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  • 1.
    Alling, Vanja
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Porcelli, D.
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Anderson, L. G.
    Sanchez-Garcia, L.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Gustafsson, Örjan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Andersson, P. S.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Degradation of terrestrial organic carbon, primary production and out-gassing of CO2 in the Laptev and East Siberian Seas as inferred from delta C-13 values of DIC2012Ingår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 95, s. 143-159Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The cycling of carbon on the Arctic shelves, including outgassing of CO2 to the atmosphere, is not clearly understood. Degradation of terrestrial organic carbon (OCter) has recently been shown to be pronounced over the East Siberian Arctic Shelf (ESAS), i.e. the Laptev and East Siberian Seas, producing dissolved inorganic carbon (DIC). To further explore the processes affecting DIC, an extensive suite of shelf water samples were collected during the summer of 2008, and assessed for the stable carbon isotopic composition of DIC (delta C-13(DIC)). The delta C-13(DIC) values varied between -7.2 parts per thousand to +1.6 parts per thousand and strongly deviated from the compositions expected from only mixing between river water and seawater. Model calculations suggest that the major processes causing these deviations from conservative mixing were addition of (DIC) by degradation of OCter, removal of DIC during primary production, and outgassing of CO2. All waters below the halocline in the ESAS had delta C-13(DIC) values that appear to reflect mixing of river water and seawater combined with additions of on average 70 +/- 20 mu M of DIC, originating from degradation of OCter in the coastal water column. This is of the same magnitude as the recently reported deficits of DOCter and POCter for the same waters. The surface waters in the East Siberian Sea had higher delta C-13(DIC) values and lower DIC concentrations than expected from conservative mixing, consistent with additions of DIC from degradation of OCter and outgassing of CO2. The outgassing of CO2 was equal to loss of 123 +/- 50 mu M DIC. Depleted delta C-13(POC) values of -29 parts per thousand to -32 parts per thousand in the mid to outer shelf regions are consistent with POC from phytoplankton production. The low delta C-13(POC) values are likely due to low delta C-13(DIC) of precursor DIC, which is due to degradation of OCter, rather than reflecting terrestrial input compositions. Overall, the delta C-13(DIC) values confirm recent suggestions of substantial degradation of OCter over the ESAS, and further show that a large part of the CO2 produced from degradation has been outgassed to the atmosphere.

  • 2. Andersen, Jesper H.
    et al.
    Carstensen, Jacob
    Conley, Daniel J.
    Dromph, Karsten
    Fleming-Lehtinen, Vivi
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Josefson, Alf B.
    Norkko, Alf
    Villnäs, Anna
    Murray, Ciarán
    Long-term temporal and spatial trends in eutrophication status of the Baltic Sea2017Ingår i: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 92, nr 1, s. 135-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Much of the Baltic Sea is currently classified as 'affected by eutrophication'. The causes for this are twofold. First, current levels of nutrient inputs (nitrogen and phosphorus) from human activities exceed the natural processing capacity with an accumulation of nutrients in the Baltic Sea over the last 50-100 years. Secondly, the Baltic Sea is naturally susceptible to nutrient enrichment due to a combination of long retention times and stratification restricting ventilation of deep waters. Here, based on a unique data set collated from research activities and long-term monitoring programs, we report on the temporal and spatial trends of eutrophication status for the open Baltic Sea over a 112-year period using the HELCOM Eutrophication Assessment Tool (HEAT 3.0). Further, we analyse variation in the confidence of the eutrophication status assessment based on a systematic quantitative approach using coefficients of variation in the observations. The classifications in our assessment indicate that the first signs of eutrophication emerged in the mid-1950s and the central parts of the Baltic Sea changed from being unaffected by eutrophication to being affected. We document improvements in eutrophication status that are direct consequences of long-term efforts to reduce the inputs of nutrients. The reductions in both nitrogen and phosphorus loads have led to large-scale alleviation of eutrophication and to a healthier Baltic Sea. Reduced confidence in our assessment is seen more recently due to reductions in the scope of monitoring programs. Our study sets a baseline for implementation of the ecosystem-based management strategies and policies currently in place including the EU Marine Strategy Framework Directives and the HELCOM Baltic Sea Action Plan.

  • 3.
    Andrejev, Oleg
    et al.
    Finnish Environment Institute.
    Sokolov, Alexander
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Soomere, Tarmo
    Institute of Cybernetics.
    Värv, Rolf
    Institute of Cybernetics.
    Viikmäe, Bert
    Institute of Cybernetics.
    The use of high-resolution bathymetry for circulation modelling in the Gulf of Finland2010Ingår i: Estonian Journal of Engineering, Vol. 16, nr 3, s. 187-210Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present preliminary results of the extension of the OAAS circulation model to a high-resolution bathymetry with a finest resolution of 0.25 nautical miles in the Gulf of Finland, the Baltic Sea. The models with a resolution of 1 mile or finer are capable of resolving typical mesoscale eddies in this basin where the internal Rossby radius is usually 2–4 km. An increase in the model resolution from 1 to 0.5 NM leads to a clear improvement of the representation of the key hydrophysical fields. A further increase in the resolution to 0.25 NM has a lesser impact on hydro­physical fields, but may lead to some changes in the instantaneous patterns of currents. The para­meterization of the spreading effect of sub-grid-scale turbulence on the trajectories of initially closely located drifters is realized by means of accounting for the largely rotational character of the dynamics in this basin. The modelled average spreading rate for initially closely located particles for 1991 was 2 mm/s.

  • 4. Andrejev, Oleg
    et al.
    Soomere, Tarmo
    Sokolov, Alexander
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Myrberg, Kai
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    The role of the spatial resolution of a three-dimensional hydrodynamic model for marine transport risk assessment2011Ingår i: Oceanologia, ISSN 0078-3234, Vol. 53, nr 1, s. 309-334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper addresses the sensitivity of a novel method for quantifying the environmental risks associated with the current-driven transport of adverse impacts released from offshore sources (e.g. ship traffic) with respect to the spatial resolution of the underlying hydrodynamic model. The risk is evaluated as the probability of particles released in different sea areas hitting the coast and in terms of the time after which the hit occurs (particle age) on the basis of a statistical analysis of large sets of 10-day long Lagrangian trajectories calculated for 1987-1991 for the Gulf of Finland, the Baltic Sea. The relevant 21) maps are calculated using the OAAS model with spatial resolutions of 2, 1 and 0.5 nautical miles (nm) and with identical initial, boundary and forcing conditions from the Rossby Centre 3D hydrodynamic model (RCO, Swedish Meteorological and Hydrological Institute). The spatially averaged values of the probability and particle age display hardly any dependence on the resolution. They both reach almost identical stationary levels (0.67-0.69 and ca 5.3 days respectively) after a few years of simulations. Also, the spatial distributions of the relevant fields are qualitatively similar for all resolutions. In contrast, the optimum locations for fairways depend substantially on the resolution, whereas the results for the 2 nm model differ considerably from those obtained using finer-resolution models. It is concluded that eddy-permitting models with a grid step exceeding half the local baroclinic Rossby radius are suitable for a quick check of whether or not any potential gain from this method is feasible, whereas higher-resolution simulations with eddy-resolving models are necessary for detailed planning. The asymptotic values of the average probability and particle age are suggested as an indicator of the potential gain from the method in question and also as a new measure of the vulnerability of the nearshore of water bodies to offshore traffic accidents.

  • 5.
    Barthel, Stephan
    et al.
    Stockholms universitet, Stockholm Resilience Centre.
    Colding, Johan
    Stockholms universitet, Stockholm Resilience Centre.
    Ernstson, Henrik
    Stockholms universitet, Stockholm Resilience Centre.
    Eriksson, Hanna
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Chans att sätta Stockholm på kartan2011Ingår i: Svenska DagbladetArtikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Så beskriver ett antal forskare från Stockholm Resilience Centre och KTH läget nu när Albano ska utvecklas till ett nytt universitetsområde. Albano kan bli en internationell förebild när det gäller hållbart byggande om politikerna tar sitt ansvar, skriver forskarna i en debattartikel i Svenska Dagbladet idag. På Stockholm Resilience Centres webbplats finns texten även på engelska.

  • 6.
    Boonstra, Wiebren J.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre, Baltic Nest Institute. University of Oslo, Norway.
    de Boer, Florianne W.
    The Historical Dynamics of Social-Ecological Traps2014Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, nr 3, s. 260-274Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Environmental degradation is a typical unintended outcome of collective human behavior. Hardin's metaphor of the tragedy of the commons has become a conceived wisdom that captures the social dynamics leading to environmental degradation. Recently, traps has gained currency as an alternative concept to explain the rigidity of social and ecological processes that produce environmental degradation and livelihood impoverishment. The trap metaphor is, however, a great deal more complex compared to Hardin's insight. This paper takes stock of studies using the trap metaphor. It argues that the concept includes time and history in the analysis, but only as background conditions and not as a factor of causality. From a historical-sociological perspective this is remarkable since social-ecological traps are clearly path-dependent processes, which are causally produced through a conjunction of events. To prove this point the paper conceptualizes social-ecological traps as a process instead of a condition, and systematically compares history and timing in one classic and three recent studies of social-ecological traps. Based on this comparison it concludes that conjunction of social and environmental events contributes profoundly to the production of trap processes. The paper further discusses the implications of this conclusion for policy intervention and outlines how future research might generalize insights from historical-sociological studies of traps.

