| 1. |
- Angove, Charlotte, et al.
(författare)
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Assessing the efficiencies and challenges for nutrient uptake by aquatic plants
- 2018
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 507, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- Aquatic plant meadows are valuable components to the 'coastal filter' and it is important to understand the processes that drive their ability to cycle nutrients. However, at present, the field-based evidence for understanding the drivers of nutrient uptake by plants is lacking. This study aimed to investigate how well individual shoots of aquatic plants could meet their nitrogen demands using the sediment nutrient pool (porewater ammonium) and to explore which traits helped to facilitate such uptake. Several species were investigated in shallow, submerged (2-4 m) mixed-species communities in the northern Baltic Sea using incubation experiments with enriched ammonium. After a 3.5 h incubation time, individuals were collected and analysed for nitrogen (% DW) and N-15 (at-%) concentrations. Uptake by plants was calculated per unit nitrogen in response to the N-15 labelled source and to overall nitrogen availability. Background porewater ammonium availability was highly variable between individual plants. Species identity did not significantly affect uptake metrics and the effect of ambient porewater availability was weak. As biomass increased there were significant logarithmic declines in the 95th quantiles of nutrient uptake rates, ambient porewater nutrient availability and aboveground nitrogen tissue concentrations (% DW). Such findings suggested that uptake rates of plants were significantly demand driven and the nutrient conditions of the porewater were significantly driven by the demands of the plant. Findings parameterised the unfulfilled potential for some aquatic plants to cycle nutrients more efficiently and highlighted the potential importance of access to new nutrient sources as a way of enhancing nutrient cycling by aquatic plants. Plant traits and community properties such as the activity of infauna could facilitate such an access and are likely important for nutrient uptake.
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| 2. |
- Carney Almroth, Bethanie, 1974, et al.
(författare)
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Warmer water temperature results in oxidative damage in an Antarctic fish, the bald notothen
- 2015
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 468, s. 130-137
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Tidskriftsartikel (refereegranskat)abstract
- Global climate change is predicted to result in increases in water temperature in the polar regions, but the full consequences of this for marine fish species are not understood, especially with regard to cellular mechanisms underlying oxidative stress. Warmer temperatures could potentially result in increased oxidative stress, and it is not known whether stenothermal fish can cope with this on a cellular and physiological level. In order to address this, we exposed bald notothen (Pagothenta borchgrevinki), a fish species endemic to Antarctica, to an increase in temperature from -1.6 degrees C to 4 degrees C and measured the effects on oxidative stress including antioxidant defenses, oxidative damage in proteins and lipids, and transcriptional regulation of involved genes. We show that the fish responds to an acute (12 h) temperature increase with increased antioxidant defenses. However, these antioxidant defenses were similar to basal levels following long-term (3 weeks) exposure to the higher temperature and moreover, these individuals also had higher levels of oxidative damage. These results indicate that this species has the ability to alter levels of endogenous antioxidants, but that this response is transient and insufficient to protect against oxidative damage. These effects may have serious consequences for these fish in a warmer future since long-term consequences of this accumulation of damaged lipids and proteins are associated with aging and known to include decreased cellular function, disease and eventually cell death. (C) 2015 Elsevier B.V. All rights reserved.
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| 3. |
- Felisberto, Paulo, et al.
(författare)
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Acoustic monitoring of O-2 production of a seagrass meadow
- 2015
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 464, s. 75-87
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic data were acquired in October 2011 over a Posidonia oceanica meadow in the Bay of la Revellata, Calvi, Corsica. The purpose was to develop an acoustic system for monitoring the oxygen (O-2) production of an entire seagrass meadow. In a shallow water area (<38 m), densely covered by P. oceanica, a sound source transmitted signals in 3 different bands (400-800 Hz, 1.5-3.5 kHz and 65-8.5 kHz) toward three self-recording hydrophones at a distance of 100 m, over the period of one week. The data show a high correlation between the diel cycle of the acoustic signals' energy received by the hydrophones and the temporal changes in water column O-2 concentration as measured by optodes. The results thus show that a simple acoustic acquisition system can be used to monitor the O-2-based productivity of a seagrass meadow at the ecosystem level with high temporal resolution. The finding of a significant production of O-2 as bubbles in seagrass ecosysterns suggests that net primary production is underestimated by methods that rely on the mass balance of dissolved O-2 measurements.
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| 4. |
- Gerecht, A. C., et al.
