| 1. |
|
|
| 2. |
- Johansson, Torbjörn
(författare)
-
Phosphorus Emissions from Fish Farms : Observed and Predicted Effects
- 2001
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last decades, fish farming has been a rapidly increasing industry in many European and North American countries. Sweden has a large potential for aquaculture, but there is also a strong concern about the effects on the environment that an increased aquaculture production may cause. This thesis focuses on the eutrophication effects of fish farming in lakes and in coastal areas of the Baltic Sea.Possible eutrophication effects related to marine fish farm emissions were found in small and semi-enclosed bays in the Åland archipelago of the Baltic Sea. Fish farming did not have any measurable large scale effect on TN in the Åland archipelago, but there were indications of a large scale effect on TP.Nutrient concentrations and other eutrophication indicators in lakes with fish farms correlated well with the variations in farm load among the lakes and with distance from the fish farms within lakes. In a majority of the observed cases the effects on phosphorus concentrations were smaller than expected from the most commonly used models. Besides overestimating the effects, these old models described the variation between lakes adequately. It was therefore possible to construct farm specific steady state models based on the same model structures, that should be simple and accurate enough to be useful.The observed effects on phosphorus concentrations tended to be higher in lakes where fish farms had been active for a long time, compared to lakes with new fish farms. Earlier investigations have shown that there is a considerable time lag in the response of changed phosphorus loads in many lakes. Empirical data and model simulations suggest that this is the case also for fish farm lakes.
|
|
| 3. |
|
|
| 4. |
- Karlsson-Elfgren, Irene, et al.
(författare)
-
Recruitment and pelagic growth of Gloeotrichia echinulata (Chyanophyceae) in Lake Erken
- 2003
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 39:6, s. 1050-1056
-
Tidskriftsartikel (refereegranskat)abstract
- Different parameters in the life cycle of the colony forming cyanobacterium Gloeotrichia echinulata (J.E. Smith) Richter was evaluated in Lake Erken, Sweden. Recruitment of colonies from the sediments and pelagic abundance were measured during 2 years. These data were then used in a model to evaluate and estimate parameters of the life cycle. In our study, recruitment alone only contributed to a small part (<5%) of the maximum G. echinulata abundance that occurred during late summer. However, recruitment from shallow sediments forms the important seed for the pelagic population. Together with measured rates of migration from the sediment, variations in either pelagic colony division rate or pelagic residence time could explain variations in the measured abundance of G. echinulata in situ.
|
|
| 5. |
- Karlsson Elfgren, Irene
(författare)
-
Studies on the Life Cycles of Akinete Forming Cyanobacteria
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cyanobacteria which can form resting cells (in this case akinetes) are common in meso-eutrophic lakes in temperate regions, often dominating the phytoplankton communities during summer. The life cycles of akinete-forming cyanobacteria has been studied with Gloeotrichia echinulata as a model organism. Anabaena and Aphanizomenon were also included in a migration study. The focus of this thesis has been the factors influencing the processes of germination and subsequent growth, the factors influencing migration from the sediment, and the amount of growth occurring in the water. Germination of G. echinulata was strongly favoured by light, and recruitment was highest from organic-rich sediments in shallow, sheltered littoral areas, between 0-3 m. Recruitment of Anabaena and Aphanizomenon was less light dependent, yet the highest recruitment occurred from shallow sediments (0-2 m). This means that organic-rich sediments (0-3 m) in shallow areas are the most important seed-banks of akinete-forming cyanobacteria. The inocula contributed only to a minor extent to the maximum pelagic populations. 4% for G. echinulata in the mesotrophic Lake Erken, and 0.03% for both Anabaena and Aphanizomenon in the eutrophic Lake Limmaren. This implies that processes of growth and division in the water are important for the maximum size of the pelagic population. Prolonged recruitment from the sediment strongly promoted establishment of the species in the water, especially G. echinulata.
|
|
| 6. |
- Malmaeus, Jan Mikael, 1971-
(författare)
-
Predictive Modeling of Lake Eutrophication
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents predictive models for important variables concerning eutrophication effects in lakes. The keystone is a dynamic phosphorus model based on ordinary differential equations. By calculating mass fluxes of phosphorus into, within and out from a lake, the concentrations of different forms of phosphorus in different compartments of the lake are estimated.The dynamic phosphorus model is critically tested and several improvements are presented, including two new compartments for colloidal phosphorus, a sub-model for suspended particulate matter (SPM) and new algorithms for lake outflow, water mixing, diffusion, water content and organic content of accumulation sediments are implemented. Predictions with the new version show good agreement against empirical data in five tested lakes.The sub-model for SPM uses the same driving variables as the basic phosphorus model, so the inclusion of this model as a sub-model does not require any additional variables. The model for SPM may also be used as a separate model giving monthly predictions of suspended particulate matter in two water compartments and one compartment with SPM available for resuspension in ET-sediments.Empirical data from Lake Erken (Sweden) and Lake Balaton (Hungary) are used to evaluate the variability in settling velocity of SPM. It is found that the variability is substantial and may be accounted for by using a dimensionless moderator for SPM concentration. Empirical data from accumulation area sediments in Lake Erken are used to develop a model for the dynamics of phosphorus sedimentation, burial and diffusion in the sediments. The model is shown to provide reasonable monthly predictions of four functional forms of phosphorus at different sediment depths.Simulations with the lake phosphorus model using two different climate scenarios indicate that lakes may respond very differently to climate change depending on their physical character. Lake Erken, with a water retention time of 7 years, appears to be much more sensitive than two basins of Lake Mälaren (Sweden) with substantially shorter retention times. The implication would be that in eutrophic lakes with long water retention times, eutrophication problems may become serious if the future becomes warmer. This will be important in contexts of lake management when remedial measures against lake eutrophication have to be taken.
|
|
| 7. |
- Pettersson, Kurt, et al.
(författare)
-
Arthrodesis for chronic static scapholunate dissociation : a prospective study in 12 patients
- 2004
-
Ingår i: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery. - Oslo : Taylor & Francis. - 0284-4311 .- 1651-2073. ; 38:3, s. 166-171
-
Tidskriftsartikel (refereegranskat)abstract
- Twelve patients had limited arthrodesis between the scaphoid and the lunate for chronic static scapho-lunate dissociation using internal plate osteosynthesis. The median time between the injury and surgery was 50 months (range 9-180). They were followed up for a year postoperatively. Preoperative symptoms were pain, functional impairment, and restricted movement. During operation the scapholunate interosseous ligament was completely torn and the scaphoid malrotated in all patients. The range of motion was measured preoperatively and postoperatively, and the unaffected side used for control. For all patients except one postoperative extension, flexion, and radial deviation had considerably decreased. However, supination increased in seven of 12 patients postoperatively and so did pronation in seven of 12 patients. One patient (case 12) had an improved range of motion postoperatively in all directions. The mean grip strength was 76% of the unaffected side preoperatively, and has increased to 85% postoperatively. We found that bone healing was rare and most arthrodeses healed by a fibrous union. We found no correlation with preoperative arthrosis and clinical outcome. One patient had retired from work before operation because of back pain and one because of age. Two patients had taken early retirement because of wrist pain, and one patient was still on sick-leave at the follow-up a year postoperatively. Five patients returned to full-time work and two patients to part-time work. Four patients were on long-term sick-leave preoperatively and three of them returned to their previous occupations. Analysis of the patients' subjective outcome (including pain and functional scores) showed overall satisfaction, and objective data show that scapholunate arthrodesis for chronic static scapholunate dissociation provides substantial improvement over the preoperative condition.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
