär dubbelt så höga som idag.

Dagens förekomst av DSi koncentrationer som ligger nära de potentiellt begränsande nivåerna har också analyserats. DSi koncentrationerna är fortfarande höga i norra delar av Östersjön, men är i andra områden i riskzonen för att utveckla Si begränsning om minskningen av DSi koncentrationer fortsätter. Resultaten skildrar Östersjöns resa från att vara ett havsområde med DSi halter som är tillräckliga för att understödja kiselalgernas produktion till ett sådant som kan uppleva Si begränsning och dess negativa ekologiska konsekvenser.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 61 + papers 1-5 p.
Series
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 535
Keyword
Dissolved silica, trends, nutrient, nutrient ratios, diatoms, Redfield, limitation, eutrophication, riverine load, budget, fluxes, accumulation, retention, optimisation, Baltic Sea, Löst kisel, trender, näringsämne, näringsämnens kvoter, kiselalger, Redfield, tillväxtbegränsning, övergödning, flodtillförsel, budget, flöden, ackumulering, retention, optimering, Östersjön
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-70071 (URN)978-91-7393-112-0 (ISBN)
Public defence
2011-11-24, TEMCAS, Hus T, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-08-17 Created: 2011-08-17 Last updated: 2014-10-08Bibliographically approved

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Papush, LianaHenningsson, MarkusRahm, LarsDanielsson, Åsa

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