  • 7.
    Boonstra, Wiebren J.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre, Baltic Nest Institute.
    Joosse, Sofie
    The Social Dynamics of Degrowth2013Ingår i: Environmental Values, ISSN 0963-2719, E-ISSN 1752-7015, Vol. 22, nr 2, s. 171-189Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Degrowth cannot be realised from within a capitalist society, since growth is the sine qua non for capitalism. But, societies are no blank slates; they are not built from scratch. Putting these two thoughts together seems to make degrowth logically impossible. In this paper we argue that this paradox can be solved with the use of classical and contemporary concepts from the social sciences. We illustrate the use of these concepts with reference to studies on current practices and patterns of food production and consumption. The concept of social mechanism is used to illustrate how social practices can simultaneously reinforce and challenge the dominant (food) regime. We argue that current discussions on degrowth fail to envision how such contrasting developments are linked, and that the degrowth paradox originates in the idea of capitalism and the steady-state economy as alternative systems. The paradox dissolves with studies of mechanisms and social practices that show how the two systems are not autonomous, but 'hybridised' and come into existence and gain shape as reactions to each other.

  • 8. Carstensen, Jacob
    et al.
    Andersen, Jesper H.
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Conley, Daniel J.
    Deoxygenation of the Baltic Sea during the last century2014Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, nr 15, s. 5628-5633Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Deoxygenation is a global problem in coastal and open regions of the ocean, and has led to expanding areas of oxygen minimum zones and coastal hypoxia. The recent expansion of hypoxia in coastal ecosystems has been primarily attributed to global warming and enhanced nutrient input from land and atmosphere. The largest anthropogenically induced hypoxic area in the world is the Baltic Sea, where the relative importance of physical forcing versus eutrophication is still debated. We have analyzed water column oxygen and salinity profiles to reconstruct oxygen and stratification conditions over the last 115 y and compare the influence of both climate and anthropogenic forcing on hypoxia. We report a 10-fold increase of hypoxia in the Baltic Sea and show that this is primarily linked to increased inputs of nutrients from land, although increased respiration from higher temperatures during the last two decades has contributed to worsening oxygen conditions. Although shifts in climate and physical circulation are important factors modulating the extent of hypoxia, further nutrient reductions in the Baltic Sea will be necessary to reduce the ecosystems impacts of deoxygenation.

  • 9. Carstensen, Jacob
    et al.
    Chierici, Melissa
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. University of Helsinki, Finland.
    Gustafsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Long-Term and Seasonal Trends in Estuarine and Coastal Carbonate Systems2018Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 32, nr 3, s. 497-513Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coastal pH and total alkalinity are regulated by a diverse range of local processes superimposed on global trends of warming and ocean acidification, yet few studies have investigated the relative importance of different processes for coastal acidification. We describe long-term (1972-2016) and seasonal trends in the carbonate system of three Danish coastal systems demonstrating that hydrological modification, changes in nutrient inputs from land, and presence/absence of calcifiers can drastically alter carbonate chemistry. Total alkalinity was mainly governed by conservative mixing of freshwater (0.73-5.17mmolkg(-1)) with outer boundary concentrations (similar to 2-2.4mmolkg(-1)), modulated seasonally and spatially (similar to 0.1-0.2mmolkg(-1)) by calcifiers. Nitrate assimilation by primary production, denitrification, and sulfate reduction increased total alkalinity by almost 0.6mmolkg(-1) in the most eutrophic system during a period without calcifiers. Trends in pH ranged from -0.0088year(-1) to 0.021year(-1), the more extreme of these mainly driven by salinity changes in a sluice-controlled lagoon. Temperature increased 0.05 degrees Cyr(-1) across all three systems, which directly accounted for a pH decrease of 0.0008year(-1). Accounting for mixing, salinity, and temperature effects on dissociation and solubility constants, the resulting pH decline (0.0040year(-1)) was about twice the ocean trend, emphasizing the effect of nutrient management on primary production and coastal acidification. Coastal pCO(2) increased similar to 4 times more rapidly than ocean rates, enhancing CO2 emissions to the atmosphere. Indeed, coastal systems undergo more drastic changes than the ocean and coastal acidification trends are substantially enhanced from nutrient reductions to address coastal eutrophication.

  • 10. Carstensen, Jacob
    et al.
    Christensen, Jesper
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Gustafsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Chierici, Melissa
    Policy Brief TRIACID: Acidification in Nordic Waters: Status, trends and implications for marine species2018Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Recent studies on marine life show that the anthropogenic increase in atmospheric CO2 concentration can have negative impacts on growth and survival of groups of marine life such as corals and other calcifying organisms.

    Increased CO2 concentration in the atmosphere, and hence in the oceans, lead to decreasing pH or increasing acidification, a process known as ocean acidification (OA). During the last century, the CO2 concentration in the atmosphere has risen from around 280 ppm to 400 ppm; this has led to a pH decrease in the oceans of 0.1. OA currently takes place at a rate corresponding to approximately -0.02 pH unit per decade and an increase in CO2 at around 2 ppm per year. The projections for atmospheric CO2 concentration is an increase to around 1000 ppm at the end of the century, which will lower pH in the oceans by 0.3-0.4. Although this may appear relatively small, a decrease in pH of 0.1 corresponds to an increase in acidity (“free” protons) of 25%, and 0.3-0.4 corresponds to an increase of 200-250%.

    Coastal systems experience changes in pH over time exceeding those of the ocean by several orders of magnitude, but the field is poorly studied, and the spatial variation is large. The Baltic Sea is no exception to this. pH changes in the Baltic Sea are tightly coupled to nutrient input, alkalinity (AT) of freshwater sources in addition to increased CO2 levels and warming. Acidification trends vary substantially among coastal systems and time of year, but have been reported up to 10 times faster than OA. 

    The TRIACID project has mapped acidification trends in the Baltic Sea during the past 40 years, in different regions, and identified areas with a general lack of data. The project has described spatial variation and trends  in pH status, and the main drivers of changing pH have been identified. Given the spatial variation, the data gaps, and all the different drivers a detailed projection of the development is complicated but since we expect increasing CO2 concentration in the atmosphere, rising temperatures and decreasing nutrient input, the acidification trend will continue or accelerate in most of the region.

  • 11. Carstensen, Jacob
    et al.
    Conley, Daniel J.
    Bonsdorff, Erik
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Hietanen, Susanna
    Janas, Urzsula
    Jilbert, Tom
    Maximov, Alexey
    Norkko, Alf
    Norkko, Joanna
    Reed, Daniel C.
    Slomp, Caroline P.
    Timmermann, Karen
    Voss, Maren
    Hypoxia in the Baltic Sea: Biogeochemical Cycles, Benthic Fauna, and Management2014Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, nr 1, s. 26-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hypoxia has occurred intermittently over the Holocene in the Baltic Sea, but the recent expansion from less than 10 000 km(2) before 1950 to > 60 000 km(2) since 2000 is mainly caused by enhanced nutrient inputs from land and atmosphere. With worsening hypoxia, the role of sediments changes from nitrogen removal to nitrogen release as ammonium. At present, denitrification in the water column and sediments is equally important. Phosphorus is currently buried in sediments mainly in organic form, with an additional contribution of reduced Fe-phosphate minerals in the deep anoxic basins. Upon the transition to oxic conditions, a significant proportion of the organic phosphorus will be remineralized, with the phosphorus then being bound to iron oxides. This iron-oxide bound phosphorus is readily released to the water column upon the onset of hypoxia again. Important ecosystems services carried out by the benthic fauna, including biogeochemical feedback-loops and biomass production, are also lost with hypoxia. The results provide quantitative knowledge of nutrient release and recycling processes under various environmental conditions in support of decision support tools underlying the Baltic Sea Action Plan.

  • 12. Casini, Michele
    et al.
    Blenckner, Thorsten
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Moellmann, Christian
    Gardmark, Anna
    Lindegren, Martin
    Llope, Marcos
    Kornilovs, Georgs
    Plikshs, Maris
    Stenseth, Nils Christian
    Predator transitory spillover induces trophic cascades in ecological sinks2012Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, nr 21, s. 8185-8189Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding the effects of cross-system fluxes is fundamental in ecosystem ecology and biological conservation. Source-sink dynamics and spillover processes may link adjacent ecosystems by movement of organisms across system boundaries. However, effects of temporal variability in these cross-system fluxes on a whole marine ecosystem structure have not yet been presented. Here we show, using 35 y of multitrophic data series from the Baltic Sea, that transitory spillover of the top-predator cod from its main distribution area produces cascading effects in the whole food web of an adjacent and semi-isolated ecosystem. At varying population size, cod expand/contract their distribution range and invade/retreat from the neighboring Gulf of Riga, thereby affecting the local prey population of herring and, indirectly, zooplankton and phytoplankton via top-down control. The Gulf of Riga can be considered for cod a true sink habitat, where in the absence of immigration from the source areas of the central Baltic Sea the cod population goes extinct due to the absence of suitable spawning grounds. Our results add a metaecosystem perspective to the ongoing intense scientific debate on the key role of top predators in structuring natural systems. The integration of regional and local processes is central to predict species and ecosystem responses to future climate changes and ongoing anthropogenic disturbances.

