| 1. |
- Tengberg, A., et al.
(författare)
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Evaluation of a lifetime-based optode to measure oxygen in aquatic systems
- 2006
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Ingår i: Limnology and Oceanography. - : Wiley. - 1541-5856. ; 4:FEB, s. 7-17
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we evaluate the performance of a commercially available lifetime-based optode and compare it with data obtained by other methods. We performed a set of 10 different tests, including targeted laboratory evaluations and field studies, covering a wide range of situations from shallow coastal waters and wastewater treatment plants to abyssal depths. Our principal conclusion is that, owing to high accuracy (+/- 2 mu M), long-term stability (more than 20 months), lack of pressure hysteresis, and limited cross-sensitivity, this method is overall more suitable for oxygen monitoring than other methods.
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| 2. |
- Friedrich, Jana, et al.
(författare)
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Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11, s. 1215-1259
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX (“In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies”, www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences. Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of watercolumn oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.
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| 3. |
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| 4. |
- Ståhl, H., et al.
(författare)
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Respiration and sequestering of organic carbon in shelf sediments of the oligotrophic northern Aegean Sea
- 2004
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Ingår i: Marine Ecology-Progress Series. ; 269, s. 33-48
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Tidskriftsartikel (refereegranskat)abstract
- Respiration and sequestering of organic carbon was investigated in northern Aegean Sea sediments (NE Mediterranean). Benthic total carbonate (C-T, also called SigmaCO(2) or dissolved inorganic carbon, DIC) fluxes and O-2 uptake rates were measured in situ using a benthic lander. Dissolved organic carbon (DOC) fluxes were calculated from pore water gradients, taking into account the influence of biodiffusion/bioirrigation. Macrofaunal biomass was determined in the sediment collected by the chambers of the benthic lander. Chl a distributions were used as a tracer of high-quality sedimentary organic carbon. The measured benthic C-T fluxes were positively correlated with the O-2 uptake rates. The obtained average apparent respiration ratio (C-T flux:O-2 flux) of 0.90 +/- 0.36 suggests a clear dominance of aerobic respiration in these organic carbon-poor shelf sediments. The C-T efflux, the 02 uptake rate, and the DOC flux were significantly higher in spring than in fall at 2 of the stations. The Black Sea water, which enters the Aegean Sea in the study area, did not influence benthic respiration rates or organic carbon sequestering rates. A strong positive correlation between both the C-T and O-2 fluxes and the mean chl a concentration in surficial sediment suggests that benthic respiration, to a large extent, was controlled by the availability of labile phytodetrital organic matter. There was no influence of macrofaunal biomass (dry weight) on C-T fluxes or oxygen uptake rates. The calculated benthic DOC fluxes made up 7.2 to 27 % (average 14 +/- 8.1 %) of the C-T fluxes, indicating that their contribution to the overall recycling of organic carbon in these sediments was important. The organic carbon burial efficiency ranged from 0.1 to 5.3 %, but at Stn KA1 it was considerably higher (average 4%) than at the other stations (average 0.3%). Except for this station, the obtained burial efficiencies were very low compared to other sediments with similar accumulation rates. The average burial flux of organic carbon corresponded to less than 1 % of the annual mean primary production (PP) for the Aegean Sea at Stn KA1, and to less than 0.1 % of PP at the other stations.
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| 5. |
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| 6. |
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| 7. |
- Chu, S. N., et al.
(författare)
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Field evaluation of a low-powered, profiling pCO2 system in coastal Washington
- 2020
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Ingår i: Limnology and Oceanography: Methods. - : Wiley. - 1541-5856. ; 18:6, s. 280-296
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Tidskriftsartikel (refereegranskat)abstract
- Summertime upwelling of deep, corrosive waters on the continental shelf of the northern California Current System can exacerbate ocean acidification conditions, providing unsuitable environments for development of calcifying organisms and finfish that are important to the local economy. To better understand the carbonate system in this dynamic region, two recently developed technologies were combined with other sensors to obtain high-frequency carbon profile data from July 2017 to September 2017. The compact, low-power sensor package was composed of an optical sensor for partial pressure of carbon dioxide (pCO2 optode, Aanderaa model #4797) integrated onto a wave-powered PRofiling crAWLER (PRAWLER). The PRAWLER profiled from 3 to 80 m, stopping at fixed depths for varying lengths of time to allow for pCO2 equilibration. pCO2 derived from a regional empirical algorithm was used to correct optode drift using data at 80 m. Near-surface adjusted optode pCO2 agreed within 6 ± 42 μatm to surface pCO2 from a nearby Moored Autonomous pCO2 instrument. Throughout the water column, optode pCO2 compared to algorithm pCO2 within −28 ± 66 μatm. Overall, optode uncertainty was 35–72 μatm based on root-mean-square errors from all comparison data sets. Errors are attributed to optode calibration, adjustment, algorithm uncertainty, and environmental variability between optode and reference data. Improvements for optode performance within this profiling application include using more stable sensing foils, in situ calibration, and pumped flow over the sensing foil. Additionally, the study revealed undersaturated (corrosive) waters with respect to aragonite below 60 m throughout the deployment that reached up to 40 m by mid-September. © 2020 The Authors. Limnology and Oceanography: Methods published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.
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| 8. |
- Tengberg, Anders, 1962, et al.
