| 1. |
- Daewel, Ute, et al.
(författare)
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Predation control of zooplankton dynamics : a review of observations and models
- 2014
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 71:2, s. 254-271
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Forskningsöversikt (refereegranskat)abstract
- We performed a literature review to examine to what degree the zooplankton dynamics in different regional marine ecosystems across the Atlantic Ocean is driven by predation mortality and how the latter is addressed in available modelling approaches. In general, we found that predation on zooplankton plays an important role in all the six considered ecosystems, but the impacts are differently strong and occur at different spatial and temporal scales. In ecosystems with extreme environmental conditions (e.g. low temperature, ice cover, large seasonal amplitudes) and low species diversity, the overall impact of top-down processes on zooplankton dynamics is stronger than for ecosystems having moderate environmental conditions and high species diversity. In those ecosystems, predation mortality was found to structure the zooplankton mainly on local spatial and seasonal time scales. Modelling methods used to parameterize zooplankton mortality range from simplified approaches with fixed mortality rates to complex coupled multispecies models. The applicability of a specific method depends on both the observed state of the ecosystem and the spatial and temporal scales considered. Modelling constraints such as parameter uncertainties and computational costs need to be balanced with the ecosystem-specific demand for a consistent, spatial-temporal dynamic implementation of predation mortality on the zooplankton compartment.
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| 2. |
- Gårdmark, Anna, et al.
(författare)
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Biological ensemble modeling to evaluate potential futures of living marine resources
- 2013
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Ingår i: Ecological Applications. - : Wiley. - 1051-0761 .- 1939-5582. ; 23:4, s. 742-754
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Tidskriftsartikel (refereegranskat)abstract
- Natural resource management requires approaches to understand and handle sources of uncertainty in future responses of complex systems to human activities. Here we present one such approach, the biological ensemble modeling approach,'' using the Eastern Baltic cod (Gadus morhua callarias) as an example. The core of the approach is to expose an ensemble of models with different ecological assumptions to climate forcing, using multiple realizations of each climate scenario. We simulated the long-term response of cod to future fishing and climate change in seven ecological models ranging from single-species to food web models. These models were analyzed using the biological ensemble modeling approach'' by which we (1) identified a key ecological mechanism explaining the differences in simulated cod responses between models, (2) disentangled the uncertainty caused by differences in ecological model assumptions from the statistical uncertainty of future climate, and (3) identified results common for the whole model ensemble. Species interactions greatly influenced the simulated response of cod to fishing and climate, as well as the degree to which the statistical uncertainty of climate trajectories carried through to uncertainty of cod responses. Models ignoring the feedback from prey on cod showed large interannual fluctuations in cod dynamics and were more sensitive to the underlying uncertainty of climate forcing than models accounting for such stabilizing predator-prey feedbacks. Yet in all models, intense fishing prevented recovery, and climate change further decreased the cod population. Our study demonstrates how the biological ensemble modeling approach makes it possible to evaluate the relative importance of different sources of uncertainty in future species responses, as well as to seek scientific conclusions and sustainable management solutions robust to uncertainty of food web processes in the face of climate change.
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| 3. |
- MacKenzie, Brian R., et al.
(författare)
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Impact of Climate Change on Fish Population Dynamics in the Baltic Sea : A Dynamical Downscaling Investigation
- 2012
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 41:6, s. 626-636
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how climate change, exploitation and eutrophication will affect populations and ecosystems of the Baltic Sea can be facilitated with models which realistically combine these forcings into common frameworks. Here, we evaluate sensitivity of fish recruitment and population dynamics to past and future environmental forcings provided by three ocean-biogeochemical models of the Baltic Sea. Modeled temperature explained nearly as much variability in reproductive success of sprat (Sprattus sprattus; Clupeidae) as measured temperatures during 1973-2005, and both the spawner biomass and the temperature have influenced recruitment for at least 50 years. The three Baltic Sea models estimate relatively similar developments (increases) in biomass and fishery yield during twenty-first century climate change (ca. 28 % range among models). However, this uncertainty is exceeded by the one associated with the fish population model, and by the source of global climate data used by regional models. Knowledge of processes and biases could reduce these uncertainties.
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| 4. |
- Meier, H. E. Markus, et al.
