Modelling organic matter dynamics in aquatic systems
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Organic matter is a small but active part of the global carbon cycle. About one third is stored in the oceans where it has a relatively short residence time. The rest is found in the terrestrial biomass and in the soil. Aquatic systems exchange C02 with the atmosphere. Autotrophic organisms fix C02 into their biomass, while heterotrophic organisms respire C02 when utilising organic matter. Systems with large supply of organic matter by inflow can be net heterotrophic, which thus release more C02 than what they fix.
Two systems are studied, the Lake Ortrasket in northern Sweden and the Baltic Sea. In the Baltic primary production is the main source of organic matter, while in the lake dissolved organic matter from inflow dominates. Other characteristics of the Baltic Sea are that it is brackish and has a long residence time compared to the freshwater lake. These systems are studied with different types of models.
For the Baltic proper deep water, an inverse model of the water, salt and heat fluxes was used to estimate an oxygen budget including oxygen consumption. The oxygen levels in the Baltic proper deep water are critical due to the low supply and large consumption. The oxygen consumption is mainly due to organic matter degradation. The low oxygen and salinity levels in the Baltic have consequences for, among other things, the cod spawning success.
The lake model is a mechanistic model of dissolved organic carbon based on a Lagrangian fluid particle model and a one-dimensional physical model. The results show that Lake Ortrasket is a net heterotrophic system. In spite of the differences between the systems, both seems to have similar organic matter degradation rates, ~50 g C m-2 yr-1.
To supplement, time series of phosphate concentration were studied in the Baltic proper surface layer. These show seasonal variations coupled to the primary production, and this time dependence was modelled. The main purpose of the model is to complete corrupt observation time series, which is useful for environmental model studies.
Place, publisher, year, edition, pages
Motala: Kanaltryckeriet , 2000. , 77 p.
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 214
Vatten, Kol, Oceanografi, Hydrologi
Social Sciences Interdisciplinary
IdentifiersURN: urn:nbn:se:liu:diva-32133Local ID: 17993ISBN: 91-7219-825-7OAI: oai:DiVA.org:liu-32133DiVA: diva2:252955
2000-09-22, Hörsal Planck, Fysikhuset, Universitetsområdet Valla, Linköping, 10:00 (Swedish)
Rahm, Lars, Professor
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