| 1. |
- Sundbäck, Kristina, 1949, et al.
(författare)
-
Importance of benthic nutrient regeneration during initiation of macroalgal blooms in shallow bays
- 2003
-
Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 246, s. 115-126
-
Tidskriftsartikel (refereegranskat)abstract
- Fast growing ephemeral algae are increasingly observed in shallow coastal waters worldwide. This is generally considered a symptom of coastal eutrophication. It has been suggested that the reoccurrence of macroalgal mats, despite ongoing efforts to decrease nutrient loadings, may be explained by the fact that sheltered bays function as self-regenerating systems through benthic regeneration of nutrients. The importance of benthic nutrient regeneration during the initiation of the growth of filamentous green algal mats was investigated in 2 shallow-water bays on the west coast of Sweden. Nutrient regeneration was assessed in situ and in the laboratory, using sediment-water light/dark incubations and pore water distribution patterns. Benthic efflux of inorganic nutrients could supply up to 55 to 100% of the estimated nitrogen demand and 30 to 70% of the phosphorus requirements for the initial macroalgal growth from May to June. However, the availability of the pore water nutrient pool was influenced by the amount and functional type of infauna, and by competition from microphytobenthos. Because of the internal nutrient source of the embayments, it is suggested that there may be a significant time lag between a decreased nutrient supply to coastal waters and improved conditions of shallow water embayments.
|
|
| 2. |
- Thompson, Luke R., et al.
(författare)
-
A communal catalogue reveals Earth's multiscale microbial diversity
- 2017
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 551:7681, s. 457-463
-
Tidskriftsartikel (refereegranskat)abstract
- © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Our growing awareness of the microbial world's importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth's microbial diversity.
|
|
| 3. |
- Alsterberg, Christian, 1982, et al.
(författare)
-
Functioning of a Shallow-Water Sediment System during Experimental Warming and Nutrient Enrichment
- 2012
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 7:12
-
Tidskriftsartikel (refereegranskat)abstract
- Effects of warming and nutrient enrichment on intact unvegetated shallow-water sediment were investigated for 5 weeks in the autumn under simulated natural field conditions, with a main focus on trophic state and benthic nitrogen cycling. In a flow-through system, sediment was exposed to either seawater at ambient temperature or seawater heated 4 degrees C above ambient, with either natural or nutrient enriched water. Sediment-water fluxes of oxygen and inorganic nutrients, nitrogen mineralization, and denitrification were measured. Warming resulted in an earlier shift to net heterotrophy due to increased community respiration; primary production was not affected by temperature but (slightly) by nutrient enrichment. The heterotrophic state was, however, not further strengthened by warming, but was rather weakened, probably because increased mineralization induced a shortage of labile organic matter. Climate-related warming of seawater during autumn could therefore, in contrast to previous predictions, induce shorter but more intensive heterotrophic periods in shallow-water sediments, followed by longer autotrophic periods. Increased nitrogen mineralization and subsequent effluxes of ammonium during warming suggested a preferential response of organisms driving nitrogen mineralization when compared to sinks of ammonium such as nitrification and algal assimilation. Warming and nutrient enrichment resulted in non-additive effects on nitrogen mineralization and denitrification (synergism), as well as on benthic fluxes of phosphate (antagonism). The mode of interaction appears to be related to the trophic level of the organisms that are the main drivers of the affected processes. Despite the weak response of benthic microalgae to both warming and nutrient enrichment, the assimilation of nitrogen by microalgae was similar in magnitude to rates of nitrogen mineralization. This implies a sustained filter function and retention capacity of nutrients by the sediment.
|
|
| 4. |
- Alsterberg, Christian, 1982, et al.
(författare)
-
Habitat diversity and ecosystem multifunctionality-The importance of direct and indirect effects
- 2017
-
Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 3:2
-
Tidskriftsartikel (refereegranskat)abstract
- Ecosystems worldwide are facing habitat homogenization due to human activities. Although it is commonly proposed that such habitat homogenization can have negative repercussions for ecosystem functioning, this question has yet to receive explicit scientific attention. We expand on the framework for evaluating the functional consequences of bio-diversity loss by scaling up from the level of species to the level of the entire habitats. Just as species diversity generally fosters ecosystem functioning through positive interspecies interactions, we hypothesize that different habitats within ecosystems can facilitate each other through structural complementarity and through exchange of material and energy across habitats. We show that experimental ecosystems comprised of a diversity of habitats show higher levels of multiple ecosystem functions than ecosystems with low habitat diversity. Our results demonstrate that the effect of habitat diversity on multifunctionality varies with season; it has direct effects on ecosystem functioning in summer and indirect effects, via changes in species diversity, in autumn, but no effect in spring. We propose that joint consideration of habitat diversity and species diversity will prove valuable for both environmental management and basic research.
|
|
| 5. |
- Alsterberg, Christian, 1982, et al.
(författare)
-
Response of a shallow-water sediment system to warming
- 2011
-
Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590. ; 56:6, s. 2147-2160
-
Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: Effects of predicted global warming (+4°C) on the structure and function of a temperate shallow-water sediment system were studied for 1.5 months during spring (March–April), using intact sediment in a flow-through system under close to natural light conditions. Although significant effects from temperature were observed during the entire experimental period, many were rather moderate and probably a combination of both direct and indirect effects. With the exception of an earlier development of floating microalgal mats at raised temperature, dividing the autotrophic compartment into a benthic and pelagic part, autotrophic variables, such as oxygen production, biomass, and species composition of benthic microalgae did not respond to warming. However, uptake of nutrients did increase, strengthening the role of shallow-water sediments as sinks for inorganic nutrients in spring. As hypothesized, heterotrophic variables (bacterial production, meiofaunal biomass, and dark fluxes of oxygen and total alkalinity) responded more clearly to warming than did autotrophic variables. Warming is generally hypothesized to push ecosystems towards heterotrophy, but there was no support for this in the present study. Although community respiration and anaerobic mineralization increased, the system remained highly autotrophic during the entire experiment due to the photosynthetic activity of benthic microalgae. The presence of a well-developed benthic microalgal community, already in early spring, appeared to moderate the temperature response. It therefore seems that, in spring, benthic microalgae dampen ecological consequences of global warming in illuminated sediment systems by maintaining the system net autotrophic.
|
|
| 6. |
- Brandsma, J, et al.
