| 1. |
- Almroth Rosell, Elin, 1977, et al.
(författare)
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A new approach to model oxygen dependent benthic phosphate fluxes in the Baltic Sea
- 2015
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 144, s. 127-141
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Tidskriftsartikel (refereegranskat)abstract
- The new approach to model the oxygen dependent phosphate release by implementing formulations of the oxygen penetration depths (OPD) and mineral bound inorganic phosphorus pools to the Swedish Coastal and Ocean Biogeochemical model (SCOBI) is described. The phosphorus dynamics and the oxygen concentrations in the Baltic proper sediment are studied during the period 1980-2008 using SCOBI coupled to the 3D-Rossby Centre Ocean model. Model data are compared to observations from monitoring stations and experiments. The impact from oxygen consumption on the determination of the OPD is found to be largest in the coastal zones where also the largest OPD are found. In the deep water the low oxygen concentrations mainly determine the OPD. Highest modelled release rate of phosphate from the sediment is about 59 x 10(3) t P year(-1) and is found on anoxic sediment at depths between 60-150 m, corresponding to 17% of the Baltic proper total area. The deposition of organic and inorganic phosphorus on sediments with oxic bottom water is larger than the release of phosphorus, about 43 x 10(3) t P year(-1). For anoxic bottoms the release of total phosphorus during the investigated period is larger than the deposition, about 19 x 10(3) t P year(-1). In total the net Baltic proper sediment sink is about 23.7 x 10(3) t P year(-1). The estimated phosphorus sink efficiency of the entire Baltic Sea is on average about 83% during the period.
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| 2. |
- Almroth Rosell, Elin, 1977, et al.
(författare)
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Effects of simulated natural and massive resuspension on benthic oxygen, nutrient and dissolved inorganic carbon fluxes in Loch Creran, Scotland
- 2012
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Ingår i: Journal of Sea Research. - : Elsevier BV. - 1385-1101. ; 72, s. 38-48
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Tidskriftsartikel (refereegranskat)abstract
- The effect of repeated natural resuspension on benthic oxygen consumption and the effect of natural and massive resuspension on oxygen consumption and fluxes of phosphate, silicate, ammonium and dissolved inorganic carbon (DIC) were studied at two stations (S1 and S2) in a Scottish sea loch. Station S11 had organically enriched sediment and station S1 had lower organic content in the sediment. The fluxes were measured in situ using the Göteborg benthic lander. Natural resuspension, simulating resuspension events due to strong wind, waves or currents, and massive resuspension, simulating resuspension due to e.g. trawling or dredging, were created inside the incubation chambers by regulating the stirring of the incubated overlying water or by retracting and shaking the incubated sediment. Natural resuspension showed clear effects on the oxygen consumption at station S11, where it increased with an average of 12.8 (standard error (s.e.) 0.17) and 7.7 (s.e. 0.12) mmol m− 2 d− 1 during the first and second incubations, respectively. At station S1 there was no clear effect of natural resuspension on the oxygen consumption. Massive resuspension increased the oxygen consumption on S1 with an average of 608 (standard deviation (sd) 366) mmol m− 2 d− 1 and on S11 with an average of 2396 (sd 2265) mmol m− 2 d− 1. The fluxes of ammonium, phosphate and silicate were affected by the massive resuspension in 50, 14 and 33% of the chambers, respectively, on station S11. However, in the majority of the cases there were no effects on the nutrient and DIC fluxes of massive resuspension. The absolute concentrations of DIC, ammonium and silicate did however instantly increase with an average of 419 (sd 297), 48 (sd 27) and 6.9 (sd 3.7) μM, respectively, at S11 upon massive resuspension. The concentrations of phosphate decreased instantly with an average of 0.2 (sd 0.1) μM. On station S1 there were effects only on the ammonium and silicate concentrations, which increased with 0.8 (sd 0.3) and 1.13 (sd 0.36) μM, respectively. The large increase in oxygen consumption due to massive resuspension indicates that activities like e.g. trawling and dredging that take place in areas where water exchange occurs infrequently may lead to oxygen depletion in bottom water, which in turn might affect the ecological balance. Silicate, ammonium and DIC can be released due to massive resuspension and contribute to increased algal blooms in surface waters.
