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  • 1. Gren, Ing-Marie
    et al.
    Savchuck, Oleg P.
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Jansson, Torbjörn
    Cost-Effective Spatial and Dynamic Management of a Eutrophied Baltic Sea2013In: Marine Resource Economics, ISSN 0738-1360, Vol. 28, no 3, p. 263-284Article in journal (Refereed)
    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.

  • 2.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Müller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Key processes in the coupled carbon, nitrogen, and phosphorus cycling of the Baltic Sea2017In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 134, no 3, p. 301-317Article in journal (Refereed)
    Abstract [en]

    In this study we examine pools of carbon (C), nitrogen (N), and phosphorus (P) in the Baltic Sea, both simulated and reconstructed from observations. We further quantify key fluxes in the C, N, and P cycling. Our calculations include pelagic reservoirs as well as the storage in the active sediment layer, which allows a complete coverage of the overall C, N, and P cycling on a system-scale. A striking property of C versus N and P cycling is that while the external supplies of total N and P (TN and TP) are largely balanced by internal removal processes, the total carbon (TC) supply is mainly compensated by a net export out of the system. In other words, external inputs of TN and TP are, in contrast to TC, rather efficiently filtered within the Baltic Sea. Further, there is a net export of TN and TP out of the system, but a net import of dissolved inorganic N and P (DIN and DIP). There is on the contrary a net export of both the organic and inorganic fractions of TC. While the pelagic pools of TC and TP are dominated by inorganic compounds, TN largely consists of organic N because allochthonous organic N is poorly degradable. There are however large basin-wise differences in C, N, and P elemental ratios as well as in inorganic versus organic fractions. These differences reflect both the differing ratios in external loads and differing oxygen conditions determining the redox-dependent fluxes of DIN and DIP.

  • 3. Isaev, A. V.
    et al.
    Eremina, T. R.
    Ryabchenko, V. A.
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, 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 climate2017In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 171, p. 81-88Article in journal (Refereed)
    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.

  • 4. Kahru, Mati
    et al.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Di Lorenzo, Emanuele
    Savchuck, Oleg
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Unexplained interannual oscillations of cyanobacterial blooms in the Baltic Sea2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 6365Article in journal (Refereed)
    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.

  • 5. Kahru, Mati
    et al.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Changing seasonality of the Baltic Sea2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 4, p. 1009-1018Article in journal (Refereed)
    Abstract [en]

    Changes in the phenology of physical and ecological variables associated with climate change are likely to have significant effect on many aspects of the Baltic ecosystem. We apply a set of phenological indicators to multiple environmental variables measured by satellite sensors for 17-36 years to detect possible changes in the seasonality in the Baltic Sea environment. We detect significant temporal changes, such as earlier start of the summer season and prolongation of the productive season, in several variables ranging from basic physical drivers to ecological status indicators. While increasing trends in the absolute values of variables like sea-surface temperature (SST), diffuse attenuation of light (Ked490) and satellite-detected chlorophyll concentration (CHL) are detectable, the corresponding changes in their seasonal cycles are more dramatic. For example, the cumulative sum of 30 000 W m(-2) of surface incoming short-wave irradiance (SIS) was reached 23 days earlier in 2014 compared to the beginning of the time series in 1983. The period of the year with SST of at least 17 degrees C has almost doubled (from 29 days in 1982 to 56 days in 2014), and the period with Ked490 over 0.4 m(1) has increased from about 60 days in 1998 to 240 days in 2013 -i.e., quadrupled. The period with satellite-estimated CHL of at least 3 mg m(-3) has doubled from approximately 110 days in 1998 to 220 days in 2013. While the timing of both the phytoplankton spring and summer blooms have advanced, the annual CHL maximum that in the 1980s corresponded to the spring diatom bloom in May has now shifted to the summer cyanobacteria bloom in July.

  • 6. Lehtoranta, Jouni
    et al.
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Elken, Juri
    Dahlbo, Kim
    Kuosa, Harri
    Raateoja, Mika
    Kauppila, Pirkko
    Raike, Antti
    Pitkanen, Heikki
    Atmospheric forcing controlling inter-annual nutrient dynamics in the open Gulf of Finland2017In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 171, p. 4-20Article in journal (Refereed)
    Abstract [en]

    The loading of P into the Gulf of Finland has decreased markedly, but no overall trend in the concentration of P has been observed in the open Gulf, where the concentrations of both inorganic N and P still have a pronounced inter annual variability. Our main aim was to study whether the internal processes driven by atmospheric forcing can explain the variation in the nutrient conditions in the Gulf during the period 1992-2014. We observed that the long-term salinity variation of the bottom water in the northern Baltic Proper controls that in the Gulf, and that the deep-water concentrations of oxygen and nutrients are significantly correlated between the basins. This imposes preconditions regarding how atmospheric forcing may influence deep water flows and stratification in the Gulf on a long-term scale. We found that over short timescales, winter winds in particular can control the in- and outflows of water and the vertical stratification and mixing, which to a large extent explained the inter-annual variation in the DIN and TP pools in the Gulf. We conclude that the inter-annual variation in the amounts, ratios, and spatial distribution of nutrients sets variable preconditions for the spring and potential blue-green algae blooms, and that internal processes were able to mask the effects of the P load reductions implemented across the whole Gulf. The transportation of P along the bottom from the northern Baltic Proper and its evident uplift in the Gulf highlights the fact that the nutrient reductions are also needed in the entire catchment of the Baltic Sea to improve the trophic status of the open Gulf.

