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- Chen, Deliang, 1961, et al.
(author)
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Summary of a workshop on extreme weather events in a warming world organized by the Royal Swedish Academy of Sciences
- 2020
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In: Tellus Series B-Chemical and Physical Meteorology. - : Stockholm University Press. - 1600-0889 .- 0280-6509. ; 72:1
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Journal article (peer-reviewed)abstract
- Climate change is not only about changes in means of climatic variables such as temperature, precipitation and wind, but also their extreme values which are of critical importance to human society and ecosystems. To inspire the Swedish climate research community and to promote assessments of international research on past and future changes in extreme weather events against the global climate change background, the Earth Science Class of the Royal Swedish Academy of Sciences organized a workshop entitled 'Extreme weather events in a warming world' in 2019. This article summarizes and synthesizes the key points from the presentations and discussions of the workshop on changes in floods, droughts, heat waves, as well as on tropical cyclones and extratropical storms. In addition to reviewing past achievements in these research fields and identifying research gaps with a focus on Sweden, future challenges and opportunities for the Swedish climate research community are highlighted.
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- Forth, Michael, et al.
(author)
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Effects of ecological engineered oxygenation on the bacterial community structure in an anoxic fjord in western Sweden
- 2015
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In: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 9:3, s. 656-669
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Journal article (peer-reviewed)abstract
- Oxygen-depleted bodies of water are becoming increasingly common in marine ecosystems. Solutions to reverse this trend are needed and under development, for example, by the Baltic deep-water OXygenation (BOX) project. In the framework of this project, the Swedish Byfjord was chosen for a pilot study, investigating the effects of an engineered oxygenation on long-term anoxic bottom waters. The strong stratification of the water column of the Byfjord was broken up by pumping surface water into the deeper layers, triggering several inflows of oxygen-rich water and increasing oxygen levels in the lower water column and the benthic zone up to 110μmoll−1.We used molecular ecologic methods to study changes in bacterial community structure in response to the oxygenation in the Byfjord. Water column samples from before, during and after the oxygenation as well as from two nearby control fjords were analyzed. Our results showed a strong shift in bacterial community composition when the bottom water in the Byfjord became oxic. Initially dominant indicator species for oxygen minimum zones such as members of the SUP05 clade declined in abundance during the oxygenation event and nearly vanished after the oxygenation was accomplished. In contrast, aerobic species like SAR11 that initially were restricted to surface waters could later be detected deep into the water column. Overall, the bacterial community in the formerly anoxic bottom waters changed to a community structure similar to those found in oxic waters, showing that an engineered oxygenation of a large body of anoxic marine water is possible and emulates that of a natural oxygenation event.
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- halide, halmar, et al.
(author)
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Developing a decision support system for sustainable cage aquaculture
- 2009
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In: Environmental Modelling and Software. - : Elsevier BV. - 1364-8152. ; 24:6, s. 694-702
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Journal article (peer-reviewed)abstract
- A decision support system to assist cage aquaculture managers is presented. The system enables managers to perform four essential tasks: (i) site classification, (ii) site selection, (iii) holding capacity determination, and (iv) economic appraisal of an aquaculture farm at a given site. Based on measurements of water and substrate qualities, hydrometeorology and socioeconomic factors, a cage aquaculture site is classified into three categories – poor, medium, and good. With this information, the AHP (analytical hierarchy process) tool is used to evaluate the best site from several alternatives. A simplified version of the Modelling-On growing-Monitoring (MOM), SMOM, is developed and applied to determine how much fish can be grown on site without harming the environment. The simplified model has been calibrated against MOM, compared with other carrying capacity models and validated with farm data. A break-even point–price and return on investment (ROI) are calculated using cage-holding density and volume, mean fish weight at harvest, feed conversion ratio (FCR), survival rate of seed, costs of feed, seed and cages, the interest rate on borrowed funds and the fish price. All model components are integrated seamlessly into a user-friendly interface implemented in Java® called CADS_TOOL (Cage Aquaculture Decision Support Tool). The program with a user's guide is freely available.
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- Stigebrandt, A., et al.
(author)
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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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In: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 11:1, s. 93-110
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Journal article (peer-reviewed)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 well-oxygenated 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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- Stigebrandt, Anders, 1942, et al.
(author)
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Regulating the local environmental impact of intensive marine fish farming - III. A model for estimation of the holding capacity in the Modelling-Ongrowing fish farm-Monitoring system
- 2004
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In: Aquaculture. - : Elsevier BV. - 0044-8486. ; 234:1-4, s. 239-261
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Journal article (peer-reviewed)abstract
- A model has been developed for estimating the holding capacity of sites for fish farming. Expressed in terms of maximum fish production per month, the holding capacity is estimated with regard to three basic environmental requirements: (i) the benthic fauna at a farm site must not be allowed to disappear due to accumulation of organic material; (ii) the water quality in the net pens must be kept high; (iii) the water quality in the areas surrounding the farm must not deteriorate. All these requirements must be fulfilled, and the holding capacity is determined by the lowest of the three estimates. The fulfillment of requirements (i) and (ii) depends on local environmental properties such as water depth, the annual temperature cycle and the vertical distribution of current properties, and concentrations of oxygen and ammonium. It also depends on the maximum fish density per unit area, so the physical configuration of the farm is of importance. All these factors as well as feeding rate and feed composition are taken into account in the model. The model comprises four sub-models which, for a given set of local environmental parameters, compute holding capacity according to these basic requirements. Given the feeding rate, feed composition and water temperature, a general fish sub-model adapted for domesticated Atlantic salmon computes the metabolism, growth and feed requirement of a specified fish stock. The fish model also computes emissions of particulate organic matter, i.e., uneaten feed and faeces. A dispersion sub-model computes the distribution of particulate matter from the net pens on the bottom for various sizes of pens and distances between them. A benthic sub-model computes the maximum rate of particulate matter sedimentation that will not result in the extinction of the benthic macro infauna. Water quality in the net pens is expressed as the lowest concentration of oxygen and the highest concentration of dissolved substances potentially harmful to the fish. These are computed by the water quality sub-model that needs input from the fish sub-model concerning the emission of dissolved substances and the consumption of oxygen due to respiration. The holding capacity according to requirement (iii) is computed by means of a previously published model. (C) 2004 Elsevier B.V. All rights reserved.
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