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| 3. |
- Almroth Rosell, Elin, 1977
(författare)
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Influence of resuspension on sediment-water solute exchange and particle transport in marine environments
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Marine sediments contain a large pool of nutrients, which if released would contribute to increased eutrophication, in spite of decreased nutrient loads from land and atmosphere. Resuspension is a process, which might influence the release of nutrients from the sediment to the overlying water. The influence of resuspension on benthic fluxes of oxygen, dissolved inorganic carbon (DIC), nutrients, dissolved iron (dFe) and dissolved manganese (dMn) was therefore investigated in three different marine environments. The measurements were performed using a benthic lander with the advantage of operating in situ. The method of measuring the effects of resuspension was developed in the archipelago of Gothenburg (Paper I). This method was then further improved and used during field studies in the Gulf of Finland (GoF; Paper II) and in a Scottish sea loch (Paper III). During the latter study also the effects of massive (simulating dredging or trawling) and repeated resuspension events on the benthic fluxes were studied. Natural resuspension significantly increased the oxygen consumption in the GoF and at a station with organic rich sediment in Scotland. There were no significant effects of natural resuspension on nutrient, DIC and dMn fluxes, but the fluxes and concentrations of dFe increased at stations with low bottom water oxygen concentrations (GoF). Massive resuspension increased the oxygen consumption enormously and instantly changed the bottom water concentrations of phosphate (which decreased), DIC, silicate and ammonium (which increased). Results confirmed that the general magnitude of phosphate fluxes was dependent on the oxygen regime (GoF; Paper IV). However, results also showed a strong correlation between phosphate and DIC fluxes during anoxic conditions implying that phosphate fluxes are controlled by input and degradation of organic matter under anoxia. The internal load was calculated to be about 66 000 ton P yr-1 in the GoF. If all oxic bottoms below 40 m would turn anoxic the internal load was computed to increase with about 35 000 ton P yr-1. Results from a fully coupled high-resolution biogeochemical-physical ocean model, including an empirical wave model, showed that a large fraction of the sedimentary organic carbon has at least once been resuspended, and the largest contribution of resuspended organic matter to the total transport of particulate organic matter occurred at shallow transport and erosion bottoms (long-term average, 1979-2007) in the Baltic Sea (Paper V). The fraction of resuspended organic matter in the deepest areas of the Baltic Sea was low (< 10%) even though there was a large horizontal transport of suspended organic matter and a high sedimentary content of it. A map of different bottom types, accumulation, transport and erosion bottoms, was also created.
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| 4. |
- Almroth Rosell, Elin, 1977, et al.
(författare)
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Transport of fresh and resuspended particulate organic material in the Baltic Sea — a model study
- 2011
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963. ; 87:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- A fully coupled high-resolution 3-dimensional biogeochemical–physical ocean model including an empirical wave model was used to investigate the long-term average (1970–2007) distributions and transports of resuspended matter and other types of suspended organic matter in the Baltic Sea. Modelled bottom types were compared to observations and the results showed that the model successfully managed to capture the horizontal, as well as the vertical, distribution of the different bottom types: accumulation, transport and erosion bottoms. The model also captured well the nutrient element contents in the sediments. On average the largest contribution of resuspended organic carbon to the transport of total organic carbon is found at erosion and transport bottoms. Although the relative transport of resuspended organic carbon at deeper accumulation bottoms in general is low (< 10% of total), the central parts of the sub-basins act on average as sinks that import organic matter while the more shallow areas and the coastal regions acts as sources of organic carbon in the water column. This indicates that the particulate organic matter produced in erosion and transport areas might be kept in suspension long enough to be transported and settle in less energetic areas, i.e. on accumulation bottoms.
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| 5. |
- Cathalot, C., et al.
