| 1. |
- Bonaglia, Stefano, et al.
(författare)
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The fate of fixed nitrogen in marine sediments with low organic loading : an in situ study
- 2017
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 14:2, s. 285-300
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Tidskriftsartikel (refereegranskat)abstract
- Over the last decades, the impact of human activities on the global nitrogen (N) cycle has drastically increased. Consequently, benthic N cycling has mainly been studied in anthropogenically impacted estuaries and coasts, while in oligotrophic systems its understanding is still scarce. Here we report on benthic solute fluxes and on rates of denitrification, anammox, and dissimilatory nitrate reduction to ammonium (DNRA) studied by in situ incubations with benthic chamber landers during two cruises to the Gulf of Bothnia (GOB), a cold, oligotrophic basin located in the northern part of the Baltic Sea. Rates of N burial were also inferred to investigate the fate of fixed N in these sediments. Most of the total dissolved fixed nitrogen (TDN) diffusing to the water column was composed of organic N. Average rates of dinitrogen (N-2) production by denitrification and anammox (range: 53-360 mu mol Nm(-2) day(-1)) were comparable to those from Arctic and subarctic sediments worldwide (range: 34-344 mu mol Nm(-2) day(-1)). Anammox accounted for 18-26% of the total N2 production. Absence of free hydrogen sulfide and low concentrations of dissolved iron in sediment pore water suggested that denitrification and DNRA were driven by organic matter oxidation rather than chemolithotrophy. DNRA was as important as denitrification at a shallow, coastal station situated in the northern Bothnian Bay. At this pristine and fully oxygenated site, ammonium regeneration through DNRA contributed more than one-third to the TDN efflux and accounted, on average, for 45% of total nitrate reduction. At the offshore stations, the proportion of DNRA in relation to denitrification was lower (0-16% of total nitrate reduction). Median value and range of benthic DNRA rates from the GOB were comparable to those from the southern and central eutrophic Baltic Sea and other temperate estuaries and coasts in Europe. Therefore, our results contrast with the view that DNRA is negligible in cold and well-oxygenated sediments with low organic carbon loading. However, the mechanisms behind the variability in DNRA rates between our sites were not resolved. The GOB sediments were a major source (237 kt yr(-1), which corresponds to 184% of the external N load) of fixed N to the water column through recycling mechanisms. To our knowledge, our study is the first to document the simultaneous contribution of denitrification, DNRA, anammox, and TDN recycling combined with in situ measurements.
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| 2. |
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| 3. |
- Al-Saffar, Anas, 1969-, et al.
(författare)
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Parallel Changes in Harvey-Bradshaw Index, TNFα, and Intestinal Fatty Acid Binding Protein in Response to Infliximab in Crohn’s Disease
- 2017
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Ingår i: Gastroenterology Research and Practice. - Egypt : Hindawi Publishing Corporation. - 1687-6121 .- 1687-630X. ; , s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Intestinal fatty acid binding protein (I-FABP) indicates barrier integrity. Aims: determine if I-FABP is elevated in active Crohn's disease (CD) and if I-FABP parallels anti-TNF alpha antibody (infliximab) induced lowering of TNF alpha and Harvey-Bradshaw Index (HBI) as potential indicator of mucosal healing. I-FABP distribution along human gut was determined. Serum from 10 CD patients collected during first three consecutive infliximab treatments with matched pretreatment and follow-up samples one week after each treatment and corresponding HBI data were analyzed. I-FABP reference interval was established from 31 healthy subjects with normal gut permeability. I-FABP and TNF alpha were measured by ELISA; CRP was measured by nephelometry. Healthy tissue was used for I-FABP immunohistochemistry. Pretreatment CD patient TNF alpha was 1.6-fold higher than in-house reference interval, while I-FABP was 2.5-fold higher, which lowered at follow-ups. Combining all 30 infusion/follow-up pairs also revealed changes in I-FABP. HBI followed this pattern; CRP declined gradually. I-FABP was expressed in epithelium of stomach, jejunum, ileum, and colon, with the highest expression in jejunum and ileum. I-FABP is elevated in active CD with a magnitude comparable to TNF alpha. Parallel infliximab effects on TNF alpha, HBI, and I-FABP were found. I-FABP may be useful as an intestine selective prognostic marker in CD.
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| 4. |
- 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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| 5. |
- Atamanchuk, Dariia, 1987, et al.