  • 13. Conley, Daniel J.
    et al.
    Björck, Svante
    Bonsdorff, Erik
    Carstensen, Jacob
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Gustafsson, Bo G.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Hietanen, Susanna
    Kortekaas, Marloes
    Kuosa, Harri
    Meier, H. E. Markus
    Muller-Karulis, Baerbel
    Nordberg, Kjell
    Norkko, Alf
    Nurnberg, Gertrud
    Pitkänen, Heikki
    Rabalais, Nancy N.
    Rosenberg, Rutger
    Savchuk, Oleg P.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Slomp, Caroline P.
    Voss, Maren
    Wulff, Fredrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Systemekologiska institutionen. Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Zillén, Lovisa
    Hypoxia-Related Processes in the Baltic Sea2009Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, nr 10, s. 3412-3420Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP. However, both the spatial extent and intensity of hypoxia have increased with anthropogenic eutrophication due to nutrient inputs. Physical processes, which control stratification and the renewal of oxygen in bottom waters, are important constraints on the formation and maintenance of hypoxia. Climate controlled inflows of saline water from the North Sea through the Danish Straits is a critical controlling factor governing the spatial extent and duration of hypoxia. Hypoxia regulates the biogeochemical cycles of both phosphorus (P) and nitrogen (N) in the water column and sediments. Significant amounts of P are currently released from sediments, an order of magnitude larger than anthropogenic inputs. The Baltic Sea is unique for coastal marine ecosystems experiencing N losses in hypoxic waters below the halocline. Although benthic communities in the Baltic Sea are naturally constrained by salinity gradients, hypoxia has resulted in habitat loss over vast areas and the elimination of benthic fauna, and has severely disrupted benthic food webs. Nutrient load reductions are needed to reduce the extent, severity, and effects of hypoxia.

  • 14. Conley, Daniel J.
    et al.
    Bonsdorff, Erik
    Carstensen, Jacob
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Gustafsson, Bo G.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Hansson, Lars-Anders
    Rabalais, Nancy N.
    Voss, Maren
    Zillén, Lovisa
    Tackling hypoxia in the Baltic Sea: Is engineering a solution?2009Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, nr 10, s. 3407-3411Artikel i tidskrift (Refereegranskat)
  • 15. Conley, Daniel J.
    et al.
    Carstensen, Jacob
    Aigars, Juris
    Axe, Philip
    Bonsdorff, Erik
    Eremina, Tatjana
    Haahti, Britt-Marie
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Jonsson, Per
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Kotta, Jonne
    Lannegren, Christer
    Larsson, Ulf
    Stockholms universitet, Naturvetenskapliga fakulteten, Systemekologiska institutionen.
    Maximov, Alexey
    Medina, Miguel Rodriguez
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Lysiak-Pastuszak, Elzbieta
    Remeikaite-Nikiene, Nijole
    Walve, Jakob
    Stockholms universitet, Naturvetenskapliga fakulteten, Systemekologiska institutionen.
    Wilhelms, Sunhild
    Zillen, Lovisa
    Hypoxia is increasing in the coastal zone of the Baltic Sea2011Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 45, nr 16, s. 6777-6783Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hypoxia is a well-described phenomenon in the offshore waters of the Baltic Sea with both the spatial extent and intensity of hypoxia known to have increased due to anthropogenic eutrophication, however, an unknown amount of hypoxia is present in the coastal zone. Here we report on the widespread unprecedented occurrence of hypoxia across the coastal zone of the Baltic Sea. We have identified 115 sites that have experienced hypoxia during the period 1955-2009 increasing the global total to ca. 500 sites, with the Baltic Sea coastal zone containing over 20% of all known sites worldwide. Most sites experienced episodic hypoxia, which is a precursor to development of seasonal hypoxia. The Baltic Sea coastal zone displays an alarming trend with hypoxia steadily increasing with time since the 1950s effecting nutrient biogeochemical processes, ecosystem services, and coastal habitat.

  • 16.
    Deutsch, Barbara
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Alling, Vanja
    Norwegian Geotechnical Institute.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Korth, Frederike
    Leibniz Institute for Baltic Sea Research.
    Moerth, Magnus
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Tracing inputs of terrestrial high molecular weight dissolved organic matter within the Baltic Sea ecosystem2012Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 9, s. 4465-4475Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To test the hypothesis whether high molecular weight dissolved organic matter (HMW-DOM) in a high latitude marginal sea is dominated by terrestrial derived matter, 10 stations were sampled along the salinity gradient of the central and northern Baltic Sea and were analyzed for concentrations of dissolved organic carbon as well as δ13C values of HMW-DOM. Different end-member-mixing models were applied to quantify the influence of terrestrial DOM and to test for conservative versus non-conservative behavior of the terrestrial DOM in the different Baltic Sea basins. The share of terrestrial DOM to the total HMW-DOM was calculated for each station, ranging from 43 to 83%. This shows the high influence of terrestrial DOM inputs for the Baltic Sea ecosystem. The data also suggest that terrestrial DOM reaching the open Baltic Sea is not subject to substantial removal anymore. However compared to riverine DOM concentrations, our results indicate that substantial amounts of HMW-DOM (> 50%) seem to be removed near the coastline during estuarine mixing. A budget approach yielded residence times for terrestrial DOM of 2.8, 3.0, and 4.5 yr for the Bothnian Bay, the Bothnian Sea and the Baltic Proper.

  • 17. Eglite, Elvita
    et al.
    Lavrinovics, Aigars
    Muller-Karulis, Bärbel
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Latvian Institute of Aquatic Ecology, Latvia.
    Aigars, Juris
    Poikane, Rita
    Nutrient turnover at the hypoxic boundary: flux measurements and model representation for the bottom water environment of the Gulf of Riga, Baltic Sea2014Ingår i: Oceanologia, ISSN 0078-3234, Vol. 56, nr 4, s. 711-735Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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).

  • 18. Eilola, K.
    et al.
    Gustafsson, Bo G.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Kuznetsov, I.
    Meier, H. E. M.
    Neumann, T.
    Savchuk, O. P.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Evaluation of biogeochemical cycles in an ensemble of three state-of-the-art numerical models of the Baltic Sea2011Ingår i: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 88, nr 2, s. 267-284Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three state-of-the-art coupled physical-biogeochemical models, the BAltic sea Long-Term large-Scale Eutrophication Model (BALTSEM), the Ecological Regional Ocean Model (ERGOM), and the Swedish Coastal arid Ocean Biogeochemical model coupled to the Rossby Centre Ocean circulation model (RCO-SCOBI), are used to calculate changing nutrient and oxygen dynamics in the Baltic Sea. The models are different in that ERGOM and RCO-SCOBI are three-dimensional (3D) circulation models while BALTSEM resolves the Baltic Sea into 13 dynamically interconnected and horizontally integrated sub-basins. The aim is to assess the simulated long-term dynamics and to discuss the response of the coupled physical-biogeochemical models to changing physical conditions and nutrient loadings during the period 1970-2005. We compared the long-term seasonal and annual statistics of inorganic nitrogen, phosphorus, and oxygen from hindcast simulations with those estimated from observations. We also studied the extension of hypoxic bottom areas covered by waters with O(2)<2 ml O(2) l(-1) and cod reproductive volumes comprising waters with salinity >11 and O(2)>2 ml O(2) l(-1). The models reproduce much of the nutrient biogeochemical cycling in the Baltic proper. However, biases are larger in the Bothnian Sea and Bothnian Bay. No model shows outstanding performance in all aspects but instead the ensemble mean results are better than or as good as the results of any of the individual models. Uncertainties are primarily related to differences in the bioavailable fractions of nutrient loadings from land and parameterizations of key processes like sediment fluxes that are presently not well known. Also the uncertainty related to the initialization of the models in the early 1960s influence the modeled biogeochemical cycles during the investigated period.