(författare)
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Spatial and Temporal Variability of Benthic Respiration in a Scottish Sea Loch Impacted by Fish Farming: A Combination of In Situ Techniques
- 2012
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Ingår i: Aquatic geochemistry. - : Springer Science and Business Media LLC. - 1380-6165 .- 1573-1421. ; 18:6, s. 515-541
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Tidskriftsartikel (refereegranskat)abstract
- The effects of fish farm activities on sediment biogeochemistry were investigated in Loch Creran (Western Scotland) from March to October 2006. Sediment oxygen uptake rates (SOU) were estimated along an organic matter gradient generated from an Atlantic salmon farm using a combination of in situ techniques: microelectrodes, planar optode and benthic chamber incubations. Sulphide (H2S) and pH distributions in sediment porewater were also measured using in situ microelectrodes, and dissolved inorganic carbon (DIC) fluxes were measured in situ using benthic chambers. Relationships between benthic fluxes, vertical distribution of oxidants and reduced compounds in the sediment were examined as well as bacterial abundance and biomass. Seasonal variations in SOU were relatively low and mainly driven by seasonal temperature variations. The effect of the fish farm on sediment oxygen uptake rate was clearly identified by higher total and diffusive oxygen uptake rates (TOU and DOU, respectively) on impacted stations (TOU: 70 ± 25 mmol O2 m-2 day-1; DOU: 70 ± 32 mmol O2 m-2 day-1 recalculated at the summer temperature), compared with the reference station (TOU: 28.3 ± 5.5 mmol O2 m-2 day-1; DOU: 21.5 ± 4.5 mmol O2 m-2 day-1). At the impacted stations, planar optode images displayed high centimetre scale heterogeneity in oxygen distribution underlining the control of oxygen dynamics by small-scale processes. The organic carbon enrichment led to enhanced sulphate reduction as demonstrated by large vertical H2S concentration gradients in the porewater (from 0 to 1,000 lM in the top 3 cm) at the most impacted site. The impact on ecosystem functions such as bioirrigation was evidenced by a decreasing TOU/DOU ratio, from 1.7 in the non-impacted sediments to 1 in the impacted zone. This trend was related to a shift in the macrofaunal assemblage and an increase in sediment bacterial population. The turnover time of the organic load of the sediment was estimated to be over 6 years.
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| 6. |
- Eilola, Kari, et al.
(författare)
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SMHI reportsSMHI rep., Oceanogr : Swedish Meteorological and Hydrological Institute reports. OceanographySMHISMHI report. Oceanography 2007:37OceanographyROSMHI RO
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is related to the BONUS project “Nutrient Cocktails in COAstal zones of the Baltic Sea” alias COCOA. The aim of BONUS COCOA is to investigate physical, biogeochemical and biological processes in a combined and coordinated fashion to improve the understanding of the interaction of these processes on the removal of nutrients along the land -sea interface. The report is especially related to BONUS COCOA WP 6 in which the main objective is extrapolation of results from the BONUS COCOA learning sites to coastal sites around the Baltic Sea in general. Specific objectives of this deliverable (D6.4) were to connect observed process rates with modelling data and ecosystem characteristics.In the report we made statistical analyses of observations from BONUS COCOA study sites together with results from the Swedish Coastal zone Model (SCM). Eight structural variables (water depth, temperature, salinity, bottom water concentrations of oxygen, ammonium, nitrate and phosphate, as well as nitrogen content in sediment) were found common to both the experimentally determined and the model data sets. The observed process rate evaluated in this report was denitrification. In addition regressions were tested between observed denitrification rates and several structural variables (lat itude, longitude, depth, light, temperature, salinity, grain class, porosity, loss of ignition, sediment organic carbon, total nitrogen content in the sediment, sediment carbon/nitrogen-ratio, sediment chlorphyll-a as well as bottom water concentrations of oxygen, ammonium, nitrate, and dissolved inorganic phosphorus and silicate) for pooled data from all learning sites.The statistical results showed that experimentally determined multivariate data set from the shallow, illuminated stations was mainly found to be similar to the multivariate data set produced by the SCM model. Generally, no strong correlations of simple relations between observed denitrification and available structural variables were found for data collected from all the learning sites. We found some non-significant correlation between denitrification rates and bottom water dissolved inorganic phosphorous and dissolved silica but the reason behind the correlations is not clear.We also developed and evaluated a theory to relate process rates to monitoring data and nutrient retention. The theoretical analysis included nutrient retention due to denitrification as well as burial of phosphorus and nitrogen. The theory of nutrient retention showed good correlations with model results. It was found that area-specific nitrogen and phosphorus retention capacity in a sub-basin depend much on mean water depth, water residence time, basin area and the mean nutrient concentrations in the active sediment layer and in the water column.
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| 7. |
- Hylén, Astrid, 1991, et al.
(författare)
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Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale
- 2021
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 18, s. 2981-3004
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom water conditions, phosphorus release from the sediment is elevated, which further stimulates primary production. It is commonly assumed that re-oxygenation could break this “vicious cycle” by increasing the sedimentary phosphorus retention. Recently, a deep-water inflow into the Baltic Sea created a natural in situ experiment that allowed us to investigate if temporary re-oxygenation stimulates sedimentary retention of dissolved inorganic phosphorus (DIP). Surprisingly, during this 3-year study, we observed a transient but considerable increase, rather than a decrease, in the sediment efflux of DIP and other dissolved biogenic compounds. This suggested that the oxygenated inflow elevated the organic matter degradation in the sediment, likely due to an increase in organic matter supply to the deeper basins, potentially combined with a transient stimulation of the mineralisation efficiency. As a result, the net sedimentary DIP release per m2 was 56%–112% higher over the years following the re-oxygenation than before. In contrast to previous assumptions, our results show that inflows of oxygenated water to anoxic bottom waters can increase the sedimentary phosphorus release.