(författare)
-
A multi-proxy study of anaerobic ammonium oxidation in marine sediments of the Gullmar Fjord, Sweden
- 2011
-
Ingår i: ENVIRONMENTAL MICROBIOLOGY REPORTS. - : Wiley. - 1758-2229. ; 3:3, s. 360-366
-
Tidskriftsartikel (refereegranskat)abstract
- Anaerobic ammonium oxidation (anammox) is an important process for nitrogen removal in marine pelagic and benthic environments and represents a major sink in the global nitrogen cycle. We applied a suite of complementary methods for the detection and enumeration of anammox activity and anammox bacteria in marine sediments of the Gullmar Fjord, and compared the results obtained with each technique. 15N labelling experiments showed that nitrogen removal through N2 production was essentially limited to the upper 2 cm of the sediment, where anammox contributed 23–47% of the total production. The presence of marine anammox bacteria belonging to the genus ‘Candidatus Scalindua’ was shown by 16S rRNA gene sequence comparison. FISH counts of anammox bacteria correlated well with anammox activity, while quantitative PCR may have underestimated the number of anammox bacterial 16S rRNA gene copies at this site. Potential nitrogen conversion by anammox ranged from 0.6 to 4.8 fmol N cell−1 day−1, in agreement with previous measurements in the marine environment and in bioreactors. Finally, intact ladderane glycerophospholipid concentrations better reflected anammox activity and abundance than ladderane core lipid concentrations, most likely because the core lipid fraction contained a substantial fossil component, especially deeper in the sediment.
|
|
| 7. |
- Caradec, S., et al.
(författare)
-
Macrofaunal reworking activities and hydrocarbon redistribution in an experimental sediment system
- 2004
-
Ingår i: Journal of Sea Research. - : Elsevier BV. - 1385-1101. ; 52:3, s. 199-210
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of macrofaunal reworking activities on the redistribution of particle associated hydrocarbon compounds (HC) was experimentally investigated. Two distinct hydrocarbon mixtures adsorbed on montmorillonite particles (< 4 gm diameter) were added to the surface and deeper (2.5 cm) sediment layers. For comparison, luminophores (100-160 mum diameter) were added in the two deposit layers. At the start of the experiment, four macrobenthic species (the bivalve Abra nitida, the polychaete Scalibregma inflatum, and the echmoderms Amphiura filiformis and Echinocardium cordatum) were added to the sediment surface. The macrofauna added rapidly transferred HC from the surface sediment down to similar to5 cm depth by both continuous (biodiffusion) and non-continuous (biotransport) transport. Hydrocarbon compounds initially added to the deeper sediment layer were only subject to biodiffusion-like transport. Apparent biodiffusion coefficients (Db) quantified by using a 1-D model were between 0.5 and 8.4 x 10(-3) cm(2) d(-1), and biotransport coefficients (r) ranged from 2.0 to 27.6 X 10(-3) d(-1). Thus, the four species studied did not have the same effect on particle redistribution and, consequently, on HC repartition in the sediments. E. cordatum was the most efficient reworker. The present study demonstrated the importance of particle size selectivity by benthic fauna, and verified that macrofaunal reworking activities may redeposit sediment from deeper sediment layers on the sediment surface. Both processes have obvious implications for rates and pathways during organic matter mineralisation in marine sediments. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 8. |
|
|
| 9. |
- Dedieu, K, et al.
(författare)
-
Coupling of carbon, nitrogen and oxygen cycles in sediments from a Mediterranean lagoon: a seasonal perspective
- 2007
-
Ingår i: Marine ecology progress series. - 0171-8630. ; 346, s. 45-59
-
Tidskriftsartikel (refereegranskat)abstract
- Experimental data and simulations were used to investigate the seasonal coupling between carbon, nitrogen and oxygen cycles in marine sediments from a eutrophic shallow lagoon in the Mediterranean Sea area. A negative seasonal correlation was observed between oxygen consumption and coupled nitrification–denitrification rates in surface sediments. Elevated values of oxygen consumption rates were reached during warm periods (up to 87.7 mmol m–2 d–1) whereas nitrification and denitrification rates remained close to the lowest rates reported for coastal sediments (values around 0.021 to 0.35 mmol N m–2 d–1 for nitrification and 0.014 to 0.045 mmol N m–2 d–1 for denitrification). A steady-state diagenetic model closely represented the seasonal negative correlation of oxygen uptake, coupled nitrification–denitrification rates, the vertical distribution patterns of pore water oxygen and the solid phase distribution of organic carbon when nitrification inhibition by sulfide was included. Simulation adjusted to field data also highlighted the importance of oxygen penetration depth in the seasonal variation of nitrification. The modelling indicated that anaerobic metabolism was the most significant pathway (65 to 80%) during organic matter mineralization with a clear seasonal increase during warm periods. These warm periods were also characterized by the higher benthic demand of oxygen mostly used to re-oxidize the by-products from anaerobic reactions (from 57 to 82%), the other part being used for carbon mineralization.
|
|
| 10. |
- Eilola, Kari, et al.
(författare)
-
SMHI reportsSMHI rep., Oceanogr : Swedish Meteorological and Hydrological Institute reports. OceanographySMHISMHI report. Oceanography 2007:37OceanographyROSMHI RO
- 2017
-
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.
|
|
| 11. |
- Engelsen, Anna, 1964, et al.
(författare)
-
Benthic trophic status and nutrient fluxes in shallow-water sediments
- 2008
-
Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 78:4, s. 783-795
-
Tidskriftsartikel (refereegranskat)abstract
- Proliferation of fast-growing ephemeral macroalgae in shallow-water embayments constitutes a large-scale environmental change of coastal marine ecosystems. Since inorganic nutrients essential for the initiation and maintenance of macroalgal growth may be supplied from the underlying sediment, we investigated the coupling between benthic inorganic nutrient (mainly N and P) fluxes and sediment properties in 6 bays representing a wide gradient of sediment characteristics (grain size, organic matter content, solid phase C and N). The initial characterization of bays was made in June and also included measurements of oxygen flux and microphytobenthic and macrofaunal biomass. In September, still within the growth season of the macroalgae, complementary experiments with sediment-water incubations for benthic flux measurements of oxygen and nutrients focused on trophic status (balance between auto- and heterotrophy) as a controlling factor for rates of measured benthic nutrient fluxes. Generally, sediments rendered autotrophic by microphytobenthic photosynthesis removed nutrients from the overlying water, while heterotrophic sediments supplied nutrients to the overlying bottom water. Estimations of the green-algal nutrient demand suggested that late in the growth season, net heterotrophic sediments could cover 20% of the N-demand and 70% of the P demand. As the benthic trophic status is a functional variable more closely coupled to nutrient fluxes than the comparably conservative structural parameter organic matter content, we suggest that the trophic status is a more viable parameter to classify sediments and predict benthic nutrient fluxes in shallow-water environments.
|
|
| 12. |
- Engelsen, Anna, 1964, et al.