  • 19.
    Eilola, K.
    et al.
    Swedish Meteorological and Hydrological Institute.
    Gustafsson, Bo
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Savchuck, Oleg
    Stockholms universitet, Stockholm Resilience Centre.
    Quality assessment of state-of-the-art coupled physical-biogeochemical models in hindcast simulations 1970-20052010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The objectives of the project ECOSUPPORT (Advanced modeling tool for scenarios of the Baltic Sea ECOsystem to SUPPORT decision making) are to calculate the combined effects of changing climate and changing human activity (e.g. changing nutrient loads) on the Baltic Sea ecosystem. Three state-of-the-art coupled physical-biogeochemical models (BALTSEM, ERGOM, and RCO-SCOBI) are used to calculate changing concentrations of nitrate, ammonium, phosphate, diatoms, flagellates, cyanobacteria, zooplankton, detritus, and oxygen in the Baltic Sea. The models are structurally different in that ERGOM and RCO-SCOBI are 3D circulation models with uniform high horizontal resolution while BALTSEM resolves the Baltic Sea spatially in 13 sub-basins. This report summarises first results of the quality assessment and model intercomparison within ECOSUPPORT. Results from hindcast simulations are compared with observations for the period 1970-2005. We found that all three investigated models are able to reproduce the observed variability of biogeochemical cycles well. Uncertainties are primarily related to differences in the bioavailable fractions of nutrient loadings from land and parameterizations of key processes like sediment fluxes that are presently not well known. Avsikten med projektet ECOSUPPORT (Advanced modeling tool for scenarios of the Baltic Sea ECOsystem to SUPPORT decision making) är att undersöka hur klimatförändringar tillsammans med mänsklig aktivitet (förändrad närsaltstillförsel) påverkar Östersjöns ekosystem. Tre kopplade fysiska-biogeokemiska modeller (BALTSEM, ERGOM, and RCO-SCOBI) används för att beräkna hur koncentrationer av nitrat, ammonium, fosfat, diatoméer, flagellater, cyanobakterier, djurplankton, detritus och löst syrgas i Östersjön förändras. Modellerna skiljer sig strukturellt åt genom att ERGOM och RCO-SCOBI är tredimensionella modeller med hög horisontell upplösning medan BALTSEM delar upp östersjön rumsligt i 13 delbassänger. Denna rapport sammanfattar resultaten från en första modelljämförelse och kvalitetsbedömning där modellresultat för tidsperioden 1970-2005 jämförs med observationer från samma period. Alla tre modellerna visar att de kan återskapa den observerade biogeokemiska variabiliteten väl. Osäkerheter är huvudsakligen relaterade till skillnader i andelen av näringstillförseln från land som antas vara biologiskt tillgänglig och till beskrivningarna av viktiga processer, som t.ex. flöden från sedimenten, där kunskapen för närvarande är bristfällig.

  • 20.
    Eriksson Hägg, Hanna
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Mörth, Carl- Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Rodriguez Medina, Miguel
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Scenario Analysis on Human Protein consumption and Climate change effects on riverine N export to the Balitc SeaManuskript (preprint) (Övrigt vetenskapligt)
  • 21.
    Eriksson Hägg, Hanna
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Mörth, Carl-Magnus
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Medina, Miguel Rodriguez
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Wulff, Fredrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Systemekologiska institutionen.
    Scenario Analysis on Protein Consumption and Climate Change Effects on Riverine N Export to the Baltic Sea2010Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 44, nr 7, s. 2379-2385Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper evaluates possible future nitrogen loadings from 105 catchments surrounding the Baltic Sea. Multiple regressions are used to model total nitrogen (TN) flux as a function of specific runoff (0), atmospheric nitrogen deposition, and primary emissions (PE) from humans and livestock. On average cattle contributed with 63%, humans with 20%, and pigs with 17% of the total nitrogen PE to land. Compared to the reference period (1992-1996) we then evaluated two types of scenarios for year 2070. i) An increased protein consumption scenario that led to 16% to 39% increased mean TN flux (kg per km(-2)). ii) Four climate scenarios addressing effects of changes in river discharge. These scenarios showed increased mean TN flux from the northern catchments draining into the Gulf of Bothnia (34%) and the Gulfs of Finland and Riga (14%), while the mean TN flux decreased (-27%) for catchments draining to the Baltic Proper. However, the net effect of the scenarios showed a possible increase in TN flux ranging from 3-72%. Overall an increased demand for animal protein will be instrumental for the Baltic Sea ecosystem and may be a major holdback to fulfill the environmental goals of the Baltic Sea Action Plan.

  • 22.
    Eriksson Hägg, Hanna
    et al.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Humborg, Christoph
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Swaney, D. P.
    Mörth, Carl-Magnus
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Riverine nitrogen export in Swedish catchments dominated by atmospheric inputs2012Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 111, nr 1-3, s. 203-217Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the first estimates of net anthropogenic nitrogen input (NANI) in European boreal catchments. In Swedish catchments, nitrogen (N) deposition is a major N input (31-94%). Hence, we used two different N deposition inputs to calculate NANI for 36 major Swedish catchments. The relationship between riverine N export and NANI was strongest when using only oxidized deposition (NOy) as atmospheric input (r(2) = 0.70) rather than total deposition (i.e., both oxidized and reduced nitrogen, NOy + NHx deposition, r(2) = 0.62). The y-intercept (NANI = 0) for the NANI calculated with NOy is significantly different from zero (p = 0.0042*) and indicates a background flux from the catchment of some 100 kg N km(-2) year(-1) in addition to anthropogenic inputs. This agrees with similar results from North American boreal catchments. The slope of the linear regressions was 0.25 for both N deposition inputs (NOy and NOy + NHx), suggesting that on average, 25% of the anthropogenic N inputs is exported by rivers to the Baltic Sea. Agricultural catchments in central and southern Sweden have increased their riverine N export up to tenfold compared to the inferred background flux. Although the relatively unperturbed northernmost catchments receive significant N loads from atmospheric deposition, these catchments do not show significantly elevated riverine N export. The fact that nitrogen export in Swedish catchments appears to be higher in proportion to NANI at higher loads suggests that N retention may be saturating as loading rates increase. In northern and western Sweden the export of nitrogen is largely controlled by the hydraulic load, i.e., the riverine discharge normalized by water surface area, which has units of distance time(-1). Besides hydraulic load the percent total forest cover also affects the nitrogen export primarily in the northern and western catchments.

  • 23.
    Eriksson Hägg, Hanna
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Lyon, Steve W.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK). Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Wällstedt, Teresia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Claremar, Björn
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Future nutrient load scenarios for the Baltic Sea due to climate and lifestyle changes2014Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, nr 3, s. 337--351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dynamic model simulations of the future climate and projections of future lifestyles within the Baltic Sea Drainage Basin (BSDB) were considered in this study to estimate potential trends in future nutrient loads to the Baltic Sea. Total nitrogen and total phosphorus loads were estimated using a simple proxy based only on human population (to account for nutrient sources) and stream discharges (to account for nutrient transport). This population-discharge proxy provided a good estimate for nutrient loads across the seven sub-basins of the BSDB considered. All climate scenarios considered here produced increased nutrient loads to the Baltic Sea over the next 100 years. There was variation between the climate scenarios such that sub-basin and regional differences were seen in future nutrient runoff depending on the climate model and scenario considered. Regardless, the results of this study indicate that changes in lifestyle brought about through shifts in consumption and population potentially overshadow the climate effects on future nutrient runoff for the entire BSDB. Regionally, however, lifestyle changes appear relatively more important in the southern regions of the BSDB while climatic changes appear more important in the northern regions with regards to future increases in nutrient loads. From a whole-ecosystem management perspective of the BSDB, this implies that implementation of improved and targeted management practices can still bring about improved conditions in the Baltic Sea in the face of a warmer and wetter future climate

  • 24. Ferreira, Joao G.
    et al.
    Andersen, Jesper H.
    Borja, Angel
    Bricker, Suzanne B.
    Camp, Jordi
    da Silva, Margarida Cardoso
    Garces, Esther
    Heiskanen, Anna-Stiina
    Humborg, Christoph
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Ignatiades, Lydia
    Lancelot, Christiane
    Menesguen, Alain
    Tett, Paul
    Hoepffner, Nicolas
    Claussen, Ulrich
    Overview of eutrophication indicators to assess environmental status within the European Marine Strategy Framework Directive2011Ingår i: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 93, nr 2, s. 117-131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In 2009, following approval of the European Marine Strategy Framework Directive (MSFD, 2008/56/EC), the European Commission (EC) created task groups to develop guidance for eleven quality descriptors that form the basis for evaluating ecosystem function. The objective was to provide European countries with practical guidelines for implementing the MSFD, and to produce a Commission Decision that encapsulated key points of the work in a legal framework. This paper presents a review of work carried out by the eutrophication task group, and reports our main findings to the scientific community. On the basis of an operational, management-oriented definition, we discuss the main methodologies that could be used for coastal and marine eutrophication assessment. Emphasis is placed on integrated approaches that account for physico-chemical and biological components, and combine both pelagic and benthic symptoms of eutrophication, in keeping with the holistic nature of the MSFD. We highlight general features that any marine eutrophication model should possess, rather than making specific recommendations. European seas range from highly eutrophic systems such as the Baltic to nutrient-poor environments such as the Aegean Sea. From a physical perspective, marine waters range from high energy environments of the north east Atlantic to the permanent vertical stratification of the Black Sea. This review aimed to encapsulate that variability, recognizing that meaningful guidance should be flexible enough to accommodate the widely differing characteristics of European seas, and that this information is potentially relevant in marine ecosystems worldwide. Given the spatial extent of the MSFD, innovative approaches are required to allow meaningful monitoring and assessment. Consequently, substantial logistic and financial challenges will drive research in areas such as remote sensing of harmful algal blooms, in situ sensor development, and mathematical models. Our review takes into account related legislation, and in particular the EU Water Framework Directive (WFD - 2000/60/EC), which deals with river basins, including estuaries and a narrow coastal strip, in order to examine these issues within the framework of integrated coastal zone management.