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| 8. |
- Nilsson, Madeleine, et al.
(författare)
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Particle shuttling and oxidation capacity of sedimentary organic carbon on the Baltic Sea system scale
- 2021
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 232
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Tidskriftsartikel (refereegranskat)abstract
- Continental margin sediments receive most of the particulate organic carbon (POC) deposited on the global seafloor, making them crucial locations in the carbon cycle. However, the complex environments in coastal oceans make it challenging to predict the fate of sedimentary organic carbon (OC) in these areas. Here we use data from 21 sites in the Baltic Sea, representing different biological and physiochemical regimes, to explore controls on sedimentary OC cycling. To this end, we combine in situ measured benthic fluxes of dissolved inorganic carbon (DIC; proxy for OC oxidation) with data on sediment properties. In the Gulf of Bothnia, low sedimentary OC oxidation capacities (yearly DIC flux divided by sedimentary POC inventory) were likely caused by a large fraction of terrestrial material in the POC pool, indicated by low sedimentary chlorophyll a content and high (> 10) carbon:nitrogen ratios. The highest OC oxidation capacities were measured at shallow, permanently oxic sites in the Baltic Proper, where bioturbation likely stimulates OC oxidation. The other sites in the Baltic Proper and all stations in the Gulf of Finland displayed increasing OC oxidation capacities with increasing normalised water depth (station depth divided by maximal depth in the basin). This pattern suggests that substantial quantities of POC are shuttled, through repeated cycles of resuspension-redeposition, from shallow erosion-transport (ET) areas to deep accumulation (A) areas. This interpretation was supported by decreasing sediment age and increasing sedimentary inventories of POC and chlorophyll a with normalised water depth. Our calculations indicate that particle shuttling redistributes almost half of the deposited export production from ET areas to A areas in the Baltic Proper, and that substantial amounts of terrestrial organic material are transported through particle shuttling to the deeper parts of the Gulf of Finland and Gulf of Bothnia. Depositional setting and POC origin can thus be central factors in predicting the distribution and fate of OC in coastal and shelf sediments.
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| 9. |
- Viktorsson, Lena, 1980, et al.
(författare)
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Benthic phosphorus dynamics in the Gulf of Finland, Baltic Sea
- 2012
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Ingår i: Aquatic geochemistry. - : Springer Science and Business Media LLC. - 1380-6165 .- 1573-1421. ; 18, s. 543-564
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Tidskriftsartikel (refereegranskat)abstract
- Benthic fluxes of soluble reactive phosphorus (SRP) and dissolved inorganic carbon (DIC) were measured in situ using autonomous landers in the Gulf of Finland in the Baltic Sea, on four expeditions between 2002 and 2005. These measurements together with model estimates of bottom water oxygen conditions were used to compute the magnitude of the yearly integrated benthic SRP flux (also called internal phosphorus load). The yearly integrated benthic SRP flux was found to be almost 10 times larger than the external (river and land sources) phosphorus load. The average SRP flux was 1.25 ± 0.56 mmol m-2 d-1 on anoxic bottoms, and -0.01 ± 0.08 mmol m-2 d-1 on oxic bottoms. The bottom water oxygen conditions determined whether the SRP flux was in a high or low regime, and degradation of organic matter (as estimated from benthic DIC fluxes) correlated positively with SRP fluxes on anoxic bottoms. From this correlation, we estimated a potential increase in phosphorus flux of 0.69 ± 0.26 mmol m-2 d-1 from presently oxic bottoms, if they would turn anoxic. An almost full annual data set of in situ bottom water oxygen measurements showed high variability of oxygen concentration. Because of this, an estimate of the time which the sediments were exposed to oxygenated overlying bottom water was computed using a coupled thermohydrodynamic ocean–sea and ecosystem model. Total phosphorus burial rates were calculated from vertical profiles of total phosphorus in sediment and sediment accumulation rates. Recycling and burial efficiencies for phosphorus of 97 and 3%, respectively, were estimated for anoxic accumulation bottoms from a benthic mass balance, which was based on the measured effluxes and burial rates.
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