(författare)
-
Links Between Bottom-Water Anoxia, the Polychaete Nereis diversicolor, and the Growth of Green-Algal Mats
- 2010
-
Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 33:6, s. 1365-1376
-
Tidskriftsartikel (refereegranskat)abstract
- Sediment-water incubations were used to study effects of episodic anoxia on filamentous Ulva sp. Treatments included undisturbed sediment with (AnoxSed) and without (NatSed) exposure to 5 days of anoxia, and cores with only the top 0.5 cm of sediment (SurfSed; no macrofauna, restricted pore-water nutrient pool). All three treatments contained Ulva propagules. An Ulva mat developed in the SurfSed, and after the anoxic period in the AnoxSed cores. No growth was observed in the NatSed treatment. In the AnoxSed, Ulva was progressively removed upon reoxygenation through grazing by Nereis. The results suggest that episodic anoxia stimulates the growth of macroalgal mats not only by increasing the availability of nutrients from the sediment, but also by reducing macrofaunal grazing pressure. Infauna (grazing and bioturbation), benthic microalgae (nutrient competition and retention), and pore-water nutrients appear key components in a biogeochemical network with complex feedbacks controlling the growth of green-algal mats in shallow-water systems.
|
|
| 13. |
- Engström, Pia, 1970, et al.
(författare)
-
Anaerobic ammonium oxidation by nitrite (anammox): Implications for N-2 production in coastal marine sediments
- 2005
-
Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 69:8, s. 2057-2065
-
Tidskriftsartikel (refereegranskat)abstract
- The respiratory reduction of nitrate (denitrification) is acknowledged as the most important process that converts biologically available nitrogen to gaseous dinitrogen (N-2) in marine ecosystems. Recent findings, however, indicate that anaerobic ammonium oxidation by nitrite (anammox) may be an important pathway for N-2 formation and N removal in coastal marine sediments and in anoxic water columns of the oceans. In the present study, we explored this novel mechanism during N mineralization by 15 N amendments (single and coupled additions of (NH4+)-N-15, (NO3-)-N-14 and (NO3-)-N-15) to surface sediments with a wide range of characteristics and overall reactivity. Patterns of N-29/30(2) production in the pore water during closed sediment incubations demonstrated anammox at all 7 of the investigated sites. Stoichiometric calculations revealed that 4% to 79% of total N-2 production was due to this novel route. The relative importance of anammox for N2 release was inversely correlated with remineralized solute production, benthic O-2 consumption, and surface sediment Ch1 a. The observed correlations indicate competition between reductants for pore water nitrite during early diagenesis and that additional factors (e.g. availability of Mn-oxides), superimposed on overall patterns of diagenetic activity, are important for determining absolute and relative rates of anammox in coastal marine sediments. Copyright (c) 2005 Elsevier Ltd
|
|
| 14. |
|
|
| 15. |
- Gilbert, F., et al.
(författare)
-
2-D optical quantification of particle reworking activities in marine surface sediments
- 2003
-
Ingår i: JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY. - 0022-0981. ; 285, s. 251-263
-
Tidskriftsartikel (refereegranskat)abstract
- Particle and solute transport by faunal activities may significantly influence rates and pathways of organic matter mineralization during early diagenesis in surface sediments. One of the most frequently utilized techniques to quantify benthic biological reworking activities involves the calculation of a biodiffusion coefficient (D-b) estimated from model predictions of 1-D tracer distribution patterns. This technique is labor-intensive and time-demanding. Furthermore, it is normally used for measurements over several days and averages overall transport mechanisms from 3-D to 1-D on a cm scale. In the frame of this work, we developed a new technique based on the nondestructive screening of fluorescent particles (luminophores) using optical discrimination and CCD camera detection of fluorescence (2-D). At a site characterized by a dense population of the brittle star Amphiura filiformis and a high biodiffusion coefficient (obtained from 1-D distributions; D-b = 3 5.5 +/- 3.7 cm(-2) year(-1); n = 3), the optical reworking coefficient (ORC), estimated from the 2-D luminophore distribution patterns, was calculated (ORC = 27.4 +/- 9.1 DeltaQ cm(-2) h(-1); n=24). A nondestructive 2-D approach to quantify particle reworking may provide a powerful and complementary tool to further understand particle transport by the benthic fauna in surface sediments. The optical technique for 2-D detection of luminophores is relatively fast and easy to perform, with the ability to detect small scale (mm) particle movements on a time resolution of minutes or less. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
- Gilbert, F., et al.
(författare)
-
Redox oscillation and benthic nitrogen mineralization within burrowed sediments: An experimental simulation at low frequency
- 2016
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 482, s. 75-84
-
Tidskriftsartikel (refereegranskat)abstract
- Possible effects of sediment ventilation by benthic organisms on the nitrogen cycle were investigated using an experimental setup that mimicked stable or relatively low frequency oscillating redox conditions potentially found in bioturbated deposits. Three different conditions inside burrowed sediments were simulated using 2 mm thick sediment layers: 1) continuously oxic sediment exposed to oxygenated overlying bottom water (e.g., burrow walls, surface sediment), 2) continuously anoxic sediment out of reach from either O-2 or NO3- diffusion and 3) the lining/boundary of burrow structures or sediment pockets (e.g., excavated during feeding) subject to intermittent irrigation and redox fluctuations over several day timescales. Results demonstrated that intermittent redox fluctuations allowed sustained denitrification and episodic nitrification, whereas significant denitrification and both nitrification and denitrification were absent after similar to 5-10 days from continuously oxidized and anoxic zones respectively. Intermittent redox oscillations enhance metabolic diversity, magnify loss of dissolved inorganic N to solution, and permit sustained coupling between ammonification, nitrification, and denitrification despite lack of a stable stratified oxic-anoxic redox structure. Even relatively low frequency redox oscillations induce greater N loss compared to sediment that is continuously exposed to oxic and anoxic conditions.
|
|
| 20. |
- Gilbert, F., et al.