(författare)
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Phosphorus availability modifies carbon production in Coccolithus pelagicus (Haptophyta)
- 2015
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 472, s. 24-31
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Tidskriftsartikel (refereegranskat)abstract
- Abstract The coccolithophore Coccolithus pelagicus (Wallich) Schiller fixes CO2 into particulate organic carbon (POC) through photosynthesis and into particulate inorganic carbon (PIC) in the form of calcite. To examine the role of phosphorus (P) availability in the production of POC and PIC, C. pelagicus subsp. braarudii (Gaarder) Geisen et al. was grown in semi-continuous cultures at three initial phosphate concentrations (P-replete, 1, and 0.5 μM [P]). Reduced P-availability (1 and 0.5 μM [P]) decreased POC production, while PIC production only decreased when phosphate concentrations became growth limiting (0.5 μM [P]). This decrease has not been observed previously in batch cultures, highlighting the inadequacy of the batch culture approach with regard to determining carbon production. The reduction in growth rate by 50% at 0.5 μM [P] was accompanied by a doubling in cell volume (and POC). PIC production was halved, resulting in a lowered PIC to POC ratio. The average number of coccoliths per cell (and PIC content) remained the same among treatments, despite the significant change in cell size. Our data suggest that POC production in C. pelagicus is more sensitive towards a moderate reduction in phosphorus availability than PIC production. Once phosphorus availability limits cell division, however, phosphorus resources are invested into POC rather than PIC production. This reduces cell density and sinking rates, indicating that coccoliths do not act as ballast for reaching deeper nutrient-rich layers under nutrient limitation.
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| 5. |
- Kutti, Tina, et al.
(författare)
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Metabolic responses of the deep-water sponge Geodia barretti to suspended bottom sediment, simulated mine tailings and drill cuttings
- 2015
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 473, s. 64-72
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Tidskriftsartikel (refereegranskat)abstract
- Northeast Atlantic sponge beds are recognized as local hotspots for biodiversity and nutrient cycling. Despite their important functional role little is known about their sensitivity to effluents from the expanding hydrocarbon-, mining- and bottom trawling industry. Here, data on physiological and biological responses of the common demosponge Geodia barretti to short (4 h) and long-term (50 day) cyclic exposure of suspended particles are presented. The laboratory study showed that 4 hour pulse exposures with crushed rock particles at 500 mg l(-1) caused a 50% drop in oxygen consumption but with a quick recovery to pre-exposure oxygen consumption once suspended sediment loads returned to background levels. Long-term cyclic exposure (12 h each 24 h) for 29 days caused a permanent drop in oxygen consumption with 60% in sponges exposed to 50 mg l(-1) of crushed rock but with no apparent effect on the energy content of the sponge. Oxygen consumption and energy content of sponges exposed to natural bottom sediments at the same concentration remained unchanged. In conclusion, G. barretti appears to have well developed mechanisms to resist sediment stress, however, the study demonstrated that operations releasing large amounts of suspended crushed rock such as exploration drilling and submarine tailings disposal near sponge beds should be carefully planned to avoid long-term losses of benthic ecosystem functions, such as organic matter re-mineralization.
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| 6. |
- Villnas, Anna, et al.
(författare)
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Multi-level responses of Macoma balthica to recurring hypoxic disturbance
- 2019
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 510, s. 64-72
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Tidskriftsartikel (refereegranskat)abstract
- The frequency of seasonal and short-term hypoxia is increasing in coastal seas. How such repeated disturbances affect key species that have important roles for ecosystem processes and functions remains, however, unknown. By performing a field experiment we explored if the bivalve Macoma balthica can cope with short-term, recurring hypoxic stress, and investigated how hypoxia affects the condition of surviving bivalves. By combining data on different levels of biological organization, i.e., on physiology (biomarker response), behaviour and demography, we identified stress responses before the population declined. One pulse of hypoxic disturbance (3 days) resulted in behavioural alterations, as adult M. balthica extended their siphons, emerged towards the sediment surface and expressed decreased reburial rates. However, the demographic structure of the population remained unaltered. Several pulses of recurring hypoxic stress resulted in physiological response with changes in glutathione reductase and acetylcholinesterase enzyme activities. The recurring hypoxic disturbance was observed to affect juvenile bivalves before adults, while pro-longed hypoxia reduced the entire bivalve population. Our results clearly show that hypoxic stress changes the behaviour and physiology of M. balthica before demographic changes occur, which is likely to have severe implications for the contribution of this key species to ecosystem functioning. That a combination of measures at different levels of organization can detect disturbances at an early stage suggests that such an approach would be useful for assessing the effects of disturbances on marine ecosystems that are increasingly affected by anthropogenic change.
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| 7. |
- Eriander, Louise, 1984, et al.