(författare)
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Ensemble Modeling of the Baltic Sea Ecosystem to Provide Scenarios for Management
- 2014
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 43:1, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- We present a multi-model ensemble study for the Baltic Sea, and investigate the combined impact of changing climate, external nutrient supply, and fisheries on the marine ecosystem. The applied regional climate system model contains state-of-the-art component models for the atmosphere, sea ice, ocean, land surface, terrestrial and marine biogeochemistry, and marine food-web. Time-dependent scenario simulations for the period 1960-2100 are performed and uncertainties of future projections are estimated. In addition, reconstructions since 1850 are carried out to evaluate the models sensitivity to external stressors on long time scales. Information from scenario simulations are used to support decision-makers and stakeholders and to raise awareness of climate change, environmental problems, and possible abatement strategies among the general public using geovisualization. It is concluded that the study results are relevant for the Baltic Sea Action Plan of the Helsinki Commission.
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| 5. |
- Meier, Markus, et al.
(författare)
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Comparing reconstructed past variations and future projections of the Baltic sea ecosystem first results from multi model ensemble simulations
- 2012
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:3, s. 034005-
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Tidskriftsartikel (refereegranskat)abstract
- Multi-model ensemble simulations for the marine biogeochemistry and food web of the Baltic Sea were performed for the period 1850-2098, and projected changes in the future climate were compared with the past climate environment. For the past period 1850-2006, atmospheric, hydrological and nutrient forcings were reconstructed, based on historical measurements. For the future period 1961-2098, scenario simulations were driven by regionalized global general circulation model (GCM) data and forced by various future greenhouse gas emission and air-and riverborne nutrient load scenarios (ranging from a pessimistic 'business-as-usual' to the most optimistic case). To estimate uncertainties, different models for the various parts of the Earth system were applied. Assuming the IPCC greenhouse gas emission scenarios A1B or A2, we found that water temperatures at the end of this century may be higher and salinities and oxygen concentrations may be lower than ever measured since 1850. There is also a tendency of increased eutrophication in the future, depending on the nutrient load scenario. Although cod biomass is mainly controlled by fishing mortality, climate change together with eutrophication may result in a biomass decline during the latter part of this century, even when combined with lower fishing pressure. Despite considerable shortcomings of state-of-the-art models, this study suggests that the future Baltic Sea ecosystem may unprecedentedly change compared to the past 150 yr. As stakeholders today pay only little attention to adaptation and mitigation strategies, more information is needed to raise public awareness of the possible impacts of climate change on marine ecosystems.
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| 6. |
- Niiranen, Susa, 1982-
(författare)
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Baltic Sea food web dynamics and response to environmental change
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Baltic Sea ecosystem is subject to a combination of external pressures such as fishery, changing climate and land-based nutrient inputs. In combination with internal food web mechanisms these external forces can lead to changes in the food web structure and function. In this licentiate thesis a new Baltic Sea Ecopath with Ecosim food web model for the open Baltic Proper (BaltProWeb) is introduced as a tool to study the past (1974-2006) food web dynamics (paper 1) and the sensitivity of this model to data uncertainties is analyzed (paper 2). BaltProWeb includes 22 functional groups from phytoplankton to top-predators, is calibrated with biomass data across trophic levels and can accommodate external forcing such as fishery and environmental change. The model can reproduce the main trends observed in the biomass development of most Baltic Proper functional groups as well as the late 1980s ecosystem reorganization, or regime shift, from the cod (Gadus morhua) dominated state into the sprat (Sprattus sprattus) dominated one. In addition to changes in the functional group biomasses, changes in ecosystem flows were observed. For example the energy flow from the benthic system into the pelagic one (via cod diet) was large during the pre-regime shift period, but decreased in importance after the sharp post-regime shift increase in the sprat biomass. The proportions of both clupeid and zooplankton production required to support the Baltic Sea fisheries were large throughout the model run suggesting that fisheries have potential to be an ecosystem structuring actor in the Baltic Proper. Successful reproduction of the past biomass dynamics required the inclusion of fishery and environmental forcing together with appropriate trophic control during the calibration process. This finding motivates to develop ecosystem models that can incorporate both external pressures as well as internal ecosystem dynamics. The BaltProWeb model turned out to be sensitive to uncertainty in both model input data (1974 biomasses) as well as environmental forcing functions used. The functional groups the parameterization of which the model was most sensitive to were, in decreasing order of importance, (i) 2-3 year old cod, (ii) adult sprat, (iii) macrozoobenthos, (iv) Pseudocalanus sp. and (v) other mesozooplankton. Changing the initial biomass values of these groups within the boundaries of input data uncertainty (measured as coefficients of variation) together with model recalibration resulted in a set of new Ecosim models with a rather large range in model fit, biomass projections and trophic control. When future (2007-2100) fishery and climate change scenarios were run using the different models, and by this way taking the uncertainties in the input data into account, the range of model outcomes was yet larger than observed during the calibration period (1974-2006). This indicates that model uncertainties cannot be ignored when modeling results are used as basis for ecosystem management. Further, the results highlight that evaluating the model only based on the model fit with data is not sufficient, but also studying the realized trophic control of different models is crucial and that sensitivity analysis can actually be one tool to study possible trophic control mechanisms with. This sensitivity study gave valuable information about both the model sensitivity and the need to communicate the uncertainties when the BaltProWeb model is used in the project ECOSUPPORT to project the future climate change effects on the Baltic Sea ecosystem.
