| 1. |
- Eglite, Elvita, et al.
(författare)
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Nutrient turnover at the hypoxic boundary : flux measurements and model representation for the bottom water environment of the Gulf of Riga, Baltic Sea
- 2014
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Ingår i: Oceanologia. - : Elsevier BV. - 0078-3234. ; 56:4, s. 711-735
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Tidskriftsartikel (refereegranskat)abstract
- Experimental studies of intact sediment cores from the Gulf of Riga, Baltic Sea, were conducted to estimate the response of sediment nutrient fluxes to various near-bottom water oxygen conditions. The experiment was performed in the laboratory using a batch-mode assay type system on the sediment cores held at 4 degrees C and oxygen concentrations maintained at 1, 2, 3, 4 and 5 mg l(-1). The results from the experiment were subsequently used to optimise the fit of the sediment denitrification sub-model of the Gulf of Riga basin. Sedimentwater fluxes of phosphate were low and directed out of the sediments under all treatments, demonstrating a general decreasing tendency with increasing near-bottom water oxygen concentration. The sediment-water fluxes of ammonium and nitrate + nitrite demonstrated opposing trends: ammonium fluxes decreased whereas nitrate + nitrite fluxes increased with rising near-bottom water oxygen concentration. The modelled fluxes agreed well with the measured ones, with correlation coefficients of 0.75, 0.63 and 0.88 for ammonium, nitrate + nitrite and phosphate fluxes respectively. The denitrification rate in sediments was simulated at oxygen concentrations from -2 to 10 mg l(-1). At oxygen concentrations < 2 mg l(-1) the modelled denitrification was sustained by nitrate transport from water overlying the sediments. With increasing oxygen concentrations the simulated denitrification switched from the process fuelled by nitrates originating from the overlying water (D-w) to one sustained by nitrates originating from the coupled sedimentary nitrification - denitrification (D-n). D-n reached its maximum at an oxygen concentration of 5 mg l(-1).
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| 2. |
- Meier, Markus, et al.
(författare)
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Hypoxia in future climates : a model ensemble study for the Baltic Sea
- 2011
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 38, s. L24608-
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Tidskriftsartikel (refereegranskat)abstract
- Using an ensemble of coupled physical-biogeochemical models driven with regionalized data from global climate simulations we are able to quantify the influence of changing climate upon oxygen conditions in one of the numerous coastal seas (the Baltic Sea) that suffers worldwide from eutrophication and from expanding hypoxic zones. Applying various nutrient load scenarios we show that under the impact of warming climate hypoxic and anoxic areas will very likely increase or at best only slightly decrease (in case of optimistic nutrient load reductions) compared to present conditions, regardless of the used global model and climate scenario. The projected decreased oxygen concentrations are caused by (1) enlarged nutrient loads due to increased runoff, (2) reduced oxygen flux from the atmosphere to the ocean due to increased temperature, and (3) intensified internal nutrient cycling. In future climate a similar expansion of hypoxia as projected for the Baltic Sea can be expected also for other coastal oceans worldwide.
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| 3. |
- Moellmann, Christian, et al.
(författare)
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Implementing ecosystem-based fisheries management : from single-species to integrated ecosystem assessment and advice for Baltic Sea fish stocks
- 2014
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 71:5, s. 1187-1197
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Tidskriftsartikel (refereegranskat)abstract
- Theory behind ecosystem-based management (EBM) and ecosystem-based fisheries management (EBFM) is now well developed. However, the implementation of EBFM exemplified by fisheries management in Europe is still largely based on single-species assessments and ignores the wider ecosystem context and impact. The reason for the lack or slow implementation of EBM and specifically EBFM is a lack of a coherent strategy. Such a strategy is offered by recently developed integrated ecosystem assessments (IEAs), a formal synthesis tool to quantitatively analyse information on relevant natural and socio-economic factors, in relation to specified management objectives. Here, we focus on implementing the IEA approach for Baltic Sea fish stocks. We combine both tactical and strategic management aspects into a single strategy that supports the present Baltic Sea fish stock advice, conducted by the International Council for the Exploration of the Sea (ICES). We first review the state of the art in the development of IEA within the current management framework. We then outline and discuss an approach that integrates fish stock advice and IEAs for the Baltic Sea. We intentionally focus on the central Baltic Sea and its three major fish stocks cod (Gadus morhua), herring (Clupea harengus), and sprat (Sprattus sprattus), but emphasize that our approach may be applied to other parts and stocks of the Baltic, as well as other ocean areas.