  • 25.
    Folke, Carl
    et al.
    Stockholms universitet, Stockholm Resilience Centre. The Beijer Institute, Royal Swedish Academy of Sciences, Sweden.
    Jansson, Åsa
    Stockholms universitet, Stockholm Resilience Centre. The Beijer Institute, Royal Swedish Academy of Sciences, Sweden.
    Rockström, Johan
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Olsson, Per
    Stockholms universitet, Stockholm Resilience Centre.
    Crépin, Anne-Sophie
    Stockholms universitet, Stockholm Resilience Centre. The Beijer Institute, Royal Swedish Academy of Sciences, Sweden.
    Ebbesson, Jonas
    Stockholms universitet, Stockholm Resilience Centre. Stockholms universitet, Juridiska fakulteten, Juridiska institutionen, Stockholms miljörättscentrum (SMC).
    Elmqvist, Thomas
    Stockholms universitet, Stockholm Resilience Centre. Stockholms universitet, Naturvetenskapliga fakulteten, Systemekologiska institutionen.
    Galaz, Victor
    Stockholms universitet, Stockholm Resilience Centre.
    Moberg, Fredrik
    Stockholms universitet, Stockholm Resilience Centre. Albaeco, Stockholm, Sweden .
    Nilsson, Måns
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Österblom, Henrik
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Persson, Åsa
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Peterson, Garry
    Stockholms universitet, Stockholm Resilience Centre.
    Steffen, Will
    Stockholms universitet, Stockholm Resilience Centre.
    Walker, Brian
    Stockholms universitet, Stockholm Resilience Centre. The Beijer Institute, Royal Swedish Academy of Sciences, Sweden; CSIRO Sustainable Ecosystems, Canberra, ACT, Australia .
    Reconnecting to the biosphere2011Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 40, nr 7, s. 719-738Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Humanity has emerged as a major force in the operation of the biosphere, with a significant imprint on the Earth System, challenging social-ecological resilience. This new situation calls for a fundamental shift in perspectives, world views, and institutions. Human development and progress must be reconnected to the capacity of the biosphere and essential ecosystem services to be sustained. Governance challenges include a highly interconnected and faster world, cascading social-ecological interactions and planetary boundaries that create vulnerabilities but also opportunities for social-ecological change and transformation. Tipping points and thresholds highlight the importance of understanding and managing resilience. New modes of flexible governance are emerging. A central challenge is to reconnect these efforts to the changing preconditions for societal development as active stewards of the Earth System. We suggest that the Millennium Development Goals need to be reframed in such a planetary stewardship context combined with a call for a new social contract on global sustainability. The ongoing mind shift in human relations with Earth and its boundaries provides exciting opportunities for societal development in collaboration with the biosphere-a global sustainability agenda for humanity.

  • 26.
    Fransner, Filippa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Fransson, Agneta
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Gustafsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Tedesco, Letizia
    Hordoir, Robinson
    Nycander, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Remineralization rate of terrestrial DOC as inferred from CO2 supersaturated coastal watersManuskript (preprint) (Övrigt vetenskapligt)
  • 27.
    Fransner, Filippa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Fransson, Agneta
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum. University of Helsinki, Finland.
    Gustafsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Tedesco, Letizia
    Hordoir, Robinson
    Nycander, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Remineralization rate of terrestrial DOC as inferred from CO2 supersaturated coastal waters2019Ingår i: Biogeosciences Discussions, ISSN 1810-6277, E-ISSN 1810-6285, Vol. 16, nr 3, s. 863-879Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coastal seas receive large amounts of terrestrially derived organic carbon (OC). The fate of this carbon, and its impact on the marine environment, is however poorly understood. Here we combine underway CO2 partial pressure (pCO2) measurements with coupled 3D hydrodynamical-biogeochemical modelling to investigate whether remineralization of terrestrial dissolved organic carbon (tDOC) can explain CO2 supersaturated surface waters in the Gulf of Bothnia, a subarctic estuary. We find that a substantial remineralization of tDOC, and that a strong tDOC induced light attenuation dampening the primary production, is required to reproduce the observed CO2 supersaturated waters in the nearshore areas. A removal rate of tDOC of the order of one year, estimated in a previous modelling study in the same area, gives a good agreement between modelled and observed pCO2. The remineralization rate is on the same order as bacterial degradation rates calculated from published incubation experiments, suggesting that this remineralization could be caused by bacterial degradation. Furthermore, the observed high pCO2 values during the ice covered season argues against photochemical degradation as the main removal mechanism. All of the remineralized tDOC is outgassed to the atmosphere in the model, turning the northernmost part of the Gulf of Bothnia to a source of atmospheric CO2.

  • 28.
    Fransner, Filippa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Gustafsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Tedesco, Letizia
    Vichi, Marcello
    Hordoir, Robinson
    Roquet, Fabien
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Spilling, Kristian
    Kuznetsov, Ivan
    Eilola, Kari
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. University of Helsinki, Finland.
    Nycander, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Non-Redfieldian Dynamics Explain Seasonal pCO2 Drawdown in the Gulf of Bothnia2018Ingår i: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 123, nr 1, s. 166-188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High inputs of nutrients and organic matter make coastal seas places of intense air‐sea CO2 exchange. Due to their complexity, the role of coastal seas in the global air‐sea CO2 exchange is, however, still uncertain. Here, we investigate the role of phytoplankton stoichiometric flexibility and extracellular DOC production for the seasonal nutrient and CO2 partial pressure (pCO2) dynamics in the Gulf of Bothnia, Northern Baltic Sea. A 3‐D ocean biogeochemical‐physical model with variable phytoplankton stoichiometry is for the first time implemented in the area and validated against observations. By simulating non‐Redfieldian internal phytoplankton stoichiometry, and a relatively large production of extracellular dissolved organic carbon (DOC), the model adequately reproduces observed seasonal cycles in macronutrients and pCO2. The uptake of atmospheric CO2 is underestimated by 50% if instead using the Redfield ratio to determine the carbon assimilation, as in other Baltic Sea models currently in use. The model further suggests, based on the observed drawdown of pCO2, that observational estimates of organic carbon production in the Gulf of Bothnia, derived with the method, may be heavily underestimated. We conclude that stoichiometric variability and uncoupling of carbon and nutrient assimilation have to be considered in order to better understand the carbon cycle in coastal seas.

  • 29.
    Fransner, Filippa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Nycander, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Meier, H. E. Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU). Swedish Meteorological and Hydrological Institute, Sweden.
    Hordoir, Robinson
    Gustafsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Deutsch, Barbara
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Tracing terrestrial DOC in the Baltic Sea - a 3-D model study2016Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 30, nr 2, s. 134-148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fate of terrestrial organic matter brought to the coastal seas by rivers, and its role in the global carbon cycle, are still not very well known. Here the degradation rate of terrestrial dissolved organic carbon (DOCter) is studied in the Baltic Sea, a subarctic semi-enclosed sea, by releasing it as a tracer in a 3-D circulation model and applying linear decay constants. A good agreement with available observational data is obtained by parameterizing the degradation in two rather different ways; one by applying a decay time on the order of 10 years to the whole pool of DOCter, and one by dividing the DOCter into one refractory pool and one pool subject to a decay time on the order of 1 year. The choice of parameterization has a significant effect on where in the Baltic Sea the removal takes place, which can be of importance when modeling the full carbon cycle and the CO2 exchange with the atmosphere. In both cases the biogeochemical decay operates on time scales less than the water residence time. Therefore only a minor fraction of the DOCter reaches the North Sea, whereas approximately 80% is removed by internal sinks within the Baltic Sea. This further implies that DOCter mineralization is an important link in land-sea-atmosphere cycling of carbon in coastal- and shelf seas that are heavily influenced by riverine DOC.

  • 30. Fripiat, F.
    et al.
    Declercq, M.
    Sapart, C. J.
    Anderson, L. G.
    Brüchert, Volker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Deman, F.
    Fonseca-Batista, D.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Roukaerts, A.
    Semiletov, I. P.
    Dehairs, F.
    Influence of the bordering shelves on nutrient distribution in the Arctic halocline inferred from water column nitrate isotopes2018Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, nr 5, s. 2154-2170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The East Siberian Sea and contiguous western Arctic Ocean basin are characterized by a subsurface nutrient maximum in the halocline, generally attributed to both Pacific inflow and intensive remineralization in shelf bottom waters that are advected into the central basin. We report nitrogen and oxygen isotopic measurement of nitrate from the East Siberian Sea and western Eurasian Basin, in order to gain insight into how nitrate is processed by the microbial community and redistributed in the Arctic Ocean. A large decoupling between nitrate delta N-15 and delta O-18 is reported, increasing and decreasing upward from the Atlantic temperature maximum layer toward the surface, respectively. A correlation between water and nitrate delta O-18 indicates that most of the nitrate (> 60%) at the halocline has been regenerated within the Arctic Ocean. The increase in nitrate delta N-15 correlates with the fixed N deficit, indicating a causal link between the loss of fixed N and the delta N-15 enrichment. This suggests that a significant share of benthic denitrification is driven by nitrate supplied by remineralization and partial nitrification, allowing residual delta N-15-enriched ammonium to diffuse out of the sediments. By increasing nutrient concentrations and fixed N deficit in shelf bottom waters, this imprint is attenuated offshore following advection into the halocline by nitrate regeneration and mixing. Estimation of the sedimentary isotope effect related to benthic denitrification yields values in the range of 2.4-3.8 parts per thousand, with its magnitude driven by both the degree of coupling between remineralization and nitrification, and fixed N concentrations in shelf bottom waters.