  • 7.
    McCrackin, Michelle L.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Hong, Bongghi
    Howarth, Robert W.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Svanbäck, Annika
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Swaney, Dennis P.
    Opportunities to reduce nutrient inputs to the Baltic Sea by improving manure use efficiency in agriculture2018In: Regional Environmental Change, ISSN 1436-3798, E-ISSN 1436-378X, Vol. 18, no 6, p. 1843-1854Article in journal (Refereed)
    Abstract [en]

    While progress has been made in reducing external nutrient inputs to the Baltic Sea, further actions are needed to meet the goals of the Baltic Sea Action Plan (BSAP), especially for the Baltic Proper, Gulf of Finland, and Gulf of Riga sub-basins. We used the net anthropogenic nitrogen and phosphorus inputs (NANI and NAPI, respectively) nutrient accounting approach to construct three scenarios of reduced NANI-NAPI. Reductions assumed that manure nutrients were redistributed from areas with intense animal production to areas that focus on crop production and would otherwise import synthetic and mineral fertilizers. We also used the Simple as Necessary Baltic Long Term Large Scale (SANBALTS) model to compare eutrophication conditions for the scenarios to current and BSAP-target conditions. The scenarios suggest that reducing NANI-NAPI by redistributing manure nutrients, together with improving agronomic practices, could meet 54–82% of the N reductions targets (28–43 kt N reduction) and 38–64% P reduction targets (4–6.6 kt P reduction), depending on scenario. SANBALTS output showed that even partial fulfillment of nutrient reduction targets could have ameliorating effects on eutrophication conditions. Meeting BSAP targets will require addressing additional sources, such as sewage. A common approach to apportioning sources to external nutrients loads could enable further assessment of the feasibility of eutrophication management targets.

  • 8. Meier, H. E. Markus
    et al.
    Andersson, Helen C.
    Arheimer, Berit
    Donnelly, Chantal
    Eilola, Kari
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Kotwicki, Lech
    Neset, Tina-Simone
    Niiranen, Susa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Piwowarczyk, Joanna
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Schenk, Frederik
    Weslawski, Jan Marcin
    Zorita, Eduardo
    Ensemble Modeling of the Baltic Sea Ecosystem to Provide Scenarios for Management2014In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, no 1, p. 37-48Article in journal (Refereed)
    Abstract [en]

    We present a multi-model ensemble study for the Baltic Sea, and investigate the combined impact of changing climate, external nutrient supply, and fisheries on the marine ecosystem. The applied regional climate system model contains state-of-the-art component models for the atmosphere, sea ice, ocean, land surface, terrestrial and marine biogeochemistry, and marine food-web. Time-dependent scenario simulations for the period 1960-2100 are performed and uncertainties of future projections are estimated. In addition, reconstructions since 1850 are carried out to evaluate the models sensitivity to external stressors on long time scales. Information from scenario simulations are used to support decision-makers and stakeholders and to raise awareness of climate change, environmental problems, and possible abatement strategies among the general public using geovisualization. It is concluded that the study results are relevant for the Baltic Sea Action Plan of the Helsinki Commission.

  • 9. Meier, H. E. Markus
    et al.
    Edman, Moa
    Eilola, Kari
    Placke, Manja
    Neumann, Thomas
    Andersson, Helen C.
    Brunnabend, Sandra-Esther
    Dieterich, Christian
    Frauen, Claudia
    Friedland, Rene
    Gröger, Matthias
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Gustafsson, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Isaev, Alexey
    Kniebusch, Madline
    Kuznetsov, Ivan
    Müller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Naumann, Michael
    Omstedt, Anders
    Ryabchenko, Vladimir
    Saraiva, Sofia
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Assessment of Uncertainties in Scenario Simulations of Biogeochemical Cycles in the Baltic Sea2019In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 6, article id 46Article, review/survey (Refereed)
    Abstract [en]