(författare)
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Assessing methods for restoration of eelgrass (Zostera marina L.) in a cold temperate region
- 2016
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 479, s. 76-88
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Tidskriftsartikel (refereegranskat)abstract
- More than 50% of eelgrass habitats have disappeared from the Swedish NW coast in the last 30 years. Restoration is being proposed to assist recovery but little is known regarding methods suitable under Scandinavian conditions; e.g. short growing seasons and scouring by ice. In the present study we evaluated different restoration methods using shoots and seeds in a Swedish fjord and assessed if eelgrass could be successfully transplanted between sites with different depth and exposure. The study demonstrates that both shoot- and seed methods can be successfully used to restore eelgrass at this latitude. Survival and growth of unanchored single shoots, transplanted without sediment in shallow habitats (1.0–1.5 m) was very high (> 500% increase in shoot density after 14 months). This restoration method showed 2–3.5 times higher growth rate and was 2–2.5 times faster compared with shoots anchored in the sediment and shoots transplanted in sediment cores, respectively, and is recommended for shallow habitats in Sweden. Growth within deeper habitats (3.0–4.5 m) was substantially lower (40% loss to 50% increase) due to light limitations and high winter mortality. Restoration using seeds distributed from mesh-bags showed very low seedling establishment rates (approximately 1%) making this method less cost-effective than transplanting single shoots in shallow habitats. However, growth of seedlings was high and this method is recommended for deep habitats with soft sediment where shoot transplantation is difficult. Despite dramatic differences in eelgrass morphology between habitats with different depth and exposure, all shoots within a planting site had the same morphology at the end of the study, independent of origin. A baseline genetic survey supported that the observed changes in morphology of transplants were due to a plastic response, suggesting that donor populations do not have to exactly match the morphology of the plants targeted for restoration.
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| 8. |
- Eriander, Louise, 1984
(författare)
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Light requirements for successful restoration of eelgrass (Zostera marina L.) in a high latitude environment – Acclimatization, growth and carbohydrate storage
- 2017
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 496, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- The short growth season in high latitude environments pose challenges for eelgrass restoration, particularly in areas that receive little light due to e.g. depth or reduced water quality conditions. In order to improve our understanding of the acclimatization potential of eelgrass to low light and the light requirement for successful restoration of eelgrass, an indoor mesocosm study was performed assessing three light (3, 5 and 10 mol photons m−2 day−1) and two temperature conditions (12 and 20 °C). The aim of the study was to determine if eelgrass transplants originating from a shallow donor meadow with high light could acclimatize to low light conditions and how different light conditions affect growth characteristics and carbohydrate storage of transplants. A second aim was to investigate how eelgrass grown under different light conditions cope during severe shading (zero light) under the two temperature conditions, and how severe shading affect the carbohydrate stock of transplants. The results demonstrate that eelgrass can acclimatize to light levels from 10 down to 3 mol photons m−2 day−1 by adjustments in morphology, pigmentation and growth strategy, but with a significant reduction in the production of lateral branches below 5 mol photons m−2 day−1. Temperature had a strong positive effect on shoot morphology and above ground biomass production independent of light treatment, but less effect on branching. Furthermore, the study shows that acclimatized eelgrass transplants can store carbohydrates at light levels down to 3 mol photons m−2 day−1, but that losses occur in relation to the transplantation process and as a result of severe shading. Survival of transplants during severe shading conditions demonstrated large temperature dependent effects, with no effects of previous light conditions. The results from this study provide important insight into the phenotypic response by eelgrass to environmental conditions and could have important implications for management and restoration of eelgrass in high latitude environments with respect to acclimatization potential and the minimum light requirement for successful restoration.
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| 9. |
- Frommel, A. Y., et al.
(författare)
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Ocean acidification has lethal and sub-lethal effects on larval development of yellowfin tuna, Thunnus albacares
- 2016
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 482, s. 18-24
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Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification (OA), the process by which increasing atmospheric CO2 is absorbed by the ocean, lowering the pH of surface waters, has been shown to affect many marine organisms negatively. It has been suggested that organisms from regions with naturally low pH waters, such as upwelling areas, could serve as models for future effects of OA and may be adapted to increased pCO(2) levels. In this study, we examined the effects of OA on yellowfin tuna, a highly pelagic species that spawns in the eastern tropical Pacific, an area that includes regions of strong upwelling events. Larvae reared at decreasing pH levels (pH 8.1, 7.6, 7.3 and 6.9) showed increasing organ damage in the kidney, liver, pancreas, eye and muscle, which correlated with decreased growth and survival. These findings complement earlier studies on organ damage in Atlantic cod and herring larvae and demonstrate that OA may have detrimental effects on fish larvae, regardless of their pre-exposure to low pH waters.
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| 10. |
- Gilbert, F., et al.
(författare)
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Redox oscillation and benthic nitrogen mineralization within burrowed sediments: An experimental simulation at low frequency
- 2016
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 482, s. 75-84
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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.
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