  • 31. Gren, Ing-Marie
    et al.
    Savchuck, Oleg P.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Jansson, Torbjörn
    Cost-Effective Spatial and Dynamic Management of a Eutrophied Baltic Sea2013Ingår i: Marine Resource Economics, ISSN 0738-1360, Vol. 28, nr 3, s. 263-284Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this article is to calculate cost-effective spatial and dynamic allocations of nutrient abatement for reaching targets in a large sea with different and interlinked marine basins. A discrete dynamic model was constructed to account for measures affecting both nitrogen and phosphorus and heterogeneous and coupled marine basins within the sea. Theoretical results revealed that positive decay rates of nutrient pools in the marine basins reduce abatement costs by delaying abatement over time. The results also showed that simultaneous management of both nutrients reduces overall abatement costs as compared with separate management. An empirical application to the intergovernmental agreement on nutrient pool targets in the Baltic Sea was made by combining results from an oceanographic model with an economic model of abatement costs. The results indicate that modest changes in decay rates make a significant impact on abatement costs and that simultaneous implementation of targets for both nutrients can reduce total cost by approximately 15% compared with separate treatment. A robust result is the finding that one country, Poland, faces much higher abatement costs than the other eight riparian countries because of its relatively large discharges into a marine basin with a stringent phosphorus target and slow response to load changes.

  • 32.
    Gustafsson, Bo G.
    et al.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Rodriguez Medina, Miguel
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Validation data set compiled from Baltic Environmental Database - Version 22011Rapport (Övrig (populärvetenskap, debatt, mm))
  • 33.
    Gustafsson, Bo G.
    et al.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Schenk, Frederik
    Blenckner, Thorsten
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Eilola, Kari
    Meier, H. E. Markus
    Muller-Karulis, Barbel
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Neumann, Thomas
    Ruoho-Airola, Tuija
    Savchuk, Oleg P.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Zorita, Eduardo
    Reconstructing the Development of Baltic Sea Eutrophication 1850-20062012Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, nr 6, s. 534-548Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A comprehensive reconstruction of the Baltic Sea state from 1850 to 2006 is presented: driving forces are reconstructed and the evolution of the hydrography and biogeochemical cycles is simulated using the model BALTSEM. Driven by high resolution atmospheric forcing fields (HiResAFF), BALTSEM reproduces dynamics of salinity, temperature, and maximum ice extent. Nutrient loads have been increasing with a noteworthy acceleration from the 1950s until peak values around 1980 followed by a decrease continuing up to present. BALTSEM shows a delayed response to the massive load increase with most eutrophic conditions occurring only at the end of the simulation. This is accompanied by an intensification of the pelagic cycling driven by a shift from spring to summer primary production. The simulation indicates that no improvement in water quality of the Baltic Sea compared to its present state can be expected from the decrease in nutrient loads in recent decades.

  • 34.
    Gustafsson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Deutsch, Barbara
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Carbon cycling in the Baltic Sea - The fate of allochthonous organic carbon and its impact on air-sea CO2 exchange2014Ingår i: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 129, s. 289-302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A coupled physical-biogeochemical model (BALTSEM) is used to estimate carbon fluxes in the Baltic Sea over the 1980-2006 period. Budget calculations for organic carbon indicate that of the total allochthonous organic carbon (TOCT) supplied to the system, on average 56% is mineralized, 36% is exported out of the system, and the remainder is buried. River discharge is the main source of dissolved inorganic carbon (DIC) to the Baltic Sea. However, model results indicate that in the Gulf of Bothnia (northern Baltic Sea), the contribution to the DIC stock by TOCT mineralization is of the same order as direct river input of DIC In the Kattegat and Danish Straits (southwestern Baltic Sea) on the other hand, net uptake of atmospheric CO2 comprises the major DIC source. Despite large variations within the system, with net outgassing from some sub-basins and net absorption in others, the Baltic Sea as a whole was estimated to be a net sink for atmospheric CO2. Mineralization of allochthonous dissolved organic carbon (DOCT) influences air-sea CO2 exchange. A sensitivity study indicates that depending on the labile fraction of DOCT, the contribution from CO2 absorption to total external DIC sources can amount to 10-25%.

  • 35.
    Gustafsson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Hagens, Mathilde
    Sun, Xiaole
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum.
    Reed, Daniel C.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi. University of Helsinki, Finland.
    Slomp, Caroline P.
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. University of Helsinki, Finland.
    Sedimentary alkalinity generation and long-term alkalinity development in the Baltic Sea2019Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 16, nr 2, s. 437-456Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Enhanced release of alkalinity from the seafloor, principally driven by anaerobic degradation of organic matter under low-oxygen conditions and associated secondary redox reactions, can increase the carbon dioxide (CO2) buffering capacity of seawater and therefore oceanic CO2 uptake. The Baltic Sea has undergone severe changes in oxygenation state and total alkalinity (TA) over the past decades. The link between these concurrent changes has not yet been investigated in detail. A recent system-wide TA budget constructed for the past 50 years using BALTSEM, a coupled physical-biogeochemical model for the whole Baltic Sea area, revealed an unknown TA source. Here we use BALTSEM in combination with observational data and one-dimensional reactive transport modelling of sedimentary processes in the Fårö Deep, a deep Baltic Sea basin, to test whether sulfate reduction coupled to iron (Fe) sulfide burial can explain the missing TA source in the Baltic Proper. We calculated that this burial can account for 26% of the missing source in this basin, with the remaining TA possibly originating from unknown river inputs or submarine groundwater discharge. We also show that temporal variability in the input of Fe to the sediments since the 1970s drives changes in sulfur burial in the Fårö Deep, suggesting that Fe availability is the ultimate limiting factor for TA generation under anoxic conditions. The implementation of projected climate change and two nutrient load scenarios for the 21st century in BALTSEM shows that reducing nutrient loads will improve deep water oxygen conditions, but at the expense of lower surface water TA concentrations, CO2 buffering capacities and faster acidification. When these changes additionally lead to a decrease in Fe inputs to the sediment of the deep basins, anaerobic TA generation will be reduced even further, thus exacerbating acidification. This work highlights that Fe dynamics play a key role in the release of TA from sediments where Fe sulfide formation is limited by Fe availability, as exemplified for the Baltic Sea. Moreover, it demonstrates that burial of Fe sulfides should be included in TA budgets of low oxygen basins.

  • 36.
    Gustafsson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Björk, Göran
    Stranne, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. University of New Hampshire, USA.
    Andersson, Leif G.
    Geibel, Marc C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Sundbom, Marcus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Semiletov, Igor P.
    Thornton, Brett F.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Carbon cycling on the East Siberian Arctic Shelf – a change in air-sea CO2 flux induced by mineralization of terrestrial organic carbon2017Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measurements from the SWERUS-C3 and ISSS-08 Arctic expeditions were used to calibrate and validate a new physical-biogeochemical model developed to quantify key carbon cycling processes on the East Siberian Arctic Shelf (ESAS). The model was used in a series of experimental simulations with the specific aim to investigate the pathways of terrestrial dissolved and particulate organic carbon (DOCter and POCter) supplied to the shelf. Rivers supply on average 8.5 Tg C yr−1 dissolved inorganic carbon (DIC), and further 8.5 and 1.1 Tg C yr−1 DOCter and POCter respectively. Based on observed and simulated DOC concentrations and stable isotope values (δ13CDOC) in shelf waters, we estimate that only some 20 % of the riverine DOCter is labile. According to our model results, an additional supply of approximately 14 Tg C yr−1 eroded labile POCter is however required to describe the observed stable isotope values of DIC (δ13CDIC). Degradation of riverine DOCter and POCter results in a 1.8 Tg C yr−1 reduction in the uptake of atmospheric CO2, while degradation of eroded POCter results in an additional 10 Tg C yr−1 reduction. Our calculations indicate nevertheless that the ESAS is an overall small net sink for atmospheric CO2 (1.7 Tg C yr−1). The external carbon sources are largely compensated by a net export from the shelf to the Arctic Ocean (31 Tg C yr−1), and to a smaller degree by a permanent burial in the sediments (2.7 Tg C yr−1).

  • 37.
    Gustafsson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Modelling the C-13 and C-12 isotopes of inorganic and organic carbon in the Baltic Sea2015Ingår i: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 148, s. 122-130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, C-12 and C-13 contents of all carbon containing state variables (dissolved inorganic and organic carbon, detrital carbon, and the carbon content of autotrophs and heterotrophs) have for the first time been explicitly included in a coupled physical-biogeochemical Baltic Sea model. Different processes in the carbon cycling have distinct fractionation values, resulting in specific isotopic fingerprints. Thus, in addition to simulating concentrations of different tracers, our new model formulation improves the possibility to constrain the rates of processes such as CO2 assimilation, mineralization, and air-sea exchange. We demonstrate that phytoplankton production and respiration, and the related air-sea CO2 fluxes, are to a large degree controlling the isotopic composition of organic and inorganic carbon in the system. The isotopic composition is further, but to a lesser extent, influenced by river loads and deep water inflows as well as transformation of terrestrial organic carbon within the system. Changes in the isotopic composition over the 20th century have been dominated by two processes the preferential release of C-12 to the atmosphere in association with fossil fuel burning, and the eutrophication of the Baltic Sea related to increased nutrient loads under the second half of the century.