    Following earlier regional assessment studies, such as the Assessment of Climate Change for the Baltic Sea Basin and the North Sea Region Climate Change Assessment, knowledge acquired from available literature about future scenario simulations of biogeochemical cycles in the Baltic Sea and their uncertainties is assessed. The identification and reduction of uncertainties of scenario simulations are issues for marine management. For instance, it is important to know whether nutrient load abatement will meet its objectives of restored water quality status in future climate or whether additional measures are required. However, uncertainties are large and their sources need to be understood to draw conclusions about the effectiveness of measures. The assessment of sources of uncertainties in projections of biogeochemical cycles based on authors' own expert judgment suggests that the biggest uncertainties are caused by (1) unknown current and future bioavailable nutrient loads from land and atmosphere, (2) the experimental setup (including the spin up strategy), (3) differences between the projections of global and regional climate models, in particular, with respect to the global mean sea level rise and regional water cycle, (4) differing model-specific responses of the simulated biogeochemical cycles to long-term changes in external nutrient loads and climate of the Baltic Sea region, and (5) unknown future greenhouse gas emissions. Regular assessments of the models' skill (or quality compared to observations) for the Baltic Sea region and the spread in scenario simulations (differences among projected changes) as well as improvement of dynamical downscaling methods are recommended.

  • 10. Meier, H. E. Markus
    et al.
    Edman, Moa K.
    Eilola, Kari J.
    Placke, Manja
    Neumann, Thomas
    Andersson, Helén C.
    Brunnabend, Sandra-Esther
    Dieterich, Christian
    Frauen, Claudia
    Friedland, René
    Gröger, Matthias
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. University of Helsinki, Finland.
    Gustafsson, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Isaev, Alexey
    Kniebusch, Madline
    Kuznetsov, Ivan
    Müller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Omstedt, Anders
    Ryabchenko, Vladimir
    Saraiva, Sofia
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Assessment of Eutrophication Abatement Scenarios for the Baltic Sea by Multi-Model Ensemble Simulations2018In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 5, article id 440Article in journal (Refereed)
    Abstract [en]

    To assess the impact of the implementation of the Baltic Sea Action Plan (BSAP) on the future environmental status of the Baltic Sea, available uncoordinated multi-model ensemble simulations for the Baltic Sea region for the twenty-first century were analyzed. 

    The scenario simulations were driven by regionalized global general circulation model (GCM) data using several regional climate system models and forced by various future greenhouse gas emission and air- and river-borne nutrient load scenarios following either reference conditions or the BSAP. To estimate uncertainties in projections, the largest ever multi-model ensemble for the Baltic Sea comprising 58 transient simulations for the twenty-first century was assessed. Data from already existing simulations from different projects including regionalized GCM simulations of the third and fourth assessment reports of the Intergovernmental Panel on Climate Change based on the corresponding Coupled Model Intercomparison Projects, CMIP3 and CMIP5, were collected.

    Various strategies to weigh the ensemble members were tested and the results for ensemble mean changes between future and present climates are shown to be robust with respect to the chosen metric. Although (1) the model simulations during the historical period are of different quality and (2) the assumptions on nutrient load levels during present and future periods differ between models considerably, the ensemble mean changes in biogeochemical variables in the Baltic proper with respect to nutrient load reductions are similar between the entire ensemble and a subset consisting only of the most reliable simulations.

    Despite the large spread in projections, the implementation of the BSAP will lead to a significant improvement of the environmental status of the Baltic Sea according to both weighted and unweighted ensembles. The results emphasize the need for investigating ensembles with many members and rigorous assessments of models’ performance.

  • 11. Ryabchenko, V. A.
    et al.
    Karlin, L. N.
    Isaev, A. V.
    Vankevich, R. E.
    Eremina, T. R.
    Molchanov, M. S.
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. St. Petersburg State University, Russia.
    Model estimates of the eutrophication of the Baltic Sea in the contemporary and future climate2016In: Oceanology (Washington. 1965), ISSN 0001-4370, E-ISSN 0001-4370, Vol. 56, no 1, p. 36-45Article in journal (Refereed)
    Abstract [en]

    The St. Petersburg Baltic eutrophication model (SPBEM) is used to assess the ecological condition of the sea under possible changes in climate and nutrient loads in the 21st century. According to model estimates, in the future climate water quality will worsen, compared to modern conditions. This deterioration is stronger in the climate warming scenario with a stronger change in future near-surface air temperature. In the considered scenarios of climate change, climate warming will lead to an increase in the area of anoxic and hypoxic zones. Reduction of nutrient loading, estimated in accordance with the Baltic Sea Action Plan, will only be able to partially compensate for the negative effects of global warming.