(författare)
-
Sediment reworking by marine benthic species from the Gullmar Fjord (Western Sweden): Importance of faunal biovolume
- 2007
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 348:1-2, s. 133-144
-
Tidskriftsartikel (refereegranskat)abstract
- In order to compare and quantify sediment reworking activities by different species/functional groups of macrofauna, a laboratory experiment was carried out with species from the Gullmarsfjord (Western Sweden). Monospecific communities of Amphiura filiformis, Echinocardium cordatum, Scalibregma inflatum and Abra nitida were introduced in experimental mesocosms, with identical densities (795 ind. m(-2)), for 10 days. Sediment reworking was studied by quantifying downward and upward movements of fluorescent inert tracers (luminophores). Luminophores with different colour were initially deposited both at the sediment surface and within the sediments. Population biomass and biovolume were also determined. Surface tracers reworking coefficients ranged from 0.6 to 2.2 cm(2) y(-1) and 0.9 to 4.1 y(-1), respectively for the biodiffusive-like and non-local transports. Calculated biodiffusive-like coefficient was between 1.0 and 2.3 cm(2) y(-1) for the deep tracers. For both tracers, the E. cordatum population presented the highest reworking coefficients. Among the morphological and/or ethological parameters that could determine overall patterns of reworking and differences between species, results have shown a direct relationship between the apparent biodiffusive mixing and the biovolume of the individuals (D-b=0.35 * Biovolume). This suggests that the biovolume-of macrofauna may allow a rough estimate of the biodiffusive-like reworking intensity of particles deposited on the sediment surface. (c) 2007 Elsevier B.V. All rights reserved.
|
|
| 21. |
- Gilbert, F., et al.
(författare)
-
Sediment reworking by the burrowing polychaete Hediste diversicolor modulated by environmental and biological factors across the temperate North Atlantic. A tribute to Gaston Desrosiers
- 2021
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 541
-
Tidskriftsartikel (refereegranskat)abstract
- Particle mixing and irrigation of the seabed by benthic fauna (bioturbation) have major impacts on ecosystem functions such as remineralization of organic matter and sediment-water exchange. As a tribute to Prof. Gaston Desrosiers by the Nereis Park association, eighteen laboratories carried out a collaborative experiment to acquire a global snapshot of particle reworking by the polychaete Hediste diversicolor at 16 sites surrounding the Northern Atlantic. Organisms and soft sediments were collected during May - July at different geographical locations and, using a common laboratory protocol, particulate fluorescent tracers (`luminophores') were used to quantify particle transport over a 10-day period. Particle mixing was quantified using the maximum penetration depth of tracers (MPD), particle diffusive coefficients (D-b), and non-local transport coefficients (r). Non-local coefficients (reflecting centimeter scale transport steps) ranged from 0.4 to 15 yr(-1), and were not correlated across sites with any measured biological (biomass, biovolume) or environmental parameters (temperature, grain size, organic matter). Maximum penetration depths (MPD) averaged similar to 10.7 cm (6.5-14.5 cm), and were similar to the global average bioturbation depth inferred from short-lived radiochemical tracers. MPD was also not correlated with measures of size (individual biomass), but increased with grain size and decreased with temperature. Bio-diffusion (D-b) correlated inversely with individual biomass (size) and directly with temperature over the environmental range (Q(10) similar to 1.7; 5-21 degrees C). The transport data were comparable in magnitude to rates reported for localized H. diversicolor populations of similar size, and confirmed some but not all correlations between sediment reworking and biological and environmental variables found in previous studies. The results imply that measures of particle reworking activities of a species from a single location can be generally extrapolated to different populations at similar conditions.
|
|
| 22. |
|
|
| 23. |
- Hakonen, Aron, 1970, et al.
(författare)
-
A DHPDS-based fluorosensor for high-precision measurements of pH in the pH interval 6-9
- 2010
-
Ingår i: Talanta. - 0039-9140. ; 80:5, s. 1964-1969
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents a high-performance ratiometric pH optode based on the fluorophore 6,8-dihydroxypyrene-1,3-disulfonic acid (DHPDS). The two pH-sensitive terminal hydroxy groups of DHPDS facilitated dual excitation/dual emission (F1: λ1,ex = 420 nm, λ1,em = 462 nm; F2: λ2,ex = 470 nm, λ2,em = 498 nm) properties for ratiometric (RF1,F2 = F1/F2) normalization of sensor signal. The sensor demonstrated an exponentially decreasing ratiometric response with increasing pH, with a linear correlation (R2 = 0.9936) between 10log(RF1,F2) and pH within the pH interval 6–9. Precision determined as the IUPAC pooled standard deviation for the pH values 6.00, 7.01 and 9.01, was 0.0057 pH units for the fluorosensor and 0.0054 for a commercially available pH electrode used for comparison. Between the end-points of calibration at pH 7.01, the precision of the sensor was 0.0037 pH units. Effects from changes in ionic strength (Itot, 10–700 mM) were more pronounced for the electrode, with a linear (R2 = 0.9976) increase in response (δE/δpH) with increasing Itot. The DHPDS-based fluorosensor, however, retained sensitivity (δ10log(RF1,F2)/δpH = 0.8024 ± 0.0145), though with an overall increase in ratiometric signal with increasing Itot. The preserved sensitivity despite changes in ionic strength was possibly a consequence from the dual photo-acidic properties of DHPDS. Analytical characteristics of immobilized DHPDS therefore not only facilitated high-performance measurements over a wide pH range, but also opened for straightforward simultaneous measurements of pH and ionic strength.
|
|
| 24. |
- Hakonen, Aron, 1970, et al.
(författare)
-
A high-precision ratiometric fluorosensor for pH: Implementing time-dependent non-linear calibration protocols for drift compensation
- 2007
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 606:1, s. 63-71
-
Tidskriftsartikel (refereegranskat)abstract
- We present a versatile time-dependent non-linear calibration protocol for optical sensors, implemented on the pH sensitive ratiometric fluorophore 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) immobilized in ethyl-cellulose. The calibration protocol individually compensated for the progressive drift of calibration parameters, whereby sensor precision and accuracy, as well as applicable lifetime were improved. A severely reduced photoacidity was observed for the immobilized fluorophore, for which excited state dynamics was characterized and benefited from during measurements. Due to the significantly reduced photoacidity of HPTS immobilized in the ethyl-cellulose sensing membrane, a dual excitation/dual emission (F1, ex/em: 405/440 nm and F2, ex/em: 465/510 nm) ratiometric (RF1,F2 = F1/F2) sensing scheme could be used to amplify sensor response. The signal to noise (S/N) ratio was enhanced by 400% utilizing the dual excitation/dual emission ratiometric sensing scheme, rather than the more commonly used protocol of dual excitation/single emission for HPTS fluorescence. Apparent pKa of the fluorophore ranged from 6.74 to 8.50, mainly determined by the immobilization procedure. The repeatability (IUPAC, pooled standard deviation) over three pH values (6.986, 7.702 and 7.828) was 0.0044 pH units for the optical sensor, compared to 0.0046 for the electrode used for standardization. Sensor analytical characteristics were thereby in principle limited by the performance of the standardization procedure.
|
|
| 25. |
- Hakonen, Aron, 1970, et al.