  • 38.
    Gustafsson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Omstedt, Anders
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    The air-water CO2 exchange of a coastal sea – a sensitivity study on factors that influence the absorption and outgassing of CO2 in the Baltic Sea2015Ingår i: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 120, nr 8, s. 5342-5357Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, the BALTSEM model is used to estimate how air-water CO2 fluxes in the Baltic Sea respond to parameterizations of organic alkalinity (Aorg), gas transfer, and phytoplankton growth, and further to changes in river loads. The forcing data include the most complete compilation of Baltic river loads for dissolved inorganic and organic carbon (DIC and DOC) and total alkalinity (TA). In addition, we apply the most recent estimates of internal TA generation in the system. Our results clearly demonstrate how air-water CO2 fluxes of a coastal sea depend on river loads of carbon, TA, and nutrients as well the freshwater import itself. Long-term changes in DIC loads are shown to be compensated by corresponding changes in air-water CO2 exchange. By adding Aorg, a discrepancy in the carbonate system calculations was removed, and the simulated net CO2 absorption of the system decreased by 11%. A new parameterization for cyanobacteria growth significantly improved the seasonal development of pCO2 in the central Baltic Sea, although the net effect on CO2 fluxes was below 5%. By applying either a linear, quadratic, or cubic wind speed dependence for gas transfer, the long-term net CO2 exchange was adjusted by less than 5%. There is no clear indication that any one of these parameterizations provides a more accurate estimate of CO2 fluxes than the other two. Our findings are applicable in other coastal areas that are heavily influenced by river loads of TA, DIC, and DOC.

  • 39.
    Gustafsson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Wällstedt, Teresia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    External total alkalinity loads versus internal generation: The influence of nonriverine alkalinity sources in the Baltic Sea2014Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 28, nr 11, s. 1358-1370Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study we first present updated riverine total alkalinity (TA) loads to the various Baltic Sea sub-basins, based on monthly measurements in 82 of the major rivers that represent 85% of the total runoff. Simulations in the coupled physical-biogeochemical BALTSEM (BAltic sea Long-Term large Scale Eutrophication Model) model show that these river loads together with North Sea water inflows are not sufficient to reproduce observed TA concentrations in the system, demonstrating the large influence from internal sources. Budget calculations indicate that the required internal TA generation must be similar to river loads in magnitude. The nonriverine source in the system amounts to about 2.4mmolm(-2) d(-1) on average. We argue here that the majority of this source is related to denitrification together with unresolved sediment processes such as burial of reduced sulfur and/or silicate weathering. This hypothesis is supported by studies on sediment processes on a global scale and also by data from sediment cores in the Baltic Sea. In a model simulation with all internal TA sources and sinks switched on, the net absorption of atmospheric CO2 increased by 0.78mol C m(-2) yr(-1) compared to a simulation where TA was treated as a passive tracer. Our results clearly illustrate how pelagic TA sources together with anaerobic mineralization in coastal sediments generate a significant carbon sink along the aquatic continuum, mitigating CO2 evasions from coastal and estuarine systems.

  • 40. Gårdmark, Anna
    et al.
    Lindegren, Martin
    Neuenfeldt, Stefan
    Blenckner, Thorsten
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre, Baltic Nest Institute.
    Heikinheimo, Outi
    Müller-Karulis, Barbel
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre, Baltic Nest Institute. Institute of Food Safety, Animal Health and Environment BIOR, Latvia.
    Niiranen, Susa
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre, Baltic Nest Institute.
    Tomczak, Maciej T.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre, Baltic Nest Institute.
    Aro, Eero
    Wikström, Anders
    Moellmann, Christian
    Biological ensemble modeling to evaluate potential futures of living marine resources2013Ingår i: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 23, nr 4, s. 742-754Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 41. Hermans, Martijn
    et al.
    K. Lenstra, Wytze
    van Helmond, Niels A. G. M.
    Behrends, Thilo
    Egger, Matthias
    Séguret, Marie J. M.
    Gustafsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. University of Helsinki, Finland.
    Slomp, Caroline P.
    Impact of natural re-oxygenation on the sediment dynamics of manganese, iron and phosphorus in a euxinic Baltic Sea basin2019Ingår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 246, s. 174-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Baltic Sea is characterized by the largest area of hypoxic (oxygen (O2) < 2 mg L−1) bottom waters in the world’s ocean induced by human activities. Natural ventilation of these O2-depleted waters largely depends on episodic Major Baltic Inflows from the adjacent North Sea. In 2014 and 2015, two such inflows led to a strong rise in O2 and decline in phosphate (HPO42−) in waters below 125 m depth in the Eastern Gotland Basin. This provided the opportunity to assess the impact of such re-oxygenation events on the cycles of manganese (Mn), iron (Fe) and phosphorus (P) in the sediment for the first time. We demonstrate that the re-oxygenation induced the activity of sulphur (S)-oxidising bacteria, known as Beggiatoaceae in the surface sediment where a thin oxic and suboxic layer developed. At the two deepest sites, strong enrichments of total Mn and to a lesser extent Fe oxides and P were observed in this surface layer. A combination of sequential sediment extractions and synchrotron-based X-ray spectroscopy revealed evidence for the abundant presence of P-bearing rhodochrosite and Mn(II) phosphates. In contrast to what is typically assumed, the formation of Fe oxides in the surface sediment was limited. We attribute this lack of Fe oxide formation to the high flux of reductants, such as sulphide, from deeper sediments which allows Fe(II) in the form of FeS to be preserved and restricts the penetration of O2 into the sediment. We estimate that enhanced P sequestration in surface sediments accounts for only ∼5% of water column HPO42− removal in the Eastern Gotland Basin linked to the recent inflows. The remaining HPO42− was transported to adjacent areas in the Baltic Sea. Our results highlight that the benthic O2 demand arising from the accumulation of organic-rich sediments over several decades, the legacy of hypoxia, has major implications for the biogeochemical response of euxinic basins to re-oxygenation. In particular, P sequestration in the sediment in association with Fe oxides is limited. This implies that artificial ventilation projects that aim at removing water column HPO42− and thereby improving water quality in the Baltic Sea will likely not have the desired effect.

  • 42. Hong, Bongghi
    et al.
    Swaney, Dennis P.
    Mörth, Carl-Magnus
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Smedberg, Erik
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Hägg, Hanna Eriksson
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Humborg, Christoph
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Howarth, Robert W.
    Bouraoui, Faycal
    Evaluating regional variation of net anthropogenic nitrogen and phosphorus inputs (NANI/NAPI), major drivers, nutrient retention pattern and management implications in the multinational areas of Baltic Sea basin2012Ingår i: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 227, s. 117-135Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The NANI/NAPI (net anthropogenic nitrogen/phosphorus input) Calculator Toolbox described in this paper is designed to address the consequences to Baltic Sea nutrient loads of the significant variation in agronomic practices and dietary preferences among European countries whose watersheds comprise the Baltic Sea basin. A primary objective of this work is to develop regional parameters and datasets for this budgeting tool. A previous version of the toolbox was applied to the entire contiguous United States to calculate NANI and its components (atmospheric N deposition, fertilizer N application, agricultural N fixation and N in net food and feed imports). Here, it is modified for application to the Baltic Sea catchments, where coastal watersheds from several countries are draining to international waters. A similar accounting approach is taken for calculating NAPI, which includes fertilizer P application, P in net food and feed imports and non-food use of P by human. Regional variation of NANI/NAPI parameters (agricultural fixation rates, human intake rates and livestock intake and excretion rates) are estimated, and their impact on the regional nutrient budget and the riverine nutrient flux is evaluated. There is a distinct north-to-south gradient in NANI and NAPI across the Baltic Sea catchments, and regional nutrient inputs are strongly related to riverine nutrient fluxes. Analysis of regional nutrient retention pattern indicates that, for some countries, compliance to the Baltic Sea Action Plan would imply enormous changes in the agricultural sector.