(författare)
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Continuous long-term observations of the carbonate system dynamics in the water column of a temperate fjord
- 2015
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963. ; 148, s. 272-284
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Tidskriftsartikel (refereegranskat)abstract
- A cabled underwater observatory with more than 30 sensors delivering data in real-time was used to study the dynamics of the upper pelagic carbonate system of the Koljo Fjord, western Sweden, from September to April during two consecutive years (2011-2012 and 2012-2013). In the dynamic upper ca 15 m of the water column, salinity and temperature varied by up to 10 and 20 degrees C throughout the recorded periods, respectively. Partial pressure of CO2 (pCO(2)), measured with newly developed optical sensors (optodes) at three water depths (5, 9.6 and 12.6 m), varied between 210-940 mu atm, while O-2 varied between 80-470 mu mol/L. Redfield scaled graphs (Delta O-2:Delta DIC = -1.30), in which DIC was derived from pH or pCO(2) and salinity-derived alkalinity (A(Tsal)), and oxygen was measured by the sensors, were used as a tool to assess timing and occurrence of different processes influencing the dynamics of these parameters. Distinctive short-term variations of pCO(2) and O-2 were induced by either tidal oscillations, wind-driven water mass transport in the mixed layer or occasional transport of deep-basin water from below the thermo/halodine to the surface layer. Intensified air-sea gas exchange during short storm events was usually followed by stabilization of gas-related parameters in the water column, such as O-2 concentration and pCO(2), on longer time-scales characteristic for each parameter. Biological processes including organic matter degradation in late summer/autumn and primary production in early spring were responsible for slower and gradual seasonal changes of pCO(2) and O-2. Net primary production (NPP) rates in the Koljo Fjord were quantified to be 1.79 and 2.10 g C m(-2) during the spring bloom periods in 2012 and 2013, respectively, and ratios of 02 production:DIC consumption during the same periods were estimated to be -1.21 +/- 0.02 (at 5 m depth in 2013), -1.51 +/- 0.02 (at 12.6 m in 2012) and -1.95 +/- 0.05 (at 9.6 m in 2013). These ratios are discussed and compared to previously reported 02:C ratios during primary production. (C) 2015 Elsevier B.V. All rights reserved.
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| 6. |
- Atamanchuk, Dariia, 1987, et al.
(författare)
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Detection of CO2 leakage from a simulated sub-seabed storage site using three different types of pCO2 sensors
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 38, s. 121-134
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Tidskriftsartikel (refereegranskat)abstract
- This work is focused on results from a recent controlled sub-seabed in situ carbon dioxide (CO2) releaseexperiment carried out during May–October 2012 in Ardmucknish Bay on the Scottish west coast. Threetypes of pCO2sensors (fluorescence, NDIR and ISFET-based technologies) were used in combination withmultiparameter instruments measuring oxygen, temperature, salinity and currents in the water columnat the epicentre of release and further away. It was shown that distribution of seafloor CO2 emissionsfeatures high spatial and temporal heterogeneity. The highest pCO2values (∼1250 atm) were detectedat low tide around a bubble stream and within centimetres distance from the seafloor. Further up in thewater column, 30–100 cm above the seabed, the gradients decreased, but continued to indicate elevatedpCO2at the epicentre of release throughout the injection campaign with the peak values between 400and 740atm. High-frequency parallel measurements from two instruments placed within 1 m fromeach other, relocation of one of the instruments at the release site and 2D horizontal mapping of therelease and control sites confirmed a localized impact from CO2emissions. Observed effects on the watercolumn were temporary and post-injection recovery took <7 days.A multivariate statistical approach was used to recognize the periods when the system was dominatedby natural forcing with strong correlation between variation in pCO2and O2, and when it was influencedby purposefully released CO2.Use of a hydrodynamic circulation model, calibrated with in situ data, was crucial to establishingbackground conditions in this complex and dynamic shallow water system.
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| 7. |
- Best, Mairi M. R., et al.
(författare)
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The EMSO-ERIC Pan-European Consortium: Data Benefits and Lessons Learned as the Legal Entity Forms
- 2016
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Ingår i: Marine Technology Society journal. - 0025-3324. ; 50:3, s. 8-15
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Tidskriftsartikel (refereegranskat)abstract
- The European Multidisciplinary Seafloor and water-column Observatory (EMSO) European Research Infrastructure Consortium (ERIC) provides power, communications, sensors, and data infrastructure for continuous, high-resolution, (near-)real-time, interactive ocean observations across a multidisciplinary and interdisciplinary range of research areas including biology, geology, chemistry, physics, engineering, and computer science, from polar to subtropical environments, through the water column down to the abyss. Eleven deep-sea and four shallow nodes span from the Arctic through the Atlantic and Mediterranean, to the Black Sea. Coordination among the consortium nodes is being strengthened through the EMSOdev project (H2020), which will produce the EMSO Generic Instrument Module (EGIM). Early installations are now being upgraded, for example, at the Ligurian, Ionian, Azores, and Porcupine Abyssal Plain (PAP) nodes. Significant findings have been flowing in over the years; for example, high-frequency surface and subsurface water-column measurements of the PAP node show an increase in seawater pCO2 (from 339 μatm in 2003 to 353 μatm in 2011) with little variability in the mean air-sea CO2 flux. In the Central Eastern Atlantic, the Oceanic Platform of the Canary Islands open-ocean canary node (aka ESTOC station) has a long-standing time series on water column physical, biogeochemical, and acidification processes that have contributed to the assessment efforts of the Intergovernmental Panel on Climate Change (IPCC). EMSO not only brings together countries and disciplines but also allows the pooling of resources and coordination to assemble harmonized data into a comprehensive regional ocean picture, which will then be made available to researchers and stakeholders worldwide on an open and interoperable access basis.