(författare)
-
A potential tool for high-resolution monitoring of ocean acidification.
- 2013
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 786, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acid-ification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and lowoceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck forresearch on ocean acidification is long-term monitoring and the collection of consistent high-resolutionpH measurements. This study presents a low-power (<1 W) small sample volume (25l) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatialresolution (approximately 15 s and 100 m between samples). A 405 nm light emitting diode and the blueand green channels from a digital camera was used for swift detection of fluorescence from the pH sen-sitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated byautomated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegatregion with a large range in salinity (∼3–30) and temperature (∼0–25◦C). Ship-board precision of salinityand temperature adjusted pH measurements were estimated as low as 0.0001 pH units.
|
|
| 26. |
- Hakonen, Aron, 1970, et al.
(författare)
-
Analytical performance during ratiometric long-term imaging of pH in bioturbated sediments
- 2010
-
Ingår i: Talanta. - : Elsevier BV. - 0039-9140. ; 81:4-5, s. 1393-1401
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the long-term analytical performance of a high-resolution ratiometric imaging sensor for pH was quantitatively determined The sensor was applied in an experimental microcosm to Illustrate biogeochemical consequences from mining activities by the chemosymbiotic bivalve Thyasira sarsi. Utilizing time-correlated pixel-by-pixel calibration protocols during imaging, close 10 90% of the pixels were associated with a precision (S D) of <0.05 pH units at the end of an experimental period of 17 days For comparison, a precision of <0 05 pH units was achieved for less than 50% of the pixels throughout experiments using conventional pre-sample calibration procedures. The average standard deviation of pixels was 001 pH units. Image analysis of single pixel derivatives and pH measurements over time suggested that T. sarsi affect pH distributions and general sediment geochemistry more than would be expected based on the small size of the bivalves. A significant decrease of pH in the overlying water suggested a considerable release of reduced compounds from the exhalent stream of the thyasirids. Strong pH gradients were demonstrated not only across the sediment-water interface but, also associated with bioturbation activities immediately adjacent to T. sarsi burrowing tracts, inhalant tubes and pedal tracts in the sediment maim. Gradients of up to 1 16 pH units per mm were observed. (C) 2010 Elsevier B V All rights reserved
|
|
| 27. |
- Hakonen, Aron, 1970, et al.
(författare)
-
Applications of imaging optodes
- 2007
-
Ingår i: Pittsburg Conference on Analytical Chemistry (PITTCON).
-
Konferensbidrag (refereegranskat)
|
|
| 28. |
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Hulth, Stefan, 1965, et al.
(författare)
-
Nitrogen removal in marine environments: recent findings and future research challenges
- 2005
-
Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 94:1-4, s. 125-145
-
Tidskriftsartikel (refereegranskat)abstract
- Respiratory reduction of nitrate (denitrification) is recognized as the most important process converting biologically available (fixed) nitrogen to N-2. In current N cycle models, a major proportion of global marine denitrification (50-70%) is assumed to take place on the sea floor, particularly in organic rich continental margin sediments. Recent observations indicate that present conceptual views of denitrification and pathways of nitrate reduction and N, formation are incomplete. Alternative N cycle pathways, particularly in sediments. include anaerobic ammonium oxidation to nitrite, nitrate and N-2 by Mn-oxides, and anaerobic ammonium oxidation coupled to nitrite reduction and subsequent N, mobilization. The discovery of new links and feedback mechanisms between the redox cycles of, e.g., C, N, S, Mn and Fe casts doubt on the present general understanding of the global N cycle. Recent models of the oceanic N budget indicate that total inputs are significantly smaller than estimated fixed N removal. The occurrence of alternative N reaction pathways further exacerbates the apparent imbalance as they introduce additional routes of N removal. In this contribution, we give a brief historical background of the conceptual understanding of N cycling in marine ecosystems, emphasizing pathways of aerobic and anaerobic N mineralization in marine sediments, and the implications of recently recognized metabolic pathways for N removal in marine environments. (c) 2004 Elsevier B.V. All rights reserved.
|
|
| 35. |
|
|
| 36. |
- Karlson, K., et al.
(författare)
-
Density of Monoporeia affinis and biogeochemistry in Baltic Sea sediments
- 2007
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 344:2, s. 123-135
-
Tidskriftsartikel (refereegranskat)abstract
- This study fccused on effects from Monoporeia affinis reworking and ventilation activities on benthic fluxes and mineralization processes during a simulated bloom event. The importance of M. affinis density for benthic solute (O-2, Sigma NO2- +NO3-, NH4+ HPO42-) fluxes and sediment reactivity (mobilization of NH4+ and H 4 following additions of organic material to the sediment surface was experimentally investigated using sediment-water and closed sediment Oar) incubations. Three different densities of M affinis were used to resemble a low, medium and high density situation (1300, 2500 and 6400 ind. m(-2), respectively) of a natural amphipod community. The degradation of phytodetritus (Tetraselmis sp., 5 g C m(-2)) added to the sediment surface was followed over a period of 20 days. Benthic solute fluxes of O-2, Sigma NO2- +NO3- and NH4+ were generally progressively stimulated with increasing number of M. affinis, while no such correlation was found for HPO42-. Solute fluxes were initially enhanced 1 to 2 days after the addition of phytodetritius, caused by mineralization of the most labile organic material and a food-stimulated irrigation by the amphipods. There was no effect from the activity of M. affinis on total denitrification (Dtot=Dn+Dw) or denitrification utilizing nitrate from coupled nitrification/denitrification (Dn) for any of the densities examined. Denitrification utilizing overlying water nitrate (Dw) was only about 10% of Dtot. Dw was significantly enhanced for the highest M affinis density investigated. The reactivity of the sediment decreased progressively with increasing density of M affinis and with time of the experiment. However, enhanced ammonium production at least 6 days after the organic addition indicated excretion of N-containing organic compounds by M affinis. In conclusion, large spatial and temporal variations in density of M affinis may be of significant importance for benthic solute fluxes and overall mineralization of organic material in Baltic Sea sediments. (C) 2007 Elsevier B.V. All rights reserved.
|
|
| 37. |
- Karlson, Karin, 1961, et al.