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| 7. |
- 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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| 8. |
- Niiranen, Susa, 1982-
(författare)
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Multiple forces drive the Baltic Sea food web dynamics and its response to environmental change
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Understanding the interaction of multiple drivers and their compounded effects on ecosystem dynamics is a key challenge for marine resource management. The Baltic Sea is one of the world’s seas most strongly impacted by effects from both human activities and climate. In the late 1980’s changes in climate in combination with intensive fishing initiated a reorganization of the Central Baltic Sea (CBS) food web resulting in the current sprat-dominated state. In the future, climate change is projected to cause drastic changes in hydrodynamic conditions of the world oceans in general, and the Baltic Sea in particular. In this thesis, CBS food web responses to the combined effects of fishing, nutrient loads and climate were tested for the past (1974-2006) and projected into the future (2010-2098). A new food web model for the CBS (BaltProWeb) was developed using extensive monitoring data across trophic levels. This model described the past food web dynamics well, and was hence also used for future (2010-2098) projections. Different ensemble modeling approaches were employed when testing the food web response to future scenarios.The results show that regardless the climate change, the management of nutrient loads and cod fishing are likely to determine the food web dynamics and trophic control mechanisms in the future Baltic Sea. Consequently, the variation in the food web projections was large, ranging from a strongly eutrophied and sprat-dominated to a cod-dominated CBS with eutrophication levels close to today’s values. The results also suggest a potential risk of abrupt ecosystem changes in the future CBS, particularly if the nutrient loads are not reduced. Finally, the studies illustrate the usefulness of the ensemble modeling approach, both from the perspective of ecosystem-based management as well as for studying the importance of different mechanisms in the ecosystem response.
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| 9. |
- Niiranen, Susa, et al.
(författare)
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Uncertainties in a Baltic Sea Food-Web Model Reveal Challenges for Future Projections
- 2012
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 41:6, s. 613-625
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Tidskriftsartikel (refereegranskat)abstract
- Models that can project ecosystem dynamics under changing environmental conditions are in high demand. The application of such models, however, requires model validation together with analyses of model uncertainties, which are both often overlooked. We carried out a simplified model uncertainty and sensitivity analysis on an Ecopath with Ecosim food-web model of the Baltic Proper (BaltProWeb) and found the model sensitive to both variations in the input data of pre-identified key groups and environmental forcing. Model uncertainties grew particularly high in future climate change scenarios. For example, cod fishery recommendations that resulted in viable stocks in the original model failed after data uncertainties were introduced. In addition, addressing the trophic control dynamics produced by the food-web model proved as a useful tool for both model validation, and for studying the food-web function. These results indicate that presenting model uncertainties is necessary to alleviate ecological surprises in marine ecosystem management.
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| 10. |
- Tomczak, Macief, et al.
(författare)
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Ecosystem flow dynamics in the Baltic Proper-Using a multi-trophic dataset as a basis for food-web modelling
- 2012
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 230, s. 123-147
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Tidskriftsartikel (refereegranskat)abstract
- The Baltic Proper is a semi-enclosed, highly productive basin of the Baltic Sea with a low biodiversity, where only a few key species drive the system's dynamics. Recently, an ecosystem regime shift was described having pronounced changes at all trophic levels, driven by changes in fishery and climate and leading to a food-web reorganisation. An Ecopath with Ecosim Baltic Proper food-web model (BaltProWeb) was developed to simulate and better understand trophic interactions and their flows. The model contains 22 functional groups that represent the main food-web components. BaltProWeb was calibrated to long-term monitoring data (1974-2006), covering multiple trophic levels and is forced by fisheries and environmental drivers. Our model enables the quantification of the flows through the food-web from primary producers to top predators including fisheries over time. The model is able to explain 51% of the variation in biomass of multiple trophic levels and to simulate the regime shift from a cod dominated to a sprat dominated system. Results show a change from benthic to more pelagic trophic flows. Before the reorganisation macrozoobenthos was identified as an important functional group transferring energy directly from lower trophic levels to top predators. After the regime shift, the pelagic trophic flows dominated. Uncertainties and limitations of the modelling approach and results in relation to ecosystem-based management are discussed.
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