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| 4. |
- Müller-Karulis, Bärbel, et al.
(författare)
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Challenges and opportunities of local fisheries management : pikeperch, Sander lucioperca (Actinopterygii: Perciformes: Percidae), in Pärnu Bay, northern Gulf of Riga, Baltic Sea
- 2013
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Ingår i: Acta Ichthyologica et Piscatoria. - 0137-1592 .- 1734-1515. ; 43:2, s. 151-161
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Tidskriftsartikel (refereegranskat)abstract
- Background. A local stock of pikeperch, Sander lucioperca (Linnaeus, 1758), is a valuable fishery resource in Parnu Bay, northern Gulf of Riga. Due to the late maturity of pikeperch in the bay, the stock is vulnerable to over-exploitation, whereas recruitment is highly dependent on climate factors. Because of its high market price, fishing pressure on the stock increased considerably in the 1990s, resulting in stock depression. To assist fishery management in Parnu Bay we have simulated the effect of several scenarios (such as: fishing mortality, climate, and young-of-the-year food supply) on the pikeperch stock, catches, and revenues generated by the fishery.Materials and methods. A simulation system consisting of an age-structured population model, a recruitment component, and a forcing module of different climate, food supply to young-of-the-year, and fishing mortality scenarios was used to estimate the equilibrium stock size and catches under varying environmental conditions and exploitation strategies. Economic impacts of these scenarios were assessed based on the first selling price of pikeperch.Results. Under present climate and food supply for pikeperch young-of-the-year, the Parnu Bay pikeperch stock is very sensitive to catches of immature fish. Warmer future climate conditions are likely to be beneficial for the stock, but also prey abundance for young-of-the-year influences potential stock sizes and catches. Compared to targeting its prey species, herring, which has a lower commercial value at current first selling prices, pikeperch acts as a biomeliorator, roughly doubling fisheries revenue in the bay.Conclusion. Flexible adaptive management methods should be used to estimate the yearly allowable pikeperch catch, taking into account food supply to young-of-the-year and climate conditions influencing recruitment.
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| 5. |
- Müller-Karulis, Bärbel, et al.
(författare)
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Modeling the long-term dynamics of nutrients and phytoplankton in the Gulf of Riga
- 2011
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 87:3-4, s. 161-176
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Tidskriftsartikel (refereegranskat)abstract
- The long term dynamics of nitrogen, phosphorus, and phytoplankton in the Gulf of Riga were simulated with a biogeochemical box model that resolved seasonal cycles. The model was calibrated using a numerical optimization procedure that adjusted 37 parameters to maximize the model data fit for field observations from 1973 to 2000 and validated with an independent dataset covering 2001-2007. Both the long-term increase and subsequent decline in winter nitrogen concentrations, as well as the continuous increase in winter phosphate levels were well reproduced by the model, which also gave reasonable representations of the seasonal dynamics of nutrients and phytoplankton. Starting from the mid-1990s, the model simulated an increase in cyanobacteria growth sustained by internal phosphorus loading. While nitrogen was efficiently removed by denitrification from the Gulf of Riga, comparatively slow export to the Baltic Proper was the main removal pathway of phosphorus. Modeled residence times were 5.4 years for nitrogen and 38 years for phosphorus. Scenario simulations indicated that the Gulf of Riga responds to phosphorus load reductions with a gradual decrease in primary production and cyanobacteria growth, while the effect of nitrogen load reductions is largely offset by nitrogen fixation.
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| 6. |
- Müller-Karulis, Bärbel, et al.