(författare)
-
Experimental recolonisation of Baltic Sea reduced sediments: survival of benthic macrofauna and effects on nutrient cycling
- 2005
-
Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 294, s. 35-49
-
Tidskriftsartikel (refereegranskat)abstract
- A recolonisation experiment was performed in vitro on highly reduced laminated Baltic Sea sediments initially devoid of larger benthic fauna. The survival capacity of 3 common benthic species Monoporeia affinis, Macoma balthica and Marenzelleria viridis was investigated along with overall effects of bioturbation and bioirrigation on benthic reaction and transport processes. Benthic fluxes of oxygen and nutrients, sediment denitrification and nutrients in the porewater were measured. Survival of M. affinis increased with time and sediment reworking, while no such feedback was observed for M balthica and M. viridis, Macrofaunal irrigation and bioturbating activities significantly enhanced solute fluxes in the manipulated cores compared to the control. Mass balance calculations indicated that net N-mineralisation in the manipulated cores was stimulated by 1 to 2 orders of magnitude compared to the control. Despite relatively high nitrate fluxes from the overlying water to the sediment (similar to 1 mmol m(-2) d(-1)), measured rates Of total denitrification were in general low (20 to 45 mu mol N-2 m(-2) d(-1)) in all cores. Denitrification, using nitrate supplied from the overlying water (D-w), was similar to coupled nitrification/denitrification (D-n), although D-w was significantly higher than D-n in the M. affinis cores. In conjunction with high nitrate fluxes into the sediment and high ammonium fluxes to the overlying water, the generally low denitrification rates indicated dissimilatory nitrate reduction to ammonium (DNRA) as the main pathway for nitrate removal. Thus, the main source of bottom water ammonium was overlying water nitrate, rather than ammonium produced in surface sediments during mineralisation of organic N.
|
|
| 38. |
- Karlsson, Roger, 1975, et al.
(författare)
-
Identification of key proteins involved in the anammox reaction
- 2009
-
Ingår i: FEMS microbiology letters. - : Oxford University Press (OUP). - 1574-6968 .- 0378-1097. ; 297:1, s. 87-94
-
Tidskriftsartikel (refereegranskat)abstract
- Bacteria performing anaerobic ammonium oxidation (anammox) are key players in the global nitrogen cycle due to their inherent ability to convert biologically available nitrogen to N(2). Anammox is increasingly being exploited during wastewater treatment worldwide, and about 50% of the total N(2) production in marine environments is estimated to proceed by the anammox pathway. To fully understand the microbial functionality and mechanisms that control environmental feedbacks of the anammox reaction, key proteins involved in the reaction must be identified. In this study we have utilized an analytical protocol that facilitates detection of proteins associated with the anammoxosome, an intracellular membrane compartment within the anammox bacterium. The protocol enabled us to identify several key proteins of the anammox reaction including a hydrazine hydrolase producing hydrazine, a hydrazine-oxidizing enzyme converting hydrazine to N(2) and a membrane-bound ATP synthase generating ATP from the gradients of protons formed in the anammox reaction. We also performed immunogold labelling electron microscopy to determine the subcellular location of the hydrazine hydrolase. The results from our study support the hypothesis that proteins associated with the anammoxosome host the complete suite of reactions during anammox.
|
|
| 39. |
- Karlsson, R., et al.
(författare)
-
Proteotyping: Proteomic characterization, classification and identification of microorganisms - A prospectus
- 2015
-
Ingår i: Systematic and Applied Microbiology. - : Elsevier BV. - 0723-2020. ; 38:4, s. 246-257
-
Forskningsöversikt (refereegranskat)abstract
- Modern microbial systematics requires a range of methodologies for the comprehensive characterization, classification and identification of microorganisms. While whole-genome sequences provide the ultimate reference for defining microbial phylogeny and taxonomy, selected biomarker-based strategies continue to provide the means for the bulk of microbial systematic studies. Proteomics, the study of the expression of genes, as well as the structure and function of the resulting proteins, offers indirect measures of genome sequence data. Recent developments in applications of proteomics for analyzing microorganisms have paralleled the growing microbial genome sequence database, as well as the evolution of mass spectrometry (MS) instrumentation and bioinformatics. MALDI-TOF MS, which generates proteomic mass patterns for 'fingerprint'-based characterizations, has provided a marked breakthrough for microbial identification. However, MALDI-TOF MS is limited in the number of targets that can be detected for strain characterization. Advanced methods of tandem mass spectrometry, in which proteins and peptides generated from proteins, are characterized and identified, using LC-MS/MS, provide the ability to detect hundreds or thousands of expressed microbial strain markers for high-resolution characterizations and identifications. Model studies demonstrate the application of proteomics-based analyses for bacterial species- and strain-level detection and identification and for characterization of environmentally relevant, metabolically diverse bacteria. Proteomics-based approaches represent an emerging complement to traditional methods of characterizing microorganisms, enabling the elucidation of the expressed biomarkers of genome sequence information, which can be applied to 'proteotyping' applications of microorganisms at all taxonomic levels. (C) 2015 Elsevier GmbH. All rights reserved.
|
|
| 40. |
- Karlsson, R., et al.
(författare)
-
Subcellular localization of an ATPase in anammox bacteria using proteomics and immunogold electron microscopy
- 2014
-
Ingår i: Fems Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097. ; 354:1, s. 10-18
-
Tidskriftsartikel (refereegranskat)abstract
- Anaerobic ammonium oxidation (anammox) has received significant attention during optimization of waste-water treatment and constitutes an important pathway for the removal of bioavailable nitrogen from natural environments. Studies of key catabolic enzymes indicate that the anammox reaction takes place inside the anammoxosome, an organelle-like membranous compartment of anammox bacteria. The anammoxosome has also been suggested as a site for ATP synthesis. A lipid-based protein immobilization technique, previously used to identify proteins essential for the anammox reaction, was in this study used to select linear epitopes for antibodies specifically targeted against an identified ATPase. The approach of using proteomics and bioinformatics as tools for selecting antibody targets for immunolocalization provides an important alternative to traditional methods for selection of specific antibodies. Immunogold electron microscopy and statistical evaluations indicated that the antibodies against the ATPase were exclusively found associated with the anammoxosome membrane. This provides strong evidence for ATP synthesis by an intracellular proton motive force in anammox bacteria. Within prokaryotes, an ATP synthase associated with an intracellular compartment is a feature unique for anammox bacteria.
|
|
| 41. |
- Lindqvist, Stina, 1981, et al.
