| 1. |
- Berezina, Anfisa, et al.
(author)
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Modelling the Influence from Biota and Organic Matter on the Transport Dynamics of Microplastics in the Water Column and Bottom Sediments in the Oslo Fjord
- 2021
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In: Water. - : MDPI AG. - 2073-4441. ; 13:19
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Journal article (peer-reviewed)abstract
- The fate of microplastics (MP) in seawater is heavily influenced by the biota: the density of MP particles can be changed due to biofouling, which affects sinking, or MP can be digested by zooplankton and transferred into fecal pellets with increased sinking rate. We hypothesize that seasonal production and degradation of organic matter, and corresponding changes in the plankton ecosystem affect the MP capacity for transportation and burying in sediments in different seasons. This is simulated with a coupled hydrodynamical-biogeochemical model that provides a baseline scenario of the seasonal changes in the planktonic ecosystem and changes in the availability of particulate and dissolved organic matter. In this work, we use a biogeochemical model OxyDep that simulates seasonal changes of phytoplankton (PHY), zooplankton (HET), dissolved organic matter (DOM) and detritus (POM). A specifically designed MP module considers MP particles as free particles (MPfree), particles with biofouling (MPbiof), particles consumed by zooplankton (MPhet) and particles in detritus, including fecal pellets (MPdet). A 2D coupled benthic-pelagic vertical transport model 2DBP was applied to study the effect of seasonality on lateral transport of MP and its burying in the sediments. OxyDep and MP modules were coupled with 2DBP using Framework for Aquatic Biogeochemical Modelling (FABM). A depletion of MP from the surface water and acceleration of MP burying in summer period compared to the winter was simulated numerically. The calculations confirm the observations that the “biological pump” can be one of the important drivers controlling the quantity and the distribution of MP in the water column.
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| 2. |
- Bernd, Schneider, et al.
(author)
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Biogeochemical cycles : Biological Oceanography of the Baltic Sea
- 2017
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In: Springer. - Dordrecht : Springer. - 9789400706675 ; , s. 87-122
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Book chapter (peer-reviewed)abstract
- 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.
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| 3. |
- Conley, Daniel, et al.
(author)
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Hypoxia-Related Processes in the Baltic Sea
- 2009
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:10, s. 3412-3420
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
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| 5. |
- Ehrnsten, Eva, et al.
(author)
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Modelling the effects of benthic fauna on carbon, nitrogen and phosphorus dynamics in the Baltic Sea
- 2022
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In: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 19:13, s. 3337-3367
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Journal article (peer-reviewed)abstract
- Even though the effects of benthic fauna on aquatic biogeochemistry have been long recognized, few studies have addressed the combined effects of animal bioturbation and metabolism on ecosystem–level carbon and nutrient dynamics. Here we merge a model of benthic fauna (BMM) into a physical–biogeochemical ecosystem model (BALTSEM) to study the long-term and large-scale effects of benthic fauna on nutrient and carbon cycling in the Baltic Sea. We include both the direct effects of faunal growth and metabolism and the indirect effects of its bioturbating activities on biogeochemical fluxes of and transformations between organic and inorganic forms of carbon (C), nitrogen (N), phosphorus (P) and oxygen (O). Analyses of simulation results from the Baltic Proper and Gulf of Riga indicate that benthic fauna makes up a small portion of seafloor active organic stocks (on average 1 %–4 % in 2000–2020) but contributes considerably to benthic–pelagic fluxes of inorganic C (23 %–31 %), N (42 %–51 %) and P (25 %–34 %) through its metabolism. Results also suggest that the relative contribution of fauna to the mineralization of sediment organic matter increases with increasing nutrient loads. Further, through enhanced sediment oxygenation, bioturbation decreases benthic denitrification and increases P retention, the latter having far-reaching consequences throughout the ecosystem. Reduced benthic–pelagic P fluxes lead to a reduction in N fixation and primary production, lower organic matter sedimentation fluxes, and thereby generally lower benthic stocks and fluxes of C, N and P. This chain of effects through the ecosystem overrides the local effects of faunal respiration, excretion and bioturbation. Due to large uncertainties related to the parameterization of benthic processes, we consider this modelling study a first step towards disentangling the complex ecosystem-scale effects of benthic fauna on biogeochemical cycling.
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| 6. |
- Ehrnsten, Eva, et al.
(author)
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Understanding Environmental Changes in Temperate Coastal Seas : Linking Models of Benthic Fauna to Carbon and Nutrient Fluxes
- 2020
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In: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 7
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Research review (peer-reviewed)abstract
- Coastal seas are highly productive systems, providing an array of ecosystem services to humankind, such as processing of nutrient effluents from land and climate regulation. However, coastal ecosystems are threatened by human-induced pressures such as climate change and eutrophication. In the coastal zone, the fluxes and transformations of nutrients and carbon sustaining coastal ecosystem functions and services are strongly regulated by benthic biological and chemical processes. Thus, to understand and quantify how coastal ecosystems respond to environmental change, mechanistic modeling of benthic biogeochemical processes is required. Here, we discuss the present model capabilities to quantitatively describe how benthic fauna drives nutrient and carbon processing in the coastal zone. There are a multitude of modeling approaches of different complexity, but a thorough mechanistic description of benthic-pelagic processes is still hampered by a fundamental lack of scientific understanding of the diverse interactions between the physical, chemical and biological processes that drive biogeochemical fluxes in the coastal zone. Especially shallow systems with long water residence times are sensitive to the activities of benthic organisms. Hence, including and improving the description of benthic biomass and metabolism in sediment diagenetic as well as ecosystem models for such systems is essential to increase our understanding of their response to environmental changes and the role of coastal sediments in nutrient and carbon cycling. Major challenges and research priorities are (1) to couple the dynamics of zoobenthic biomass and metabolism to sediment reactive-transport in models, (2) to test and validate model formulations against real-world data to better incorporate the context-dependency of processes in heterogeneous coastal areas in models and (3) to capture the role of stochastic events.
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| 7. |
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| 8. |
- Gustafsson, Bo G., et al.
(author)
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Load scenarios for Ecosupport : Technical Report No. 4
- 2011
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Reports (other academic/artistic)abstract
- In the project ECOSUPPORT, three coupled physical-biogeochemical models (ER-GOM, RCO-SCOBI and BALTSEM) are used to produce an ensemble of combine climate change - nutrient load scenarios. The atmospheric driving forces for the models are produced by two global climate models, ECHAM5 and HadCM3; and these results are dynamically downscaled using the RCAO model at the SMHI, see Meier et al. (2011) and references therein. Since, results from dynamic hydrological models were not available, river runoff were constructed from the net P-E balance of the RCAO model results. Nutrient load scenarios wasto be explicitly given, but effects from climate change induced river runoff variations were estimated. In total, four different climate change scenarios produced and four different assumptions on direct anthropogenic changes in nutrient loads, thus in total 16 combinations. The nutrient load scenarios comprised of; one reference with approximately unchanged loads, one pessimistic business as usual and two more optimistic, current legislation and Baltic Sea Action Plan. All the latter based on previous work. This report describes the construction of these nutrient load scenarios.
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| 9. |
- Gustafsson, Bo G., et al.
(author)
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Reconstructing the Development of Baltic Sea Eutrophication 1850-2006
- 2012
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In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 41:6, s. 534-548
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Journal article (peer-reviewed)abstract
- 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.
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