  • 12.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Large-Scale Nutrient Dynamics in the Baltic Sea, 1970–20162018In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 5, article id 95Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea is one of the world's marine areas well-covered by both long-term observations and oceanographic studies. It is also a large coastal area in which eutrophication had already been recognized half a century ago. While the mechanisms of eutrophication are largely understood, several features are less recognized and sometimes neglected, including: (a) natural and anthropogenic North-South and East-West nutrient gradients within the drainage basin and marine ecosystems; (b) the compensatory potential of the interconnectivity between the Baltic Sea basins; (c) long nutrient residence times and high buffer capacity of the system, resulting in slow responses to nutrient load reductions. Particularly important is the interaction of (d) naturally occurring saltwater inflows sporadically ventilating deep water layers and (e) a partly man-made intensification of biological oxygen consumption. Resulting redox alterations of biogeochemical nitrogen and phosphorus cycles are locked in a “vicious circle” that promotes cyanobacterial nitrogen fixation, thereby hindering nitrogen load reduction and sustaining an elevated trophic state. This tight coupling of natural environmental variation and human impacts complicates both scientific studies and management recommendations. Our primary objective is to describe all these features and mechanisms with the best available data on nutrient loads, and unique estimates of the basin-wide nutrient pools. These data are presented as both long-term time series and empirical nutrient budgets. The analysis is supplemented by results of biogeochemical modeling. A second, more practical objective is to make these time series available to the community.

  • 13.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Myths of the Baltic Sea eutrophication2018In: Journal of Aquaculture & Marine Biology, ISSN 2378-3184, Vol. 7, no 2, p. 92-93Article in journal (Other academic)
  • 14. Schneider, Bernd
    et al.
    Dellwig, Olaf
    Kuliński, Karol
    Omstedt, Anders
    Pollehne, Falk
    Rehder, Gregor
    Savchuck, Oleg
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Biogeochemical cycles2017In: Biological Oceanography of the Baltic Sea / [ed] Pauline Snoeijs-Leijonmalm, Hendrik Schubert, Teresa Radziejewska, Dordrecht: Springer, 2017, p. 87-122Chapter in book (Refereed)
    Abstract [en]

    1. The internal cycles of carbon, nitrogen and phosphorus in the Baltic Sea are, like in other seas, mainly controlled by biological production and degradation of organic matter (OM).

    2. Biological activity also modulates the acid/base balance (pH), which is mainly a function of alkalinity and the total CO2 concentration.

    3. Particulate organic matter (POM) produced in the photic zone sinks into deeper water layers and is deposited on the sediment surface, where it is mineralised. Mineralisation is a form of microbial oxidation and thus leads to oxygen depletion. Due to its semi-enclosed position and its bottom topography, large-scale oxygen depletion of deep bottoms is common in the Baltic Sea.

    4. Under anoxic conditions, the burial of phosphorus bound to ferric oxide is inhibited and the availability of phosphate for incorporation in new OM production increases.

    5. In stagnant waters, the oxic/anoxic interface may migrate from the sediment into the water column, forming a pelagic redoxcline. Such a redoxcline occurs in large areas of the Baltic Sea.

    6. At oxygen concentrations close to zero, nitrate acts as an oxidant and is reduced to elemental nitrogen (denitrification). After the exhaustion of both oxygen and nitrate, OM is oxidised by sulphate, which is reduced to toxic hydrogen sulphide.

    7. The final step in the mineralisation process is the microbial formation of methane in deeper sediment layers, which reflects the internal oxidation/reduction of OM.

    8. A significant fraction of the organic carbon, nitrogen and phosphorus escapes mineralisation and is permanently buried in the sediment. On a long-term basis, this loss, together with export to the North Sea and internal sinks, is mainly balanced by riverine inputs and atmospheric deposition to the Baltic Sea.

  • 15. Vladimirova, Oksana M.
    et al.
    Eremina, Tatjana R.
    Isaev, Alexey V.
    Ryabchenko, Vladimir A.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. St. Petersburg State University, Russia.
    Modelling dissolved organic nutrients in the Gulf of Finland2018In: Fundamental and Applied Hydrophysics, ISSN 2073-6673, Vol. 11, no 4, p. 90-101Article in journal (Refereed)
    Abstract [en]

    St.-Petersburg model of eutrophication (SPBEM) has been modified for improving description of organic matter as apart of the nutrient biogeochemical cycles. The dynamics of labile and refractory fractions of dissolved organic nitrogenand phosphorus are now described with four additional equations. The modification was tested at the Gulf of Finland in anumerical experiment made with plausible initial and actual boundary conditions for the years 2009—2014. Comparisonof simulation with the available field observations indicates quite reasonable reproducibility of seasonal and inter-annualvariations of spatial distribution of hydrophysical and biogeochemical characteristics, including almost a perfect matchbetween simulated and observed dynamic of organic nutrients. The most important distinction from natural prototypesis the overestimated total amounts of inorganic nitrogen and phosphorus, which can be caused by the deficiencies inthe prescription of initial and boundary conditions as well as in the current parameterizations of pathways and rates ofmineralization fluxes. The finer tuning of SPBEM-2 requires more extensive sensitivity analysis.

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