(författare)
-
Activities by Hediste diversicolor under different light regimes: Experimental quantification of particle reworking using time-resolved imaging
- 2013
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 448, s. 240-249
-
Tidskriftsartikel (refereegranskat)abstract
- Particle reworking by the ragworm Hediste diversicolor was assessed by quantifying the transport of fluorescent particles (luminophores) added to the surface sediment during a 10 day experiment. Plexiglass cores and thin glass aquaria with fauna and controls were exposed to either 12 hour light/dark cycles or constant darkness. Luminophore distributions were evaluated by side-view imaging of the aquaria together with destructive sectioning and quantification of tracer distributions in both types of microcosms at the end of experiments. Tracer distributions were evaluated by the gallery-diffusor model, from which the biodiffusion (Db) and the non-local transport (r) coefficients were determined. In addition, the maximum penetration depth (MPD) of luminophores, the 2-D redistribution coefficient, and the transport rate were used as a suite of proxies to quantify particle reworking by fauna. All measured reworking proxies demonstrated a general decrease in transport of luminophores in darkness compared to light/dark cycles. The difference was significant for proxies determined from sectioning. Imaging of particle transport demonstrated that rates were ~ 30% higher during light/dark cycles, with ~ constant amount of particles transported on a daily basis. The effect of light was consistent in the two microcosm types. However, there was a significant difference in Db, while r and MPD were not significantly different between the cores and aquaria. Overall, these results suggest a light-triggered surface feeding by H. diversicolor. Our study highlights the importance of experimental settings for quantification of particle transport by fauna, and that light conditions and types of experimental microcosms need to be carefully considered during investigations of bioturbation in illuminated environments.
|
|
| 42. |
- Lindqvist, Stina, 1981, et al.
(författare)
-
Biogeochemistry in highly reduced mussel farm sediments during macrofaunal recolonization by Amphiura filiformis and Nephtys sp.
- 2009
-
Ingår i: Marine environmental research. - : Elsevier BV. - 0141-1136. ; 67:3, s. 136-45
-
Tidskriftsartikel (refereegranskat)abstract
- Mussel farming is considered a viable means for reducing coastal eutrophication. This study assessed the importance of bioturbation by recolonizing fauna for benthic solute fluxes and porewater distributions in manipulated mussel farm sediments. Three consecutive time-series flux incubations were performed during an experimental period of three weeks in sieved farm sediment treated with the brittle star Amphiura filiformis and the polychaete Nephtys sp. The functional behavior of Nephtys sp. and interactions between Nephtys sp. and the spontaneously colonizing spionid Malacoceros fuliginosus determined the biogeochemical response in the Nephtys sp. treatment. For example, the oxic zone was restricted and benthic nitrate and silicate fluxes were reduced compared to the brittle star treatment. A. filiformis seemed to enhance the bioadvective solute transport, although an increased supply of oxygen was due to the highly reducing conditions of the sediment mainly seen as secondary effects related to porewater distributions and benthic nutrient fluxes.
|
|
| 43. |
|
|
| 44. |
- Norling, K., et al.
(författare)
-
Importance of functional biodiversity and species-specific traits of benthic fauna for ecosystem functions in marine sediment
- 2007
-
Ingår i: Marine Ecology-Progress Series. ; 332, s. 11-23
-
Tidskriftsartikel (refereegranskat)abstract
- Fauna have been found to regulate important biogeochemical properties and ecosystem functions in benthic environments. In this study, we focused on how functional biodiversity and species-specific traits of benthic macrofauna affect key ecosystem functions related to organic matter mineralization and cycling of nutrients in surface sediments. Dominant benthic invertebrates from the Baltic Sea and the Skagerrak were classified into functional groups in accordance with their behaviour, feeding and sediment reworking activities. Macrofauna species were added in different combinations to defaunated Baltic sediments in 2 parallel microcosm systems fuelled with brackish and marine water. In total, there were 12 treatments that differed in terms of functional diversity of benthic fauna. The experiments demonstrated that faunal activities directly affected benthic oxygen and nutrient fluxes, sediment reactivity and pore-water distribution under both Baltic and Skagerrak conditions. Benthic fluxes, sediment reactivity and pore-water distribution were similar in Baltic and Skagerrak treatments, in which the same functional biodiversity and species-specific traits of benthic macrofauna were observed. Although no significant effects of functional biodiversity could be detected under Baltic or Skagerrak conditions, treatments with bioturbating fauna from the Skagerrak enhanced oxygen consumption and nutrient fluxes compared to treatments with Baltic fauna and Skagerrak fauna with functional groups similar (parallel) to the Baltic fauna. Moreover, speciesspecific traits related to the Skagerrak fauna (e.g. the thalassinid shrimp Calocarls macandreae) exceeded the effects of all other faunal treatments. This suggests that species-specific traits of macrofauna may override species richness and functional biodiversity of macrofauna when regulating important ecosystem properties and functions in benthic environments.
|
|
| 45. |
- Schmid, M. C., et al.
(författare)
-
Anaerobic ammonium-oxidizing bacteria in marine environments: widespread occurrence but low diversity
- 2007
-
Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 9:6, s. 1476-1484
-
Tidskriftsartikel (refereegranskat)abstract
- Laboratory and field studies have indicated that anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. In this study 11 additional anoxic marine sediment and water column samples were studied to substantiate this claim. In a combined approach using the molecular methods, polymerase chain reaction (PCR), qualitative and quantitative fluorescence in situ hybridization (FISH), as well as N-15 stable isotope activity measurements, it was shown that anammox bacteria were present and active in all samples investigated. The anammox activity measured in the sediment samples ranged from 0.08 fmol cell(-1) day(-1) N-2 in the Golfo Dulce (Pacific Ocean, Costa Rica) sediment to 0.98 fmol cell(-1) day(-1) N-2 in the Gullmarsfjorden (North Sea, Sweden) sediment. The percentage of anammox cell of the total population (stained with DAPI) as assessed by quantitative FISH was highest in the Barents Sea (9% +/- 4%) and in most of the samples well over 2%. Fluorescence in situ hybridization and phylogenetic analysis of the PCR products derived from the marine samples indicated the exclusive presence of members of the Candidatus 'Scalindua' genus. This study showed the ubiquitous presence of anammox bacteria in anoxic marine ecosystems, supporting previous observations on the importance of anammox for N cycling in marine environments.
|
|
| 46. |
- Strömberg, Niklas, 1974, et al.