  • 43.
    Humborg, Christoph
    et al.
    Stockholms universitet, Stockholm Resilience Centre. Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Österblom, Henrik
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Modeller för Östersjöns hälsa2009Ingår i: Miljöforskning, nr 3/4Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 44.
    Humborg, Cristoph
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Mörth, Carl Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Sundbom, Marcus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Borg, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Blenckner, Thorsten
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Giesler, R.
    Ittekkot, V.
    CO2 supersaturation along the aquatic conduit in Swedish watersheds as constrained by terrestrial respiration, aquatic respiration and weathering2010Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 6, nr 7, s. 1966-1978Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We tested the hypothesis that CO2 supersaturation along the aquatic conduit over Sweden can be explained by processes other than aquatic respiration. A first generalized-additive model (GAM) analysis evaluating the relationships between single water chemistry variables and pCO(2) in lakes and streams revealed that water chemistry variables typical for groundwater input, e.g., dissolved silicate (DSi) and Mg2+ had explanatory power similar to total organic carbon (TOC). Further GAM analyses on various lake size classes and stream orders corroborated the slightly higher explanatory power for DSi in lakes and Mg2+ for streams compared with TOC. Both DSi and TOC explained 22-46% of the pCO(2) variability in various lake classes (0.01-> 100 km2) and Mg2+ and TOC explained 11-41% of the pCO(2) variability in the various stream orders. This suggests that aquatic pCO(2) has a strong groundwater signature. Terrestrial respiration is a significant source of the observed supersaturation and we may assume that both terrestrial respiration and aquatic respiration contributed equally to pCO(2) efflux. pCO(2) and TOC concentrations decreased with lake size suggesting that the longer water residence time allow greater equilibration of CO2 with the atmosphere and in-lake mineralization of TOC. For streams, we observed a decreasing trend in pCO(2) with stream orders between 3 and 6. We calculated the total CO2 efflux from all Swedish lakes and streams to be 2.58 Tg C yr-1. Our analyses also demonstrated that 0.70 Tg C yr-1 are exported to the ocean by Swedish watersheds as HCO3- and CO(3)2- of which about 0.56 Tg C yr-1 is also a residual from terrestrial respiration and constitute a long-term sink for atmospheric CO2. Taking all dissolved inorganic carbon (DIC) fluxes along the aquatic conduit into account will lower the estimated net ecosystem C exchange (NEE) by 2.02 Tg C yr-1, which corresponds to 10% of the NEE in Sweden.

  • 45. Isaev, A. V.
    et al.
    Eremina, T. R.
    Ryabchenko, V. A.
    Savchuk, Oleg P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute. St. Petersburg State University, Russia.
    Model estimates of the impact of bioirrigation activity of Marenzelleria spp. on the Gulf of Finland ecosystem in a changing climate2017Ingår i: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 171, s. 81-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Drastic changes have occurred in the Eastern Gulf of Finland ecosystem after recent invasion and establishment of polychaete Marenzelleria spp. Possible mechanisms of these changes are explored with the help of three-dimensional ecosystem model SPBEM. Relative significance of bioirrigation activity is studied by comparison of two climate change scenario simulations, which include or disregard Marenzelleria effects. The novel results obtained with this approach demonstrate that on a system level biogeochemical consequences of both implemented climate changes scenario and polychaete activity are equivalent to a weakening of vicious circle of the Baltic Sea eutrophication. The eutrophication-mitigating effects of the Marenzelleria invasion into the Eastern Gulf of Finland, revealed by the long-term field measurements, are explained by simulation-based considerations.

  • 46.
    Jilbert, T.
    et al.
    Department of Earth Sciences (Geochemistry), Faculty of Geosciences, Utrecht University.
    Slomp, C. P.
    Department of Earth Sciences (Geochemistry), Faculty of Geosciences, Utrecht University.
    Gustafsson, Bo G.
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Boer, W.
    Royal Netherlands Institute for Sea Research.
    Beyond the Fe-P-redox connection: preferential regeneration of phosphorus from organic matter as a key control on Baltic Sea nutrient cycles2011Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 8, s. 1699-1720Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Patterns of regeneration and burial of phosphorus (P) in the Baltic Sea are strongly dependent on redox conditions. Redox varies spatially along water depth gradients and temporally in response to the seasonal cycle and multidecadal hydrographic variability. Alongside the well-documented link between iron oxyhydroxide dissolution and release of P from Baltic Sea sediments, we show that preferential remineralization of P with respect to carbon (C) and nitrogen (N) during degradation of organic matter plays a key role in determining the surplus of bioavailable P in the water column. Preferential remineralization of P takes place both in the water column and upper sediments and its rate is shown to be redox-dependent, increasing as reducing conditions become more severe at greater water-depth in the deep basins. Existing Redfield-based biogeochemical models of the Baltic may therefore underestimate the imbalance between N and P availability for primary production, and hence the vulnerability of the Baltic to sustained eutrophication via the fixation of atmospheric N. However, burial of organic P is also shown to increase during multidecadal intervals of expanded hypoxia, due to higher net burial rates of organic matter around the margins of the deep basins. Such intervals may be characterized by basin-scale acceleration of all fluxes within the P cycle, including productivity, regeneration and burial, sustained by the relative accessibility of the water column P pool beneath a shallow halocline.

  • 47. Jilbert, Tom
    et al.
    Conley, Daniel J.
    Gustafsson, Bo G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Funkey, Carolina P.
    Slomp, Caroline P.
    Glacio-isostatic control on hypoxia in a high-latitude shelf basin2015Ingår i: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 43, nr 5, s. 427-430Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In high-latitude continental shelf environments, late Pleistocene glacial overdeepening and early Holocene eustatic sea-level rise combined to create restricted marine basins with a high vulnerability to oxygen depletion. Here we show that ongoing glacio-isostatic rebound during the Holocene may have played an important role in determining the distribution of past hypoxia in these environments by controlling the physical exchange of water masses and the distribution of large-scale phosphorus (P) sinks. We focus on the Baltic Sea, where sediment records from a large, presently oxic sub-basin show evidence for intense hypoxia and cyanobacteria blooms during the Holocene Thermal Maximum. Using paleobathymetric modeling, we show that this period was characterized by enhanced deep-water exchange, allowing widespread phosphorus regeneration. Intra-basin sills then shoaled over a period of several thousand years, enhancing P burial in one of the sub-basins. Together with climate forcing, this may have caused the termination of hypoxia throughout the Baltic Sea. Similar rearrangements of physical and chemical processes likely occurred in response to glacio-isostatic rebound in other high-latitude shelf basins during the Holocene.

  • 48.
    Kadin, Martina
    et al.
    Stockholms universitet, Stockholm Resilience Centre.
    Österblom, Henrik
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Bignert, Anders
    Swedish Museum of Natural History.
    Hentati-Sundberg, Jonas
    Stockholms universitet, Stockholm Resilience Centre.
    Olsson, Olof
    Stockholms universitet, Stockholm Resilience Centre.
    Trends, changes and uncertainties in bycatch of common murres in the Baltic SeaManuskript (preprint) (Övrigt vetenskapligt)
  • 49.
    Kadin, Martina
    et al.
    Stockholms universitet, Stockholm Resilience Centre.
    Österblom, Henrik
    Stockholms universitet, Stockholm Resilience Centre, Baltic Nest Institute.
    Hentati-Sundberg, Jonas
    Stockholms universitet, Stockholm Resilience Centre.
    Olsson, Olof
    Stockholms universitet, Stockholm Resilience Centre.
    Contrasting effects of food quality and quantity on a marine top predator2012Ingår i: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 444, s. 239-249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Overfishing of predatory fish has contributed to an increase in forage-fish stocks. At the same time, a rising demand for forage fish to supply fishmeal markets, in combination with ­climate change, has put strong pressure on these stocks, and this, in turn, has had an impact on marine top predators. We examined how inter-annual variation in food quality (sprat Sprattus sprattus weight-at-age) and quantity (sprat abundance) influenced Baltic Sea common murres Uria aalge during chick-rearing. Fledging success, i.e. survival from hatching to fledging, showed a positive relationship with food quality, but we found no effect of food quantity. We found no relationship between food quality and parental behaviour or chick feeding parameters, but a negative relationship between food quantity and trip duration. Our data indicate that there was room for parental birds to increase their effort to compensate for reduced food quality, but we found no signs of such compensation. We analysed different types of fish and seabird life-history data to separate effects of food quantity and quality on a top predator. Understanding such effects can contribute to clarifying causes and consequences for observed changes in life-history parameters and population dynamics of top predators.

  • 50. Kahru, Mati
    et al.
    Elmgren, Ragnar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Di Lorenzo, Emanuele
    Savchuck, Oleg
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholms universitets Östersjöcentrum, Baltic Nest Institute.
    Unexplained interannual oscillations of cyanobacterial blooms in the Baltic Sea2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 6365Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Population oscillations in multi-species or even single species systems are well-known but have rarely been detected at the lower trophic levels in marine systems. Nitrogen fixing cyanobacteria are a major component of the Baltic Sea ecosystem and sometimes form huge surface accumulations covering most of the sea surface. By analysing a satellite-derived 39-year (1979–2017) data archive of surface cyanobacteria concentrations we have found evidence of strikingly regular interannual oscillations in cyanobacteria concentrations in the northern Baltic Sea. These oscillations have a period of ~3 years with a high-concentration year generally followed by one or two low-concentration years. Changes in abiotic factors known to influence the growth and survival of cyanobacteria could not provide an explanation for the oscillations. We therefore assume that these oscillations are intrinsic to the marine system, caused by an unknown, probably mainly biological mechanism that may be triggered by a combination of environmental factors. Interactions between different life cycle stages of cyanobacteria as well as between predator-prey or host-parasite are possible candidates for causing the oscillations.

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