(författare)
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Secchi depth calculations in BALTSEM
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Secchi depth measurements have been carried out for over 100 years in the Baltic Sea and the changes in Secchi depth give indications of the development of phytoplankton biomass in response to eutrophication. In the implementation of the ecosystem approach to Baltic Sea management, indicators based on Secchi depth are unique in that targets representing a good environmental status can be obtained from actual observations, whereas most other indicators lack observational evidence of a reference state representing conditions before substantial eutrophication. In the on‐going revision of the HELCOM Baltic Sea Action Plan, new targets on e.g., Secchi depth have been developed (HELCOM2012). The following step is to use modeling to find nutrient inputs to the Baltic Sea, so called Maximum Allowable Inputs, that result in ecosystem changes so that eventually the good environmental status indicated by the targets is reached. This modeling effort is carried out using the coupled physical‐biogeochemical model BALTSEM developed at BNI. The BALTSEM model resolves the Baltic Sea horizontally with 13 sub‐basins, but each of these with high vertical resolution. The biogeochemical model includes inorganic and bioavailable organic nitrogen, phosphorus and silica, three phytoplankton groups, zooplankton and oxygen. Benthic nutrient regeneration and retention are modeled in addition. This report describes a statistical post‐processing algorithm to calculate Secchi depth from BALTSEM results to provide additional accuracy and confidence of Secchi depth estimates compared to the simplistic intrinsic transparency calculations within the BALTSEM model. The additional quality in the Secchi depth calculation results isof major importance for the results of the calculation of the Maximum Allowable Inputs.
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| 7. |
- Neumann, Thomas, et al.
(författare)
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Extremes of Temperature, Oxygen and Blooms in the Baltic Sea in a Changing Climate
- 2012
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 41:6, s. 574-585
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Tidskriftsartikel (refereegranskat)abstract
- In the future, the Baltic Sea ecosystem will be impacted both by climate change and by riverine and atmospheric nutrient inputs. Multi-model ensemble simulations comprising one IPCC scenario (A1B), two global climate models, two regional climate models, and three Baltic Sea ecosystem models were performed to elucidate the combined effect of climate change and changes in nutrient inputs. This study focuses on the occurrence of extreme events in the projected future climate. Results suggest that the number of days favoring cyanobacteria blooms could increase, anoxic events may become more frequent and last longer, and salinity may tend to decrease. Nutrient load reductions following the Baltic Sea Action Plan can reduce the deterioration of oxygen conditions.
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| 8. |
- Niiranen, Susa, et al.
(författare)
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Combined effects of global climate change and regional ecosystem drivers on an exploited marine food web
- 2013
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 19:11, s. 3327-3342
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Tidskriftsartikel (refereegranskat)abstract
- Changes in climate, in combination with intensive exploitation of marine resources, have caused large-scale reorganizations in many of the world's marine ecosystems during the past decades. The Baltic Sea in Northern Europe is one of the systems most affected. In addition to being exposed to persistent eutrophication, intensive fishing, and one of the world's fastest rates of warming in the last two decades of the 20th century, accelerated climate change including atmospheric warming and changes in precipitation is projected for this region during the 21st century. Here, we used a new multi-model approach to project how the interaction of climate, nutrient loads and cod fishing may affect the future of the open Central Baltic Sea food web. Regionally downscaled global climate scenarios were, in combination with three nutrient load scenarios, used to drive an ensemble of three regional biogeochemical models (BGMs). An Ecopath with Ecosim food web model was then forced with the BGM results from different nutrient-climate scenarios in combination with two different cod fishing scenarios. The results showed that regional management is likely to play a major role in determining the future of the Baltic Sea ecosystem. By the end of the 21st century, for example, the combination of intensive cod fishing and high nutrient loads projected a strongly eutrophicated and sprat-dominated ecosystem, while low cod fishing in combination with low nutrient loads resulted in a cod-dominated ecosystem with eutrophication levels close to present. Also, non-linearities were observed in the sensitivity of different trophic groups to nutrient loads or fishing depending on the combination of the two. Finally, many climate variables and species biomasses were projected to levels unseen in the past. Hence, the risk for ecological surprises needs to be addressed, particularly when the results are discussed in the ecosystem-based management context.
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| 9. |
- Savchuk, Oleg P., et al.