(författare)
-
A fluorescence ratiometric detection scheme for ammonium ions based on the solvent sensitive dye MC 540
- 2003
-
Ingår i: Sensors and Actuators B-Chemical. ; 90:1-3, s. 308-318
-
Tidskriftsartikel (refereegranskat)abstract
- Principles of wavelength ratiometric evaluation of fluorescence have been extensively used to cancel out and reference sensor response not associated with the analyte. Main limitations of this technique include wavelength ratiometric properties inherent only to a restricted number of solute specific fluorescent dyes. This study presents a dual-excitation/dual-emission ratiometric detection scheme applied on a two-phase coextraction based fluorosensor. Rather than utilizing spectral shifts associated with various complexation and acid-base equilibria of solute specific indicators, we made use of the fluorescence shift induced by the phase transfer of the solvent sensitive dye merocyanine 540 (MC 540) upon ammonium-nonactin coextraction in a hydrogel-ether emulsion. The two-phase ratiometric fluorosensor was exposed to conditions frequently reported to alter performance of fluorescence based optical sensors. Sensor response was unaffected by O-2 concentrations, and signals caused by variations in excitation light intensity and pH were found more or less completely eliminated by the ratiometric procedure. Selectivity towards NH4+ and possible interferences from K+ were more accurately evaluated using the dual-excitation/dual-emission ratio, compared to a single-excitation/single-eniission fluorescence scheme. It was not possible to eliminate artifacts associated with fluctuations in temperature, effective MC 540 concentrations and sample ionic strength by the ratiometric reference scheme, most likely due to monomer-dimer complexation of the indicator dye and the formation of larger aggregates at concentrations exceeding the critical salt concentration of MC 540. Principles described for a two-phase ratiometric detection procedure associated with solvent sensitive dyes rather than solute specific fluorescent dyes may provide a powerful tool for direct solute detection. Thus, the limited versatility of wavelength ratiometric fluorescence detection to specially designed compounds with wavelength ratiometric properties directly linked to interactions with the analyte, may be overcome. (C) 2003 Elsevier Science B.V. All rights reserved.
|
|
| 47. |
- Strömberg, Niklas, 1974, et al.
(författare)
-
Ammonium selective fluorosensor based on the principles of coextraction
- 2001
-
Ingår i: Analytica Chimica Acta. ; 443:2, s. 215-225
-
Tidskriftsartikel (refereegranskat)abstract
- The overall objective of this study was to develop an optical fluorosensor (optode) for real-time measurements of ammonium concentrations in natural liquid samples. An NH4+ optode that can be used at such conditions should be analyte specific and independent of ionic strength and pH within a range normally found in such samples (pH 6-8; I-tot 0-700 mM). Additional desired sensor feature is a short response time (preferably minutes or less). This work presents an NH4+ fluorosensor that utilizes similar principles previously described for a K+ selective fluorosensor, i.e. coextraction of a nonactin- ammonium complex and a solvatochromic dye in a hydrogel-ether emulsion. The sensor was tested for its selectivity for ammonium ions compared to other solutes from which interferences frequently have been reported, e.g. K+ and H+. Furthermore, sensor performance at different ionic strengths (I) was evaluated. The ammonium fluorosensor was found to be (i) analyte specific with a selectivity coefficient (K- NH4+.K+(opt)) of 7 x 10(-2), i.e. sensor membranes are about twice as selective to ammonium relative potassium compared to previous studies of electrochemical sensors; (ii) pH independent within the interval 6.0-7.8; (iii) dependent on ionic strength within the interval 100-700 mM, with optimal performance at lowest I-tot evaluated (100 mm); (iv) has a response time of less than 4 min; (v) has the ability to reversibly sense NH4+ even at muM levels. Sensor dynamic range was estimated as 10 muM-100 mM NH4+ in a sample matrix with ionic strength of 100 mM. Construction, configuration and composition of sensor membranes make the ammonium fluorosensor several times reusable, with a sensor shelf life time of at least 8 months. (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 48. |
- Strömberg, Niklas, 1974, et al.
(författare)
-
Assessing an imaging ammonium sensor using time correlated pixel-by-pixel calibration
- 2005
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 550:1-2, s. 61-68
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a ratiometric imaging ammonium sensor (optode) and a novel calibration technique for imaging optodes were developed, tested and thoroughly evaluated. The overall sensing scheme is based on ammonium coextraction together with a solvent sensitive dye in a hydrogelether emulsion. Quantification of ammonium during 10 days of experiments was made through an image ratio (excitation:emission/excitation:emission; 572 nm:592 nm/520 nm:572 nm ) coupled to the calibration technique i.e. time correlated pixel-by-pixel calibration (TCPC). Sensor performance was validated according to International Union of Pure and Applied Chemistry (IUPAC) recommendations for within-laboratory requirements of reproducibility, and compared with the more frequently used approach of image pixel calibration. Using the TCPC protocol; a limit of detection (LOD) of 1.2 ± 0.2 × 10−6 M was calculated. The preliminary estimate of precision at 200 × 10−6 M, using relative standard deviation (R.S.D.) as a measure, was 5.2% over the 10-day period. The within-batch repeatability was 2.3% (R.S.D.) at 200 × 10−6 M. A linear fit of the data compared the drift over time for the various calibration techniques. Without time correlation, the ratiometric pixel-by-pixel calibrated signal drifted significantly over time. The drift was more or less completely removed using the TCPC protocol. The image resolution, experimentally determined at the distance applied (3 × 10−1 m) by the 1090% edge-response approach, was 210 × 10−6 m. Imaging concentrations and diffusive transport of ammonium in soil during dissolution of a fertilizer stick was given as an example of a versatile sensor application.
|
|
| 49. |
|
|
| 50. |
- Strömberg, Niklas, 1974, et al.
(författare)
-
Time correlated pixel-by-pixel calibration for quantification and signal quality control during solute imaging
- 2006
-
Ingår i: Sensors and Actuators B-Chemical. - : Elsevier BV. - 0925-4005. ; 115:1, s. 263-269
-
Tidskriftsartikel (refereegranskat)abstract
- Analytical protocols for normalization of artifacts and signal quality control are crucial in the design of intensity-based imaging optodes. In this study, we demonstrate how the time correlated pixel-by-pixel calibration (TCPC) technique could be used to predict analytical sensitivity, limit of detection (LOD) and determination of signal variation (relative standard deviation, R.S.D.) at a pixel level throughout measurements without separate tests. In addition, LOD from the TCPC protocol was used to define the operational lifetime of the sensor. The technique was tested on a recently developed imaging ammonium optode. The predicted parameters using TCPC agreed well with the determinations of the parameters using standard analytical protocols. Predicted limit of detection was 0.7 x 10(-6) M compared to 1.3 x 10(-6) M determined through a separate LOD determination. The operational lifetime of the optode was 280 h compared to the actual value of 286 h. When exposed to a soil matrix the operational lifetime was significantly reduced to 128 h. The decrease in sensor performance was efficiently tracked by all the statistical parameters, e.g. during a total experimental period of 234 h, the analytical sensitivity changed from 3 x 10(-6) M to 14 x 10(-6) M between 125 x 10(-6) M and 250 x 10(-6) M. The technique is exemplified by a long-term (similar to 10 days) test of a recently developed ammonium fluorosensor, and high-resolution imaging of ammonium concentrations in porous media following dissolution of a fertilizer stick in soil. (c) 2005 Elsevier B.V. All rights reserved.
|
|