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| 8. |
- Blomqvist, Sven, et al.
(författare)
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Long overdue improvement of box corer sampling
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 538, s. 13-21
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Tidskriftsartikel (refereegranskat)abstract
- An improved, large double-jawed box corer, intended primarily for sampling of soft sediments on continental margins and in large lakes, is described. The device performs reliably when entering the sediment and enclosing the sample, during withdrawal and hoisting on board the ship and also when detaching the collected sediment sample. It offers the following advantages: (1) robust design, (2) minimally impeded flow of water through the box chamber during lowering and (3) an efficient closure mechanism. It is furnished with a supporting stand, a transparent liner and an accessory anti-slosh baffle for insertion in the liner as the corer is set down on the ship's deck. In situ video records and turbidity measurements from field trials, as well as visual inspection of the core and supernatant water after retrieval, show that the device collects minimally disturbed sediment when properly and carefully operated. This contrasts with the bulky United States Naval Electronics Laboratory (USNEL) Spade Corer in which water flow through the box chamber during lowering is impeded, causing a bow-wave ahead of the corer that displaces surficial sediment. In addition, the USNEL's single-spade closing mechanism deforms the sediment sample severely and can even cause loss of sediment. Our new box corer performs much better, making it suitable for quantitative benthic sampling.
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| 9. |
- Bonaglia, Stefano, et al.
(författare)
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Sulfide oxidation in deep Baltic Sea sediments upon oxygenation and colonization by macrofauna
- 2019
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 166
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Tidskriftsartikel (refereegranskat)abstract
- Coastal and shelf sediments affected by transient or long-term bottom water anoxia and sulfidic conditions undergo drastic changes in macrofauna communities and abundances. This study investigates how early colonization by two macrofaunal functional traits (epifauna vs. infauna) affects oxygen, sulfide, and pH dynamics in anoxic sediment upon recent bottom water oxygenation. Large mesocosms (area 900 cm(2)) with 150-m-deep Baltic Sea soft sediments were exposed to three treatments: (1) no animals; (2) addition of 170 polychaetes (Marenzelleria arctia); (3) addition of 181 amphipods (Monoporeia affinis). Porewater chemistry was investigated repeatedly by microsensor profiling over a period of 65 days. Colonization by macrofauna did not significantly deepen penetration of oxygen compared to the animal-free sediment. Bioturbation by M. affinis increased the volume of the oxidized, sulfide-free sediment by 66% compared to the animal-free control already after 13 days of incubation. By the end of the experiment M. affinis and M. arctia increased the oxidized sediment volume by 87 and 35%, respectively. Higher efficiency of epifaunal amphipods in removing hydrogen sulfide than deep-burrowing polychaetes is likely due to more substantial re-oxidation of manganese and/or nitrogen compounds associated with amphipod mixing activity. Our results thus indicate that early colonization of different functional groups might have important implications for the later colonization by benthic macrofauna, meiofauna and microbial communities that benefit from oxidized and sulfide-free sediments.
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| 10. |
- De Brabandere, L., et al.
(författare)
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Oxygenation of an anoxic fjord basin strongly stimulates benthic denitrification and DNRA
- 2015
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 126:1, s. 131-152
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Tidskriftsartikel (refereegranskat)abstract
- © 2015 Springer International Publishing Switzerland Hypoxia hampers eutrophication reduction efforts by enabling high nutrient fluxes from sediment to bottom waters. Oxygenation of hypoxic water bodies is often proposed to reduce benthic ammonium and phosphate release. This study investigates the functional response of benthic nitrate-reducing processes to a long-term engineered oxygenation effort in a density-stratified fjord with euxinic bottom waters. Oxygenation was achieved by mixing surface water with deep, euxinic water, which increased oxygen and nitrate concentrations in the deep water column. The presence of nitrate instigated benthic nitrate reduction in the newly oxidized sediments by equally stimulating denitrification and dissimilatory nitrate reduction to ammonium (DNRA). DNRA and total nitrate reduction rates, as well as the contribution of DNRA to total nitrate reduction, decreased with increasing exposure time of the sediments to oxygen. The relative importance of DNRA as a nitrate sink was correlated to nitrate concentrations, with more nitrate being reduced to ammonium at higher bottom water nitrate concentrations. Overall, engineered oxygenation decreased the net efflux of dissolved inorganic nitrogen from the sediments by stimulating net nitrate removal through denitrification.
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