(författare)
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BALTSEM - a marine model for decision support within the Baltic Sea Region
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A longstanding recognition of eutrophication as the most common threat to the entire Baltic Sea has led to the international agreement on nutrient load reductions within the Baltic Sea Action Plan. The nutrient load reductions were based on quantitative estimates of the “maximum allowed nutrient inputs” evaluated with a help of the decision support system (DSS) Baltic Nest developed within the MARE (Marine Research on Eutrophication) program.As demonstrated by a comparison to available data derived from observations, the marine biogeochemical model SANBALTS (Simple As Necessary Baltic Long-Term large-Scale) used in this evaluationis capable to realistically simulate both contemporary and pre-industrial trophic states of the Baltic Sea. A key to successful performance of SANBALTS lays in accounting for major sources and sinks that determine the size of internal nutrient pools and, thus, govern the large scale Baltic Sea eutrophication. Particularly, the most important phenomena that have to be reproduced by eutrophication models are a) spatial gradients of environmental conditions and limiting nutrients, b) interconnectivity of the major Baltic Sea basins, c) sporadic ventilation of the hypoxia prone deep-water layers with saltwater inflows, d) redox alterations of the coupled nitrogen and phosphorusbiogeochemical cycles, and d) nitrogen fixationby cyanobacteria.At the same time, both a ratherhigh aggregation of ecosystem variables (organic and inorganic forms of nutrients without explicit description of biota) and their correspondent spatial-temporal averaging (annual within homogeneous basins) implemented in SANBALTS make this model not appropriate enough for further revision and elaboration of the BSAP.Because such revision has also to take into consideration indicators required by the Marine Strategy Framework Directive (MSFD) of the European Union and characterized by higher spatial and temporal resolution, e.g.basin-wise winter surface nutrient concentrations and summer phytoplankton biomasses, and because of a necessity to factor in the possible effects of climate fluctuations, the appropriate model must simulate changes in ecosystem seasonal dynamics occurring over tens of years in response to both nutrient load reductions and climate changes. In principle, the continuing development of computing resources has made it feasible to implement for such purposes three-dimensional coupled physical-biogeochemical models with a relatively high resolution.However, with such models a simulation of the entire Baltic Sea over several decades still requires many days of computation even at super computer centers, which greatly hinders numerical experimentation needed for both model calibration and sensitivity analysis, including scenario responses. Therefore, there is a need for the model that is both reliable and convenient enough to be used for the revision of BSAP and implementation of MSFD,as well as for similar managerial tasks within an ecosystem approach. To serve this need, the model should be computationally fast for allowing multiple numerical runs necessary for finding and testing suitable distributions of the water-protection measures. Furthermore, for a building of credibility necessary in the national deliberations and international negotiations it should also be publicly accessible through the decision support system Nest allowing to any interested party running hindcast and scenario experiments as well as visualize its results. For these purposes, we present here the latest developments of the BAltic sea Long-Term large Scale Eutrophication Model (BALTSEM), which captures the main features of the Baltic Sea eutrophication, and now servesas a next generation marine model in the Baltic Nest system. These results as well as hindcast for 1850-2006 and future scenarios can be reproduced and analyzed on-line. Since BALTSEM performance at long-term scales has already been presented by Eilola et al. (2011a) and Gustafsson et al. (2012), this paper is especially focused on a seasonal scale.
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| 10. |
- Österblom, Henrik, et al.
(författare)
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Modeling Social—Ecological Scenarios in Marine Systems
- 2013
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Ingår i: BioScience. - : Oxford University Press (OUP). - 0006-3568 .- 1525-3244. ; 63:9, s. 735-744
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Tidskriftsartikel (refereegranskat)abstract
- Human activities have substantial impacts on marine ecosystems, including rapid regime shifts with large consequences for human well-being. We highlight the use of model-based scenarios as a scientific tool for adaptive stewardship in the face of such consequences. The natural sciences have a long history of developing scenarios but rarely with an in-depth understanding of factors influencing human actions. Social scientists have traditionally investigated human behavior, but scholars often argue that behavior is too complex to be repre-ented by broad generalizations useful for models and scenarios. We address this scientific divide with a framework for integrated marine social ecological scenarios, combining quantitative process-based models from the biogeochemical and ecological disciplines with qualitative studies on governance and social change. The aim is to develop policy-relevant scenarios based on an in-depth empirical understanding from both the natural and the social sciences, thereby contributing to adaptive stewardship of marine social-ecological systems.
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