(författare)
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Intercalibration of benthic flux chambers II. Hydrodynamic characterization and flux comparisons of 14 different designs
- 2005
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 94:1-4, s. 147-173
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Tidskriftsartikel (refereegranskat)abstract
- We have compared 14 different sediment incubation chambers, most of them were used on bottom landers. Measurements of mixing time, pressure gradients at the bottom and Diffusive Boundary Layer thickness (DBL) were used to describe the hydrodynamic properties of the chambers and sediment-water solute fluxes of silicate (34 replicates) and oxygen (23 replicates) during three subsequently repeated incubation experiments on a homogenized, macrofauna-free sediment. The silicate fluxes ranged from 0.24 to 1.01 mmol m(-2) day(-1) and the oxygen fluxes from 9.3 to 22.6 mmol m(-2) day(-1). There was no statistically significant correlation between measured fluxes and the chamber design or between measured fluxes and hydrodynamic settings suggesting that type of chamber was not important in these flux measurements. For verification of sediment homogeneity, 61 samples of meiofauna were taken and identified to major taxa. In addition. 13 sediment cores were collected. sectioned into 5-10-mm slices and separated into pore water and solid phase. The pore water profiles of disolved silicale were used to calculate diffusive fluxes of silicate. These fluxes ranged from 0.63 to 0.87 mmol m(-2) day(-1). All of the collected sediment parameters indicated that the sediment homogenization process had been satisfactorily accomplished, hydrodynamic variations inside and between chambers are a reflection of the chamber design and the stirring device, In general. pump stirrers with diffusers give a more even distribution of bottom currents and DBL thicknesses than paddle wheel-type stirrers, Most chambers display no or low static differential pressures when the water is mixed at rates of normal Use, Consequently. there is a low risk of creating stirrer induced pressure effects on the measured fluxes. Centrally placed stirrers are preferable to off-center placed stirrers which are more difficult to map and do not seem to give any hydrodynamic advantages, A vertically rotating stirrer gives about five times lower static differential pressures at the same stirring, speed as the same stirrer mounted horizontally If the aim is to simulate or mimic resuspension at high flow velocities, it cannot be satisfactorily done in a chamber using it horizontal (standing) rotating impeller (as is the case for most chambers in use) due to the creation of unnatural conditions. i,e. large static differential pressures and pre-mature resuspension at certain locations in the chamber. (c) 2004 Elsevier B.V. All rights reserved.
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| 9. |
- Bolmsvik, A., et al.
(författare)
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Weather protection at the construction site : Work environment and conditions for moisture and mould growth on massive timber
- 2023
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Ingår i: Journal of Physics, Conference Series. - : Institute of Physics. - 1742-6588 .- 1742-6596. ; 2654:1
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, the use of timber (especially massive timber) has increased worldwide, mainly driven by anticipated environmental benefits. However, there is debate on how to handle the susceptibility against microbial growth for wooden constructions, especially during the construction phase. Sometimes full weather protection is used to avoid exposing the wooden material to outdoor conditions, but oftentimes the structures are fully exposed to precipitation. In an earlier study, one construction site using a full weather protection was studied, and the results showed promising results on the improved hygrothermal conditions and reduced risk of mould growth. Moreover, the site contractor also indicated improved work environment and productivity, however, this was not included in that study. This present study aims to investigate the effects of using full weather protection during construction in seven different construction projects to follow-up and broaden the earlier single project study. The studied aspects include the hygrothermal conditions, potential of mould growth, and influence on the work environment. Temperature and relative humidity were measured and analysed. Samples of cross-laminated timber (CLT) were analysed using a microscope, and the results are compared to theoretical mould growth potential. This is measured both inside the weather protection and outside at the seven construction projects. Furthermore, a work environment questionnaire is distributed to workers at the sites to collect the perceived work environment using a full weather protection. The results of the study partly confirm the conclusions from the earlier study, i.e., reducing the risk of mould growth and causing a slightly warmer and dryer conditions than outside. In addition, the results indicate an improved work environment. The majority of the interviewees wishes a weather protection in their next project regarding the work environment.
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| 10. |
- Granit, Jakob, et al.
(författare)
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A conceptual framework for governing and managing key flows in a source-to-sea continuum
- 2017
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Ingår i: Water Policy. - : IWA Publishing. - 1366-7017 .- 1996-9759. ; 19:4, s. 673-691
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Tidskriftsartikel (refereegranskat)abstract
- Current approaches to environmental protection and development on land, along rivers and coastal zones, and in marine environments are struggling to effectively promote sustainability. This is partly due to limited understanding of how ecosystems are linked, and partly due to fragmented governance and management arrangements in the continuum from source to sea that hinders cooperation and strategic overview across connected systems. Meanwhile, the key flows that link ecosystems are being altered by climate change and by an intensification of human activities, which are also expanding offshore where management regimes are typically weak or nonexistent. This paper presents a conceptual framework to guide the design of future initiatives aimed at supporting green and blue growth in source-to-sea systems. It includes a taxonomy of key flows, elements to guide analysis and planning and a common framework for elaborating a theory of change. Assembling a governance baseline and engaging stakeholders are critical elements in the approach. The conceptual framework builds on recent experiences of pro-sustainability action in source-to-sea systems around the world, and the paper applies the theory of change framework to selected case studies in order to develop further insights.
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